Mwl Marco

 NUTRITION IN ANIMALS

NUTRITION AND FOOD NUTRIENTS
Nutrition is the process by which an organism takes in and uses nutrients or
 Is the way in which organism obtain the raw materials they need to live.

It involves all the process by which nutrients are ingested, digested, absorbed and later on converted into the body’s organic compounds and energy
Living organisms are regarded as working machines which requires a continuous supply of energy.
The energy which is supplied to the body of living organisms comes from nutrients which come from the food organism consume. The energy enables the organism to work and stay alive           .Importances of nutrition in living things;
a. Nutrients are required   for growth and  development
b .Nutrients are required by the body to replace, repair of worm out and damaged tissues.
c. Nutrients are required for protection against diseases.
d. Nutrients are required  for contraction and relaxation of muscles
e. Nutrients are also needed in electrical transmission of nerve impulses.
f. Nutrients are needed for the maintenance of a constants body temperature                                             There are two types of Nutrition.
·       -Autotrophic nutrition. (self-feeding)
·         -Heterotrophic nutrition.

Autotrophic nutrition
Autotrophic Nutrition is a mode of nutrition whereby organisms manufacture their own food from simple inorganic substances such as carbon dioxide and water.
Eg. Green plants manufacture their own food through the process of photosynthesis.

Heterotrophic Nutrition.
Heterotrophic Nutrition is the mode of nutrition whereby the organism get nutrients by eating other organisms
Animals (including humans) are heterotrophs.
 Heterotrophs take in food and digest it ( break it down) into simple substances that can be absorbed and used by the body.
    substance can  be called food if it provides the body with one or more of the following:-
   a source of energy.   material for growth and repair , Factors for good health and Food substance provides the nutrients which are highly needed by the body of living organisms such as human being.
The nutrients eaten by man includes  carbohydrates, fats    proteins ,  vitamin,    mineral salts 
andWater is not thought as nutrient, but it is an essential part which dissolves the food nutrients; so that, they can be digested and absorbed.

Heterotrophic Nutrition
It is divided into:  Saprophytic, holozoic, commensalism and mutualism and parasites.
Heteromorphism is divided into Symbiotic nutrition & holozoic nutrition.

1. Symbiotic nutrition.
Symbiosis (living together) is an association of two or more organisms of different species living together and interacting with each other.
Types of symbiosis:- i) parasitism. ii) Commensalism. iii) Mutualism. iv)saprophytic
i) Parasitic nutrition: where by organism (parasite) obtain their nutrients or food from the tissue of another organism(host).Parasite are of two types:
a)Endo parasites: Live inside the host, eg.: liver fluke ,tapeworm ,plasmodium.
b) Ecto parasites: live in external surface of the host, e.g. fleas, ticks, mice.
-parasite can also be sub-divided into:
a)facultative parasites: they live in or on the host and also in organic remains. It can continue living after the host dies. It can live with or without the host, e.g. fleas.
b)Obligate parasites: They live only in or on the host. The parasite dies with the host. E.g. roundworms, tapeworm, mistletoes.
ii. Mutualism (symbiotic): Is an association of two or more organisms of different species where both or all organisms benefit. Eg. Ruminants and bacteria, leguminous plants and the nitrogen fixing bacteria.
iii. Commensalism: Is an association of two organisms of different species in which one of the organisms gains (commensal) while the other neither gains nor losses.
Eg:       a) The white cattle egret and the cattle
b) Bacterium Escherichia coli and the man (Escherichia coli in the intestine obtains food and shelter while the man neither losses nor gains.
iv) saprophytism; Where by organisms obtain their food from dead organic matter. They are called saprophytes. Eg: fungi (mushroom) and some bacteria

2. Holozoic nutrition :
This is the type of nutrition where by solid complex food substances are obtained, ingested, digested, absorbed and assimilated.
Types:
i) Carnivorous mode of feeding: is a mode of feeding whereby an organism feeds on other animals They eat the flesh of animals, Example of carnivores  cats & dogs
ii) Herbivorous mode of feeding: is a mode of feeding whereby an organism feeds on plants.Examples of HerbivoresT cattle, horse, rabbits.
iii) Omnivorous mode of feedin: is one in which an organism feeds on both plants and animals Examples of Omnivores man & pig

Saprophytism: is a relationship in ewhich an organism absorbs nutrients from dead organic matter. Example mushroomThese are organism which feed on dead or decaying organic matter or materials.
Saprophytes are divided in Decomposers and Detritivores
Decomposers make dead organic matter rot.
Detritivores – Animal that consume detritus i.e particles

    Human Nutrition;
a diet.he sum total of all the food an organisms eats in a meal on a regular basis 

 Balanced diet is the diet that provides the body with all nutrients and  in the right  proportion . These nutrients are required in proportion to:- age, Sex, body size (weight), health conditions and state of activity (occupation) of the individual

Different types of food substances and their function in human body:
  The body of a human being requires different types of food substances in order to carry its functions properly.
These food substances are:-
·         Carbohydrates
·         lipids (fats and oils)
·         Proteins
·         Vitamins
·         Mineral salts
·         water
1.      Carbohydrates:
Carbohydrates are compounds of carbon, hydrogen and oxygen in ratio of CH₂O=1:2:1.
Carbohydrates are referred as the energy giving food.

figure.  different types of food

Function of carbohydrates are
-energy giving food,
-helping in digestion
-building materials (cellulose in plants)
-chitin (polysaccharide)=exoskeleton of arthropods.
Types of Carbohydrates
a)Monosaccharides  (formula  C₆H₁₂O₆. This includes:
i)Glucose : eg from sweet fruits ,in honey & blood.
ii) Fructose eg: sweet fruits & nectar.
iii)Galactose :milk

Properties of monosaccharides:
 i) Soluble in water.
ii) Sweet tasting 
iii) Crystallisable.

b)Disaccharides:(formular;C₁₂H₂₂O₁₁
They are formed by joining two simple sugar molecule (monosaccharides with the loss of one molecule of water by the process of condensation.

Disaccharides can be broken down into their constituent monosaccharides by process of Hydrolysis, eg. Sucrose to glucose and fructose.
Examples of disaccharides are;-
i. Sucrose (cane Sugar) = sugar cane and sugar beet. (glucose + fructose.)
ii. Maltose (malt sugar) = Germinating seed, (glucose + glucose.
iii. Lactose (milk sugar) (glucose + galactose)

Properties of disaccharides
 i. Soluble in water
  ii. Sweet tasting
    iii. Can crystallise
NB. Complex reducing sugars are disaccharides that reduce CuSO4 in Benedict’s solution when heated together.
            - Non-reducing sugar are disaccharides that do not reduce CuSO4 in Benedict’s solution when heated together.

C. Polysaccharides. Formular: (C₆H₁₀O₅)n
They are formed by joining very many simple sugar molecules. (Many monosaccharides). Example of polysaccharides are:
i. Starch –stored form of carbohydrates in plants.
ii. Glycogen-stored form of carbohydrates in animals. In liver and muscles.
iii. Cellulose-in cell wall of plants.
Sources of starch:
 i. Cereals-maize, rice, millet, wheat
ii. Root crops-cassava, sweet potato, Irish potato 
iii. Leguminous seed-beans and peas.

FUNCTION OF CARBOHYDRATES
-  Carbohydrates provide the body with energy in the body example. Glucose which is the main source of energy.
-Some carbohydrates provide dietary fiber example. Cellulose.
-Carbohydrate combine with protein and lipids to form glycoproteins and glycolipids which are important components of cell membrane.
2.  Proteins:
Proteins molecules are made up of chains of smaller molecules (called amino acid) linked together.
When many amino acids are linked together polypeptides are formed when groups of polypeptides come together they form proteins.
Proteins are referred as nitrogenous compound because of presence of nitrogen
-           Proteins can be obtained from animal and plants sources.
-          Proteins have the same elements as carbohydrates in addition to nitrogen and sometimes phosphorus and sulphur.
-          The main sources of animals proteins are beans, eggs, groundnuts meat from fish, insects, protein are milk, cheese birds and mammals.
-          Other sources of animal protein are milk, cheese and eggs

Figure.Protein

Function of Proteins
-          Proteins are used for growth and repair of the human body.
-          Proteins can be used to provide energy when the body rules carbohydrates and fat.
-          Defense proteins make antibodies which provide the body with immunity against diseases.
-          Functional units: Proteins perform many and specific functions in the body eg. Enzymes, hemoglobin; Hormones, Fibrinogen.
-          Structural components some proteins are components of various structures eg. Muscles fibre, hooves, nail, hair. Feathers etc.
-          It is a component of respiratory pigment eg. myoglobin found in muscles. Therefore, it is vital in the transport and distribution of oxygen within the body.
-Enzymes which help us to digest food are protein in nature  
3. LIPIDS
These compounds contain carbon, hydrogen and oxygen but in different proportion to those in carbohydrates.
-          Lipids are insoluble in water and are said to be hydrophobic (water – hating)
-          lipids occur in two forms
       Fats and oil.
-           Oils are liquid at relatively low temperatures where as 
         fat are solid.
-          The main sources of fat are milk and animal fats, groundnuts, coconuts and oyster nuts.

Figure. A lipids

Functions of Lipids
·         Sources of energy. During the process of respiration, lipids can be broken down to release energy required by the body.
·         Sources of metabolic water. When fats and oil are oxidized they yield water as well as energy.
·         Offer protection- fats protect the organs such as kidney, heart and act as shock absorber.
·         Insulation- fats which are deposited below the skin prevents heat loss from the body.4.       Vitamins:

-           Vitamins are organic compounds which are synthesized by both plants and animals.
-          Vitamins help to keep the body health but are required only in very small quantities.

Vitamin	Source	Functions	Deficiency Disorder
A(Retinal)	Liver, milk, egg,yolk,animal fat	cell growth forms visual pigment	-night blindness (poor night vision)
B1 (thiamine)	Egg-yolk beans, unpolished cereals	Enzyme activity, in aerobic respiration.	Beriberi
B2(Riboflavin)	Egg york, vegetables, unpolished cereals	Normal functioning of nervous system and gut.	Crack aand sores around the mouth nd nose
B3.(Niacin)	nuts, meat, fish	Needed by many enzymes	Pellagra
B6(Pyroxine)	Fish, cereals,yeast	Essentials in protein metabolism	anaemia
B12(Cyanocobalamin)	Fish, cereals,yeast,Milk	Help to formation of red blood cells	weight loss
Vitamin C(ascorbic acid)	Citrus fruits, fresh green, tomatoes	Antioxidant	Scurvy
Vitamin D(Calciferol)	Egg york,milk,oilyfish	Hel to build and maintain teeth and bones	Ricket in children
VitaminE(Tocopherol)	Corn.or sunflower oil	Antioxidant	Infertility in rats
VitaminK.	Green vegetable and liver	Needed for normal blood clotting	Defective blood coagulation resulting in excessive bleeding

5.  Mineral salts
Mineral salts are organic compounds containing elements, which are essential for normal body metabolism.There are two types.
1.Macrominerals-These required in relatively large quantities in the body
2.Microminerals(trace element) -These are required in very small quantities and

A. Element	Sources	Principal function (s)
Calcium ( Ca)	Milk, Yoghurt, green vegetables, Cheese and eggs	Help to build strong bones and  teeth, -muscle  contraction nerve impulse, - blood dotting Deficiency.Bleeding easily, weak bone
Chlorine l	Table salt   Sea foods	-Maintaining of tissue fluid.Formation of hydrochrochric acid in stomach     .Deficiency.Poor digestion of protein .
Zinc	-Oysters, Shrimp, crabs,meat,	-Help to heal wound Deficiency- impaired taste
Iron , Fe	liver, green vegetables, eggs, beans and green vegetable	Formation of hemoglobin (red pigment in blood cells that  carries oxygen) Deficiency-Anaemia
Magnesium, Mg	Spinach, pumpkin,seeds and black beans	Health bones and teeth, muscle contraction Deficiency-Muscles weakness, and irregular heart beat
Sodium Na	Table salt	Nerve and muscle activity Deficiency-Muscle cramp
Phosphorus, P	Protein foods	Health bones and teeth, synthesis, production of ATP

6.  Water
Water is a compound of hydrogen and oxygen and forms about 90% of the cell. Water acts as a medium for many biochemical reactions.
Properties of water.
•          Water is a universal solvent
•         Water has a high heat capacity
•         Water has high surface tension
Function of water
•                      Water forms a large proportion of cytoplasm; where by most chemical reactions take place in the cell which contains much cytoplasm.
•                     Nutrients and waste materials hormones and other important chemicals are transported around the body in solution i.e mainly is blood.
•    Water is needed for the hydrolysis reactions involved in the digestion food.
•     Water maintains the shape of cells and organs
•    Water helps in the cooling process of the body through evaporation of sweat.
•     Water acts as a lubricant by reducing friction between surfaces that rub against one another. eg. eyelids and eyeball.
•    Essential for many biochemical reactions in the cell.
Balanced Diet
Diet is the sum total of all the food an organism eats in a meal on a regular basis
Balanced diet: Is a diet which contains all the types of food substances in their right proportion eg. Protein, carbohydrates, vitamin
Any balance diet must provide the body with enough of the following;-
•         Energy from carbohydrates and fat after respiration
•         Materials for growth and repair from proteins
•         Vitamins which help in running the metabolic processes.
•         Water for transporting materials
•         Roughage.
Nutritional requirement for different group of people;
Nutritional requirements of human vary according to age, sex, level of physical activity and state of health.
The groups can be divided into:
•          Male and female
•         Expectant and lactating mothers
•         Children – babies
•         Toddlers and childhood
•         The elderly
•         The sick
•         Sedentary works
•         People living with HIV/AIDS
Expectant and lactating mothers:

Expectant mothers require more food than normal with high amount of proteins for the growth and development of foetus. They also require vitamins as protective foods.
Expectant mothers do not need additional energy or food components until the last 3 months.

 Lactating mothers require food which will stimulate production of milk for baby.
Protein food is recommended.
Folic acid and B vitamin help to lower the risk of birth defects as spina bifida(is disorder characterized by a hole in spine)
Calcium helps in the development of the foetus or baby's bones
Zinc is important for the proper progression of labour and proper growth and development of the baby
They requires adequate amounts of dietary fibre to reduce the likelihood of constipation which is a common complaint during pregnancy.
The mother require iron for her blood supply needs

Babies;

The babies’ feeds on mother’s milk which contains all the requirement needed. The mother milk contains colostrum which provides the balanced diet for both male and female become it has essential material for growth and development.

    Manual workers:
These people are labourers who do hand manual work eg. Quarrying construction sites, builders etc.
These people should take a lot of energy giving food eg. Stiff porridge (ugali).
Young children
 Young children need a balanced diet with high proportion of proteins.
Children need to grow they also need food with high nutritional value of vitamins to protect them from diseases.

   Elderly
Elderly people need less food than younger people became they are less active.
   Elderly need food with high nutritional Value of vitamins and proteins to make their bodies repair worn out and damaged tissues and maintain a state of good health.
   The sick: eg people living with HIV/AIDS.
This group requires the food rich in vitamins, proteins and carbohydrates.

   Sedentary workers.
These are people who work long hours, seated in the offices eg. Secretaries.  They require low quantity of energy giving food. Balanced diet is also important to them

NUTRITIONAL DEFICIENCIES AND DISORDERS
Nutritional deficiencies and disorders in human beings

Malnutrition can be quantitative deficiency, i.e. lack of enough food to eat (starvation) which cause marasmus.

Qualitative deficiency: Lack of right kinds of food, thus. Lack of protein leads to kwashiorkor.

Causes of Malnutrition.

1. Low agricultural food crop out put may be due to the following;

-Unfavourable weather condition, lack of rain or flooding.

-Pest and diseases.

-Lack of land or infertility of land.

-Too expensive agricultural inputs-fertilisers and equipment.

-Lack of agricultural knowledge.

-Laziness of people.

2. Lack of money for sufficient food, ie. low salary or too big family, lack of employment.

3. Ignorance regarding food requirements (balanced diet)

4. Religion/beliefs: Taboos excluding some food from certain people; eg

-Some tribes, pregnant women do not eat eggs.

-Muslim do not eat pork (may be replaced with plant protein)

5. Availability of food: growing one type of food only.

6. Spending too much money on beer, clothing and other luxuries.

 Malnutrition is a nutrition disorder caused by the lack of balanced diet.

Malnutrition can be result of the following:
•         Supply of too little of all nutritional requirements
•         Supply of too much of all nutritional requirements
•         Eating only some of the food requirements and ignoring others.

Effects of Malnutrition.                      

1.  Inefficiency: People are not able to work properly.

2. Lack of resistance to diseases and power to overcome it.

3.Death- Pneumonia and measles are great killers under condition of malnutrition

NUTRITIONAL DISORDER
Are conditions of ill health in a person which arise as aresult of lifestyle(pooreating)
  1.Obesity
Obesity means overweight
•         It is caused by taking a lot of carbohydrates, fats and oils than what the body requires
•         Obesity causes high blood pressure and heart diseases.
Symptoms of obesity
•          Increased body weight and mass.
•         High blood pressure
•         Diabetes
•         Gallstones
•         Stroke
•         Heart diseases
Control measures
•         Physical exercises and slimming diet
•         An obese should eat diet with more vegetables and fruits, lean meat and little of carbohydrates
•         Avoid eating too much fatty or oily foods.    
   Anorexia Nervosa(slimmer’s diseases)
Anorexia Nervosa is a self – imposed starvation. That means a person who can get food decides not to eat because he/she fears fatness.
Symptoms of Anorexia Nervosa)
•         Loss of Body proteins which results in to severe loss of weight
•         Lack of menstrual periods (a menorrhoea)
•         Decreased heart beat
•         Decreased skin pigmentation
•         Reduction in size of uterus
•         Weakened muscles and fainting.
BULIMIA NERVOSA
Involves eating followed by effort to remove the food from the body.These efforts could involve self- induced, vomiting, fasting, excessive exercising or taking drugs that stimulating emptying of the bowels or excessive urination.
EFFECTS OF ANOREXIA AND BULIMIA
-Heart problem due to weak cardiac muscles or imbalance of mineral salts
-There are impaired mental function because the brain lacks adequate amounts of glucose
Treatment for Anorexia Nervosa
•         Most severe cases are treated in the hospital with a caring but strict regime in which weight gain
NUTRITIONAL DEFICIENCIES
These deficiencies arise when the body does not have sufficient supply of a  particular food or nutrients. The commonly are
1.Kwashiorkor
is caused by deficiency of protein. It affects children, mostly after stopping to breast feed.
Symptoms of Kwashiorkor
•          Stunted growth as a result of protein deficiency
•         Hair progressively change in texture and becomes soft
•         Hair pigmentation  changes the black pigment melanin decreases
•         Hair is easily plucked off
•         Protruding stomach and swollen lower parts of limbs (caused by the accumulation of  body fluids)
•         Skin becomes dry and cracks easily
•         Weakness and sleepiness
•         Loss of appetite and usually develop
•         Diarrhoea
•         Child becomes anemic and weak
Treatments
is treated by providing a child with a diet that has  adequate amounts of protein
2. Marasmus
This deficiency disease is common in children especially infants.
•         It is caused by general lack of food particularly the protein rich food needed to build up the body.
Symptoms of Marasmus:
•         Stunted   growth
•         The tendency to eat a lot of food when it is available because of hunger
•          The child experiences a tendency of crying continuously  and   being unhappy due to  hunger
•         The victim child becomes thin due to loss in weight
•         The child’s buttocks shrink due to break down of body tissues
Treatments
Getting adequate amounts of food that contains all the nutrients in the right proportion

3. Rickets.

Lack of vitamin D.

Symptoms: 

-Bow less or knock knee.

-Spinal curvature.

Box like appearance of the head with protruding forehead.

.

-Enlarged wrist, knees and ankle joints.

-Delayed eruption of teeth.

Prevention

is prevented by increasing the amount of Vitamin D phosphate and clcium in the diet and by ensuring exposure to sufficient amount of sunlight

Vitamins B1 (Thiamine)
Deficiency of this vitamin results into:
•         Loss of appetite
•         Weakness of limbs
Disease caused is Beriberi Vitamin B2 (Riboflavin)
Vitamin B2 (Riboflavin)
Deficiency symptoms of this vitamin constitute a disease called pellagra
Symptoms:
Poor growth of blood vessels in the cornea of the eyes
Retarded growth in children

Vitamin B12: Cynocabalamine/folic Acid)
Deficiency symptoms include:-
•         Formation of abnormally large red blood cell this leads to pernicious anaemia
•         Nerve disorder
•         Anaemia –especially during pregnancy.

Vitamin C. (Ascorbic Acid)
Disease caused is scurvy.
Symptoms
•         Gums become tender, easy to bleed and teeth become loose
•         Wounds take long to heal
•         Painful and swollen joints
Vitamin D (Calciferol)
Disease caused is Rickets
(Bone deformation)

 Vitamin K (Phylloquinone)
Deficiency symptoms for vitamins K include:
·         slow  clotting of the blood
·         Prolonged bleeding in case of injury
·         Internal bleeding

Mineral deficiency
•          Iodine- Deficiency of this element results into the enlargement of the   thyroid  glands : This is known as Goitre.
•         Potassium- Deficiency of this  mineral element results in
•      Retarded  growth
•   Failure of muscles to contract
•   Paralysis of the body
•         Magnesium –Poor formation of bones and teeth
-failure of muscles to contract
-Behavioral disturbances
-Growth failure
   4. Sodium    
  -Muscle cramps
   -Apathy
    -Reduced appetite

          5.  Chlorine    
  -poor protein digestion
    -Body’s failure to kill the harmful bacteria

    6.Phosphorous 
-Poor formation of bones and teeth
   -Failure of muscle to contract.

DIGESTIVE SYSTEM IN HUMAN

Definition of Terms;
•         Digestion: 
 Is the process by which food is broken down mechanically and chemically into soluble and diffusible form in which it can be absorbed and assimilated in the body.
•         Ingestion:    This  is the process of taking food into the mouth. It involves both mechanical and chemical
•         Mechanical or physical digestion: Large food particles are mixed with saliva, Chewed and broken down and rolled into bolus.
•         Chemical digestion;  - This  involves the use of chemicals i.e. enzyme produced in the  digestive system to break down the stuffs carbohydrates ,protein and fats into smaller molecules particles ready to be absorbed by the cells of the body
•         Absorption: This is the process by which soluble end product of digestion such as amino acid, sugar and fat diffuse into the blood system
•         Egestion- This is the process by which undigested food particles are removed from the body through anus. 
•         Assimilation:  This is the incorporation of products of digestion into the cell metabolism i.e how those end products are used in the body.
Roles of Assimilation
•          Provide glucose needed for respiration.
•         Excess glucose is converted in the liver to glycogen and stored in the liver and muscle cells.
•         Fatty acids and glycerol combine to form facts for storage. Fats are used for insulation, shock absorber for visceral organs eg. Kidney and heart. Fats provide energy in absence of carbohydrates.
•         Water and mineral salts absorbed in the colon are used in body metabolism.
•      Egestion.  Is the removal of undigested or indigestible and unabsorbed food materials from the body usually as feaces.
PARTS OF THE DIGESTION SYSTEM
The human digestive system consists of the  alimentary canal and the associated glands; the liver and the pancreas.
The alimentary canal is a muscular tube which  starts at the mouth and ends at the anus.
1.Mouth .Receiving ingetion foods
2.Oesophagus-  Passes food from the mouth to the stomach.
3.Stomach  -  Receives food from  oesophagues and empties it into the duodenum
4.Small intestine  -  Divide into the duodenum and the ileum. These are sites for digestion and absorption of  nutrients
5. Large intestine  -  this includes the following parts appendix, colon, caecum and rectum
6.  The anus  - This is the exit  point of the  alimentary canal. It is where waste products (faeces) are passed out of the body.

ALIMENTARY CANAL







1.Mouth
After ingestion, food is mechanically broken down (crushed into small particles), by the grinding and chewing action of teeth. These increase surface area for the enzymatic activities and also make the food (small enough) suitable for swallowing through peristalsis movement. 

During chewing process food is mixed with saliva, which contains enzyme called salivary amylase or ptyalin. 

Function of chewing
i.It breaks down large pieces of food into small pieces for essay swallowing
ii.It mixes the food with saliva making the food slippery for easy swallowing
iii.It makes easy for digestive enzyme contained in small to penetrate the food.

Saliva
 is secreted by three different types of salivary glands ( contains) mucin) .These are.

Sub-lingual glands—beneath the tongue.

Sub –mandibula saliva glands—under the lower jaw.

Parotid salivary gland—in the cheeks in front of ears

Function of saliva.

1.    As solvent for dissolving food substances.

2.    Mucus lubricates the food for easy swallowing.

3.    Ptyalin digest starch to maltose.

4.    Dissolves chemicals taken into the mouth.

5.    Moistens the tongue, mouth and lips’; this enables person to talk.

6.    Reduce mouth acid, hence prevents tooth decay.

7.    Enables food molecules to reach the taste buds in tongue.

Tongue

It rolls the food into round masses (boluses) and pushes them down the oesophagus. The epiglottis prevents food from entering the trachea (windpipe). Tongue enables to speak.

Teeth

Teeth are for chewing and grinding. The dentition of each animal is highly adapted to its diet. Dentition refers to the shape, type, arrangement and specialisation of teeth in an animal.

Vertebrates have teeth that can be grouped into two categories.

-Homodont teeth.

-Heterodont teeth.

  

1. Homodont teeth, these are teeth, which have the same shape, size and functions.

Are in:-(a) Fish, (b) amphibians, (c) reptiles.

2. Hoterodont teeth; these are teeth which have different shape size and function. Are found in mammals.

Milk and permanent teeth.

Most mammals develop two sets of teeth during their lifetime. The first set to appear is called milk teeth or deciduous teeth. These are shed later in life and replaced by permanent teeth. Human milk teeth begin around five months of age. Around age of six most have 24 teeth. Four of these remain permanently. The other 20 are shed and replaced by a permanent set.8 other permanent teeth develop to make total of 32. The 4 molars at the back of mouth appear at about age of 18 and are called wisdom teeth.

DIAGRAMS.   Types Of Heterodont Teeth.

Types of teeth

1.    Incisors.

- Long and chisel shaped in front of mouth

-Used for cutting and  bite

- Adults has eight incisors. four in each jaw.

2.    Canine.

-Sharp and pointed

-Absent in herbivorous, the empty set is called diastema.

-Used for tearing. and grip food

-adult has four canines, Two in each jaw

3. Premolar

-       Blunt with ridges.

-       Have two cusps.

-       Used for crushing. and help canines in gripping  and assist molar for with grinding

- Adult has eighty , four in each jaw.

4. Molar.

-Like premolars, blunt with more ridges

-       to increase surface area for grinding and crushing

-       Have 3-4 cusps.

-       Used for  pound,grinding and crushing.,food so that it can be swallowed

-Adults have twelve molar.Six in each jaw 

Parts of the tooth and their functions.

Enamel- hardest non-living part containing calcium.

 - Is protective part also for biting and grinding.

Dentine- living cells, for replacing dead cells of the enamel.

Pulp cavity- inside the dentine; contain nerve endings and blood capillaries.

Blood capillaries- provides nutrients for the living tissue and removes waste products.

Nerve endings; detects heat, cold and pain.

Cement-fixes the tooth to the jawbone.

Diagram Main Parts Of The Tooth: incisor and Molar

       

 

1. Crown; part above the gum.

2. Neck; at the same level with the gum. It connects the crown and the root.

3. Root; part below the gum.

Dental Formulae.

Show the type, number, and position of the teeth in each half of the jaw i.e. it represents half the total teeth in upper and lower jaw.

1. Omnivorous; man   I  2    C  1   Pm  2   M  3    =32.

                                       2         1          2         3

                          

                          Pig   I 3       C1   Pm 4        M 3  =44.

                                    3          1         4             3

2. Herbivores; sheep I 0   C 0  Pm   3     M3         =   32

                                    3       1          3        3

3. Carnivores Dog  I 3    C 1    Pm4     M2 =42.

                                 3        1          4       3

1.      Dental caries; tooth decay and is most common.

Cause; -lack of hard food

            -Too much sugar food.

-    Lack of calcium and low level of fluoride in drinking water.

-    Lack of vitamin   D

-    Lack of proper cleaning of teeth.

Symptoms.

-          Noticeable when one eats sweet foods or drinks hot or cold drinks, i.e. pain.

Treatment – disease is halted by filling

-          If it reaches pulp cavity, only treatment is extraction of the tooth.

NOTE: very high content of fluoride in drinking water causes browning of teeth called dental fluorosis.

2.      Periodontal disease; affects the gum. The gums become soft and flabby i.e. does not support the teeth.

Cause- dental plague-bacteria

  -Lack of vitamin A and C.

   -Imperfect cleaning.

 -Too much sugary foods.

Symptoms.

-   Bleeding gum especially when brushing.

-   Gums become swollen, reddened, soft, and flabby.

-    If not treated; leads to loosening and eventually loss of teeth.

Treatment /control- proper care of your mouth.

 -Balanced diet especially vitamin A and C.

Rules to maintain teeth in a Health State.

1.      Regular cleaning and brushing especially after meals using tooth brush or tooth stick.

2.      Avoid too much food containing refined sugars like sweets, ice creams, and chocolates.

3.      Regularly eat tough fibrous food like sugar canes, carrots, fruits, vegetables, and nuts, maize (this helps to exercise teeth)

4.      Eat diet rich in vitamin C and A, i.e. citrus fruits, vegetables and calcium rich food, i.e. milk.

5.      Areas with low fluoride content in water, add fluoride to drinking water and use fluoridated tooth paste (this help to control decay).

Consult dentist regularly, at least once year, i.e. small cavities and tooth decay can be detected and treated easily

Starch+H₂O   ptyalin        Maltose.
2.Oesophagus
is a muscular tube that conveys food boluses from the pharynx to the stomach

This is a muscular tube composed of the circular and longitudinal muscles which are covered by layers containing the blood vessels and cells producing mucus.
•      The function of oesophagus is to pass food by contraction of the muscles, resulting into downward movement of food known as peristalsis.
The wall of oesophagus has circular and londitudinal muscles
     Peristalsis:  is the wavelike motion of food in the oesophagus caused by muscular contraction.
The wall of oesophagus has circular and longitudinal muscles..As the food is swallowed muscles above the bolus contract and longitudinal muscles relax pushing the bolus downwards HenceMovement of food down is not influenced by force of gravity.This explain why it is possible for a person to eat while standing on their heador lying horizontally

Fig.Peristalysis

At the junction between  the oesophagus and stomach is a ring of muscle called the Cardiac sphincter.When food reaches this point the muscles automatically relax and allow the food to enter into the stomach.And prevent the food the movement of food backinto the oesophagus

3.  Stomach

     This is  highly elastic muscular bag consisting of longitudinal and circular oblique submucosa muscles
At the lower end of the stomach there is group of sphincter muscles called the Pyloric sphincter. The contraction of this muscles closes entrance of food int duednum

Contraction and relaxation of the stomach muscles brings about churning, i.e. mixes content of the stomach.

The stomach

Gastric glands in the stomach wall produces gastric juices, which contain;

-Hydrochloric acid from parietal cells.

-Enzymes rennin, and pepsin from peptic cells.

-Mucus from goblet cells.

1. Hydrochloric acid HCL.

-Provide suitable acid medium for the enzymes to work best.

-Hydrolyses (breaks down) complex sugar into simple sugar.

-Kills the bacteria present in the food.

Unfolds proteins enabling pepsin to act on them.

Activates pepsinogen to pepsin.

2.  Pepsinogen . an inactive foem of Pepsin.

-Breaks proteins into polypeptides.

Why pepsin can not digest the proteins of cells producing it. Because is produced in an inactive form called pepsinogen. Which has to be activated by HCL. Also presence of mucus.

3.Rennin.

Coagulates (solidifies) soluble milk protein (casein) which is then acted on by pepsin.

Young mammals mostly produce the enzyme during suckling period 

.4. Mucus.

  Helps to lubricate food.

Prevents stomach lining from being digested by pepsin.

Prevents stomach lining from being corroded or eroded by HCL.

5. Water. Which provides a medium for enzyme  activity

1.Heat Burn

.Occasionally after heavy meal pressure in the stomach causes some HCL to leak in the oesophagus. The HCL will cause burning affect producing pain (heatburn) because there is no mucus in the oesophagus.

The stomach have circular and longtidunal muscles which contract and relax and in the process mix the food into a semi-liquid substance called Chyme

- Chyme is acidic due to the hydrochloric acid present in gastric acid

The main function of the stomach is:-•     Storage of food- for enzymes to act on it

•         Mechanical breakdown of food during chuming process.
•         Mixing the food with gastric juice by muscular action.
•         Secreting the enzymes pepsin that starts digestion of protein.
•         Curdling (coagulation) milk with the enzyme renin
•         Absorbing some simple chemicals such as water, salts in form of ions and alcohol
•         Producing  hydrochloric acid digestive glands
•         Preventing the corrosion of the stomach wall by hydrochloric and providing smooth movement of food materials.
•          The   stomach wall absorbs vitamins, water and drugs such as alcohol
•         The stomach’s pyloric sphincter allows small quantities of chyme to enter the duodenum at a time.
4.Small Intestine
The wall of the small intestine is less folded than the stomach. 
Most digestion takes place in the small intestine. It is a long coiled tube of about 4 -5 metres long. Is divided onto two regions i.e. duodenum and ileum.

Absorption of digested food takes place through the villi

.

i Digestion In The Duodenum.
Duodenum is the first part of the small intestine. .When the chyme chyme enters the duodenum, it stimulates  pancreas the pancreatic juices. other organ associated are

i.     Liver.

Secretes bile which is stored in the gall bladder and released through the bile duct.

Bile is a yellow-greenish pigment which contain bile salts.

Function of the bile.

-Breaks down fats/lipids into tiny droplets to increase surface area for enzymatic activities. This process is known as emulsification.

-Provide alkaline medium, for enzymes in the duodenum work best in alkaline medium.

-It neutralises the acidic chyme from the stomach.

-Aid digestion of  fat, by break down into tiny drplets(Emulsification),which increase the sufarce area upon which the fat-digesting enzyme act

ii          The pancreas.

 Secretes pancreatic juices which contain enzymes like

1.      Pancreatic amylase: breaks down the remaining starch in to maltose.

2.      Pancreatic lipase: digests fat droplets into fatty acid and glycerol.

3.      Trypsin: digests proteins into peptides

4.      Carboxypeptidase: digest peptides into amino acids.

5.   Sodium hydrogen carbonate (NaHCO₃) Neutralises acidity of chyme from the stomach, to provide alkaline medium for pancreatic enzymes to work best.

 ii.Digestion in the ileum.

Ileum is the second part of small intestine and longer section of the alimentary canal. The intestinal walls have intestinal glands (cells) which secrete mucus and alkaline fluids known as Intestinal juice (succus entericus) which contain the following enzymes.

1.      Erepsin (peptidase), this digest peptides to amino acids, i.e. simplest form of protein.

2.      Maltase, digest maltose to glucose, i.e. simplest form of carbohydrates.

3.      Lipase, digest fat droplets to fatty acids and glycerol, i.e. the simplest form of lipids.

4.      Sucrase, digest sucrose to glucose and fructose.

5.      Lactase, digest lactose to glucose and galactose.

Absorption

Is the process by which the soluble end products of digestion (like glucose, amino acids, fatty acids and glycerol) diffuse into the blood stream. Mainly absorption takes place in the small intestine. How ever absorption of alcohol, some water, soluble vitamins like B and C, and soluble salts takes place in the stomach.

In the large intestine, vitamins K and B₁₂ are synthesised by bacteria and protozoa also absorption of water takes place here.

Assimilation (fate of absorbed food)
Some are stored in the liver and then released in accordance with the body needs. Example, vitamins A, D and B12, minerals like iron, copper, potassium and calcium

Assimilation is the process by which the end products of digestion are incorporated into the cell metabolism. Most of the absorbed nutrients are first carried by Hepatic portal vein to the liver. The liver regulates the concentration of nutrients in the general circulation. Assimilation is done as follows:-

1). Glucose;

-       Some used during respiration to give energy (ATP).

-       Some stored as glycogen in the liver and muscles.

-       Some converted and stored as fat beneath the skin (adipose tissue).

2). Amino acids;

-       Some used in synthesis of protein.

-       Some used in growth and repair of worn out cells.

-       In absence of glucose and fat, they may be used during respiration to give energy.

-       When in excess deamination takes place (removing the amino group)

3). Fatty acids and glycerol.

-       Oxidised to release energy during respiration.

-       Stored as an adipose tissue beneath the skin, which help to insulate the body.

-       Some are stored around the heart, kidney and other abdominal organs.

4). Vitamins and mineral elements.

Adaptation of ileum for the work of digestion

1.  It has secretory glands which produce digestive enzymes
2.   It is connected to the liver by the bile duct. The bile duct enables bile to reach the ileum
3. The ileum has mucus- secreting glands to ensure constant supply of 

Villus contain lacteal (a lymph vessel) for absorption of fatty acids and glycerolncrease the surface area for absorption of food.


Adaptation of  ileum for absorption.
i.The lining of the ileum has finger-like projection called villi..these structures increase the surface area for the absorption of food
ii.The ileum is very long(about six metre).It therefore has large surface area for absorption of soluble products of digestion
iii.The villi have large network of blood capillaries.These transport absorbed food in all parts of the body
iv.The inner lining of ileum is folded. This  increases the surface area that is in contact with food.
v.The lining of  the ileum is only one cell thick.Thus the digested food difuses through a short distance into capillarie
The functions of the small intestine include:
•          It absorbs must of the small soluble food molecules produced in the digestion process.
•         It completes the digestion of carbohydrates ,proteins  and fats,
•         Neutralization of the acids from the stomach takes place in the small intestine.
6.Large intestine (Colon)

The large intestine comprises of the colon and the rectum. Its function is the absorption of water and the package of undigested food forming faeces. 

Occasional relaxation of sphincter muscles around the anus result to Egestion or defaecation.

    In the large intestine there is large number of bacteria and protozoa, there are micro organisms which help to synthesize vitamin K and B12 and riboflavin. Also these micro organisms lead to the formation of gases like carbon dioxide, methane and hydrogen sulphide, which are released through the anus.
They have no function in man. In herbivorous (cattle or sheep) the caecum and appendix contain bacteria that secrete enzymes called cellulase which digest cellulose to glucose.

In Non Ruminant Herbivores like horses, rabbits and rodents the micro-organisms are located in the caecum which digest cellulose to glucose.

Caecum And Appendix
They have no function in man. In herbivorous (cattle or sheep) the caecum and appendix contain bacteria that secrete enzymes called cellulase which digest cellulose to glucose.

In Non Ruminant Herbivores like horses, rabbits and rodents the micro-organisms are located in the caecum which digest cellulose to glucose.

Anus:

This is an opening in the alimentary canal which has a ring muscle sphincter which allows passage out of feaces.. 

Human digestive process

Elimentary canal	Enzymes secreted	Substance digested	Product of digestion
Mouth	Salivary gamliase(pytalin)	carbohydrates	Maltose
Stomach	Pepsin	Protein	Peptides
	Rennin	Soluble milk protein	Insoluble milk protein
Duodenum	Trypsin	Protein	Peptides
	Pancreatic amylase	Starch	maltose
	Pancreatic lipase	Lipids	Fatty acids and glycerol
Ileum	Maltase	Maltose	Glucose
	Sucrase	Sucrose	Glucose and  fructose
	Lactase	Lactose	Glucose and  galactose
	Peptidase	Peptides	Amino acids

Digestive system of other mammals
The ruminant digestive system
A ruminant is an animal that chews food, swallows it then returns it to the mouth later for further chewing. This is called chewing cud.
Examples of ruminants are cows, goats, sheep antelopes and giraffes.
The digestive system of a ruminant is different from that of a human being.
Ruminant have a more elaborate system to enable cellulose digestion. 
The stomach of ruminant has four chambers: 
i.Rumen, 
iiReticulum, 
iiiOmasum, iv.
 Abomasum.

Ruminant chamber

1.Rumen
 is the part when first chews and swallows a mouthful of plant matter the food enters
-Bacteria in the rumen immediately  start digestiing the celluolse present in the plant materials.
- Chewing cud softens and helps break down plant fbres making the more accessible to digestion of bacteria.
- food is coarse and green
-The food is regurgitated and chewed again
2.Reticulum
The reticulum has honeycomb appearance
-food materials is mixed thoroughly with water
- The food is less coarse,more watery, less green and very smelly compared to the food in the rumen
3. Omasum
Has broad longitudinal folds like the leaves of a book
- these folds help to remove water from the food
-Food is in formof fine paticles and has very little water

4. Abomasum
is the ruminant's true stomach
-has gastric acid that facilitaes the digestion of protein
- It kills microorganism that may have spilled over from the rumen

Non Ruminant Herbivores

-    Have only one chamber of stomach, which does not contain cellulose-digesting microorganisms.

-     In horses, rabbits and rodents the microorganisms are located in the caecum which acts as rumen in ruminants. In the horse absorption takes place in the colon.

The main differences between the ruminant digestive system are:
a.The ruminant digestive system has four stomach chambers. Human beings have one stomach  chamber
b.  Ruminants have no upper   incisors and canines instead. They have a hormy pud. The pad helps in the chewing of food.
They also have a gap on the lower jaw called diastema Humans have upper incisors and no diastema.
c.Ruminants chew cud.  They regurgitate what they had swallowed and chew it again. Human beings do not chew cud.
d.The ruminant’s digestive system has micro-organism that help to digest fibre and synthesize vitamin B. Human beings cannot digest fibre.
Disorders and diseases of the digestive system
These include diseases and disorders that affect the teeth, the oesophagus, the stomach and the small and large intestines.
Examples:
•          Dental carries
•         Heart burn
•          Stomach ulcers
•         Constipation
•         Flatulence

1.Dental caries
This is the dental disease in which the teeth decay
The decay is caused by acids produces by the action of bacteria on sugary food left between the teeth.
There are always bacteria present in the mouth 
The bacteria combine with acid, saliva and remains of food to form plaque.
Plaque is the sticky substance often found between teeth.
Plaque begins to form within 20 minutes after we eat. The acid dissolved the enamel in the tooth forming a cavity. If this cavity is not treated it reaches the pulp cavity and  nerve endings inside the teeth  causing an infection.
Signs and symptoms of dental caries
•         Toothache especially after eating sweet cold or hot in the foods.
•         Holes in the teeth
Control measures for dental caries
•         We should brush our teeth and  floss frequently in order to remove plaque
•          Damaged teeth can be filled or covered with an artificial crown or pulled out.
•         Minimize intake of sugary foods.
•         Visit a dentist  regularly for dental check-ups
2.Heartburn
Heartburn is a burning or painful sensation in the oesophagus. It is caused by regurgitation of the stomach contents. The hydrochloric acid in the stomach makes these contents acidic and irritating to the oesophagus.
The stomach contents flow back into the oesophagus due to the following:-
•         Certain foods such as pepper, citrus fruits, very cold or very hot foods, spiced foods and carbonated fruits.
•         Drugs such as alcohol, caffeine (from tea coffee or cola), cocaine and tobacco.
•         Lying down or bending over soon after eating
•         Pressure   on the stomach due to pregnancy, obesity, tight clothing  or strenuous activity.
•          stress
Signs and symptoms of heartburn
•         A burning feeding in the  chest or throat
•         A sour taste in the stomach
•         Difficult swallowing
•         Hoarseness  or loss  of voice
Prevention and treatment of heartburn
•         Avoid food that cause  heartburn
•         Avoid alcohol, caffeine, tobacco and recreational drugs
•          Obese should lose weight
•         Avoid  very hot or very cold foods
•         Antacids help to reduce acidity
•         Drinking water helps to dilute the acid in the stomach
•         Do not eat a large meal just before going to bed or taking part in strenuous exercise
•         If the heatburn gets worse especially at night when lying flat, try sleeping with the upper body somehow raised.
•         Milk helps to reduce the strength of the acid causing   heartburn.
3.Stomach ulcers
A stomach ulcer is a sore in the stomach lining or small intestine which is caused by the erosion of the stomach’s mucus coating, exposing the stomach to the action of digestive enzymes and acids
TYPES OF ULCERS
•         Peptic ulcers
•         Duodenal ulcers
Peptic ulcers are found in the stomach
Duodenal ulcers are found in the duodenum.
The mucus can be eroded by
•         Bacteria called Helicobacter pylori
•         Certain  medication like aspirin
•         Smoking, alcohol and caffeine
*Emotional stress is known to worsen stomach ulcers.
Signs and symptoms of stomach ulcers
•          Burning pain  in the stomach
•         Nausea and  vomiting
•         Tiredness and weakness
•         Blood in vomit and stool.
Constipation
This is a condition whereby one unable to remove the undigested food materials form the bowels through the anus. It occurs when the stool becomes dry and hard due to excessive absorption of water in the colon
Causes:
•         Inadequate of amount  of fibre in the diet
•         Inadequate intake of liquids
•         Lack  of exercise
•         Abuse of laxatives. Laxatives are drugs that help to loosen the bowels by softening the stool and increasing the amount of water in the colon.
Signs  and control of constipation
•         Eat enough fibre
•         Drink plenty of liquids every day
•         Go for a long call when you feel the urge to.
•         Seek medical help if constipation is persistent.

4.Flatulence
This is an uncomfortable feeling caused by too much gas in the stomach.
Causes
•         Swallowed air
•         Eating food that produce  gas for example beans, cabbage, onions, milk and bread
•         Eating meals that have too much fat lead to a production of large amounts of carbon dioxide when the fat is neutralized in the small intestine.
•         Poor absorption of carbohydrates in the gut
Signs and symptoms of flatulence
•         Abdominal pain
•          The constant urge to pass wind
•         Bloating (an accumulating of gas in the stomach).
Prevention and control of flatulence
•         Avoid foods that produce gas or eat them in moderation
•         Avoid lying down after eating because it makes it easy for gas to pass from the stomach into the intestine.
•         Chew food carefully to assist in proper digestion of carbohydrates.
•         Limit the amount of lipids in the diet.

NUTRITION IN PLANTS
Mineral requirements in plants.
Plants are autotrophs, they make their own foods however, and they also need obtain chemical elements from the environment in order to make the food.
The elements are divided into two group’s,. non mineral and mineral elements.
Non- mineral elements are carbon, Hydrogen and oxygen. The mentioned elements are found in water and in the air.
Mineral Elements
Mineral elements are found in the soil dissolved in water. They are absorbed through plant roots
They are divided into two major groups:
Macroelements and Microelements.

Macroelements are needed by the plants in relatively large amounts: They include.

ELEMENT	SOURCE/ROLE	DEFICIENCY SYMPTOMS
Nitrogen (N)	Protein synthesis, manufacture of chlorophyll; promotes normal plant growth  It is obtain from commercial fertilizers and from their Rhizobium bacteria in the roots of leguminous plant fix nitrogen from the air for use by the plants.	Leaves become pale green or yellow; small leaves, thin weak stems, stunted growth.
Phosphorous (P)	-  it is obtained from bone meal and phosphate fertilizers -  It promotes root and branch growth, protein synthesis and energy release in respiration.	-  Poor growth of roots leaves and branches leaves become reddish purple
Potassium (K)	-  it is obtained  from soil minerals organic material and commercial fertilizers -  It is used during photosynthesis and protein metabolism in younger leaves	-  Yellow leaves with dead spots especially at the margins and tips.
Magnesium (Mg)	It is obtained from the soil minerals, organic  material (such as composit), commercial fertilizers and lime manufacture of chlorophyll aids enzyme activity	Yellowing of leaves       (Chlorosis)
Calcium (Ca)	It is obtained from lime gypsum and commercial fertilizers       It promotes normal growth of plant and cell wall formation.	Poor root growth death of growing regions
Sulphur (S)	-  It is obtained from rain water, gypsum  and commercial fertilizers	-  Stunted growth  and yellow patches on leaves
Iron (Fe)	Aids chlorophyll formation      Important in transportation of oxygen	Thin, weak systems. Leaves become white or pale.

Micro elements 
are mineral elements that are needed for growth and survival but only in small quantities

Microelement	functions	Signs of deficiency	effects of excess
Boron	Aids in wwater intake by cells	Discolourde leaves	Scorched leaves
Copper	Ads in  in the production of protein	Wilting	Scorched leaf edged
Iron	in formation of chrolophyll	Yellowing of leave	Brown sport on leaves
		between veins
Manganese	catalyst for enzymes action	White specks leaves	iron deficiency
Zinz	Regulation of plants growth	purple	pale green

Photosynthesis
•          Photosynthesis is the process which green plants, some bacteria and some protoctista make food using water, carbon dioxide and energy from the sun.

In green leaves in sunlight two opposite processes are going on at the same time, i.e. photosynthesis and respiration. Respiration is breaking down what photosynthesis has build up. The two processes are linked because they make the sun energy available per use both of plants and animals.

Difference between photosynthesis and respiration.

Photosynthesis. 1. Raw materials-CO2 & H2O. 2. Oxygen is given out.. 3. Build carbohydrates. 4. Energy is stored. 5. Much faster than respiration. 6. In the presence of sunlight only. 7. Goes in green plants only. 8. Takes place in the chlorophyll

Respiration. 1. End product (waste) material CO2 & H2O. 2.Oxygen is taken in 3. Carbohydrates are used up. 4. Energy is set free. 5. Slower than photosynthesis. 6. Goes on all the time –day and night. 7. Goes in all living organisms. 8. Takes place in the mitochondria

The process takes place in cellular structures called chloroplasts.  Organisms that photosynthesis are called primary producers because they are the source of food for all the other organisms
The synthesis of sugars in photosynthesis is usually summarized by the following equation




The importance of photosynthesis:
•          Photosynthesis produces food for the plants. Some animal’s feeed on plants in order to live.  Other animals feed on the plant- eaters. Hence photosynthesis is important for the lives of plants as well as animals.
•         Photosynthesis produced oxygen
This helps to replace oxygen that has been used during burning, respiration, rusting and other processes
•           The process of photosynthesis also uses the carbondioxide from the atmosphere. Carbondioxide is a byproduct of respiration and is harmful if excessive amount accumulate in the atmosphere.
•         Photosynthesis converts light energy from the sun into chemical energy.
The energy produced is used by plants and animals. Animal obtain energy by eating plants or eating animals that eat plants.
•          During photosynthesis some plants produce extra amounts of food which they store in storage organs. The storage food is used when conditions do not allow the synthesis of adequate amounts of food.

The leaf is the main site of photosynthesis in plants
The structure of the leaf in relation to photosynthesis
The leaf  has two structures
•          External structures
•         Internal structure

External Structure of leaf

Fig. external of leaf

Petiole or leaf stalk: Attaches the leaf to the branch or stem. It is keep the lamina in a position that will enable it to get maximum amounts of sunlight.

The lamina :  Has a large surface area. This maximizes the absorption of sunlight and carbon dioxide. It has thin so that carbon dioxide and sunlight diffuse over a short   distance to reach cells.

The midrib and veins- Contain xylem and phloem xylems vessels transport water  and  mineral salts to the leaf.
Phloem vessels transport manufactured food to other part of the plants
The internal structure of a leaf.

Fig The internal structure of leaf

1.The cuticleThis is a transparent layer on the leaf. It allows light to penetrate to the photosynthetic cells
The cuticle protect the leaf from injury, pests and excessive loss of moisture.
There is no cuticle over the stomata in order to allow gaseous exchange.

2. The epidermis:
This is a layer that is one cell thick. It is the outermost layer of cells found both on the lower and upper surface of leaf.
It allows sunlight to penetrate the leaf easily.
The epidemic has pores called stomata. Stomata are surrounded by guard cells which close and open the pore. The guard cells also have chlorophyll so they can photosynthesize.

3.Mesophyll – This is made up of the palisade layer and the spongy layer. Mesophyll enables the cells to absorb maximum amounts of sunlight. Palisade cells also have many chloroplasts where photosynthesis takes place.
The spaces between the cells allow gaseous exchange.

Fig.  Cross section of leaf to show mesophyll

4.Vascular Bundles
These are xylem and phloem tissues which serve as conducting tissues.
Xylem- Transport water and mineral salts
Phloem- Transport manufactured food.

The process of photosynthesis
Photosynthesis takes place inside cell organelles known as chloroplasts
Photosynthesis takes place in two stages.  
1.The light stage
2.The dark stage
1.The light stage
This stage takes place in the grana of the chloroplast
The grana contain chlorophyll. Chlorophyll molecule absorbs light energy from the sun.
The light energy sets off reactions that lead to formation of energy that is stored in a chemical compound called ATP) adenosine triphosphate). This energy is used in the dark stage of photosynthesis.
Light energy causes photosynthesis where by water molecules (H₂O) are split into hydrogen ions (H⁺) and oxygen ions (^O2-)

Photolysis  is the process whereby water molecules are split into hydrogen ion and oxygen ion
H2O light 2H⁺ + O^2-
          Energy             
-Some oxygen is released into the atmosphere the rest is used for respiration in the plant
-  Hydrogen is used in the dark stage.

The dark stage:
•          This stage does not need light
It takes place in the stoma. The stoma is a colourless matrix of fine material.
•          During the dark stage, hydrogen ions (from the light stage) and the Co₂ from the atmosphere absorbed through the stomata combine to form glucose the simplest carbohydrates. The  glucose is later converted to starch at night
•         Starch is insoluble and acts as temporary store of excess carbohydrates.
Glucose may also be converted to cellulose (The structural material of plants).

Environmental Factors and the rate of photosynthesis.
Several environmental factors have profound effect on the rate of photosynthesis. These are:-
•         Carbondioxide concentration:
The increase of CO₂ concentration in the atmosphere leads to the increase in the rate of photosynthesis when other factors like light intensity and temperature are at their optimum level. However if the concentration of carbondioxide increases It damages the plants.

Effects of carbon dioxide concentration on the rate of photosynthesis
  Light intensity and light quality: (wave length)
Light provides the energy required to drive the process of photosynthesis
Starting from a low intensity, the rate of photosynthesis increases as intensity increases.
 At very high  light intensities, chlorophyll is damaged and the rate of photosynthesis falls

Chlorophyll absorbs light mainly in the blue and red wavelengths and these are the ones used for photosynthesis.
Temperature
  The reactions of photosynthesis are catalyzed by enzymes.
The rate of photosynthesis increases as the temperature increase. It doubles at 10⁰C  but beyond 40⁰C the temperature  denatures the enzyme and rate of photosynthesis will be lowered 
Effect of temperature on the rate of photosynthesis
•          Water availability:
•         Water is one of the raw materials of photosynthesis. If plant lack water it will dry up.
Availability of mineral salts:
Nitrogen and magnesium are important constituents of chlorophyll. Plants grown in oil deficient of nitrogen and magnesium produce little chlorophyll
.
UNDERGROUND STORAGE
Are organ formed  from modified stem,leaves or roots
-There are relatively large and fresh. These are
1.Bulb

an onion bulb

A bulb is an underground storage organ formed from plants stem and leaves.Example onion



2. Tuber
Is a freshy storageorgan formed from either a stem or root.
a. stem tubers.is formed at the end of underground stem. Eg. Irish potato,Sweet potato,and cassava

Fig Irish potato

b.Root tuber.are solely as food storage organs are more or less permanently replenish their reserve

3. Corm 
Is underground storage organ formed from the plant stem.Examples areYams. Cocoyams andCrosuse

Fig Cocoyam

4. Rhizome
is a a swollen stem, bearing leaves and roots which grows horizontally on the surfaceor just below the surface.Example Ginger

Fig Ginger

Food Processing, preservation and storage
Food processing  refers to all the ways in which food is treated in order to make it edible, appetizing and safe to eat or to keep it fresh for long time.

Food processing techniques
i. removing unwanted outer layers,Example peeling potatoes
ii liquefaction. e.g producing juice by squeezing fruits
iii.Chopping or slicing. E.g Banans, mangoes and cassava
iv.Fermentation. eg making wine from banana and grapes
v.cooking e.g boiling, broiling ,frying, steaming.
vi. deep frying
vii. Baking

Food preservation refers  all specifically to the methods of food processing that are used to prevent food from spoiling or going bad.
Food is preserved because it can be produced only at one season. It needs to be stored produce only available for future use. Sometimes food may be produced in one area and then transparent to be consumed somewhere else. Food storage refers the method used to keep reserves of food for future use.
 these method includes
1. Canning or bottling- for getting rid of microorganism
2. pasteurization and boiling.-using high temperatures to kill microorganisms that causes spoilage
4.Refrigeration- using very low temperatures to slow down the growth of microorganism

5 irradiation which involves using radiation, e.g gamma ray
6 drying, salting, applying honey or smoking- eliminating the moisture that needed for growth of microorganism
7. Adding chemicals such as salt, sugar and carbon monoxide prevent physical changes in food

Methods of food preservation:
There are two major methods of food preservation There are:-
Traditional methods
Modem methods
Traditional methods include
•          Curing
•         Drying in the sun
•         Smoking
•         Cooking
•         Storage in granaries and pits
•         Curing
i.Curing involves the addition of substances such salt, sugar, spices and vinegar to animal foods, most meat and fish curing binds or removes water making it unavailable for the growth of microorganisms.
Eg.Sausages, bacon and corned beef.

  Drying  in the sun
This   method is used to preserve rice, maize, cloves, bananas, peas, lentils, meat, fish, cassava and green leafy vegetables.
The food is left in the sun to remove reduce its moisture content. Reducing the amount of water in the food discourages the growth of microorganisms.
Smoking
Smoking reduces the moisture content of food to prevent growth of micro-organisms. Grains, meat and fish can be dried slowly over a smoking wood fire,
  Cooking  
these methods of cooking are simple and include boiling, steaming, baking in hot ash and roasting.  This processes help to soften food improve flavour or preserve food. For example potatoes, bananas and maize can be boiled before being dried.
•          Storage in granaries and pits
•         Dry grains are stored in granaries which are usually raised above the ground. The granaries keep grain safe from insects, rodents and birds Harvested yams, potatoes and cassava  can be  stored in large pits in the ground after drying. 
   Salting
Is the addition of salt to food.Salt remove water from the food and kill micro-organism that would otherwise spoil the food.example meat, sardines and fish
Fermentaion. 
is the conversion of carbohydrates such as sugar into acid aor alcohol.Example milk

Advantages of Traditional methods of food processing, preservation and storage
•         They are simple and can be done by most people
•         They use locally available materials and simple technology, thus keeping costs low.
•         No harmful chemicals are added to the food
•         Curing and smoking add a distinct flavour to the food.
•          Most methods do not destroy nutrients
•         Can be applied in rural areas where no services such as electricity
Disadvantages of Traditional methods of food processing, prevention and storage
•         Food can be preserved and stored for only limited periods  of time
•         Traditional methods are manual and thus difficult to do on a large scale
•         Traditional methods are highly limited in the variety of foods that can be processed, preserved and stored.
Modern methods of food processing, preservation and storage.
•         Refrigeration and Freezing
Refregation is the temporary storage of food at low temperatures of up to 4 centigrade in order to slow down the growth of micro-organism.
Freezing involves storing food at very low temperature (below-10⁰C) in order to stop the growth of microorganism.
Foods that can be refrigerated include milk, fresh fruit and vegetables, juice and butter freezing is mostly used for meat, fish, fruits and vegetable.
•          Pasteurization
This method of preservation was named after its inventor, Louis Pasteur.
It involves heating food to very high temperature for a short time in order to kill microorganism that can spoil the food.
Examples of foods that can be pasteurized are milk and fruit juice
·     Canning and bottling
In this methods food is preserved by heating it in airtight vacuum- sealed bottles or cans. The countainer is filled with food then the air is pumped out to form a vacuum.
The container is sealed and heated to kill microorganism and enzymes, but not enough to overcook the food.
Examples of the foods that can be bottled or canned are tomatoes, fruits and fruit –juice beef, fish and baked beams.
•    Using additives
Chemicals such as sodium benzoate, sodium chloride and vinegar are added to food to slow down the growth of microorganism. This is commonly done to preserve fish and meat
•     Drying ( Dehydration)
Food is dried using either hot blast of air from a vacuum dryer
After drying the food is then sealed in moisture- proof containers.
•    Irradiation
Irradiation uses rays of energy to stop growth of microorganism in stored food stuffs.
This makes foods last longer
Eg onions, beans and potatoes.

FOOD STORAGE
Refers to the methods used to keep reserves of food for futures

Traditional methods of food storage
1. Storage in granaries and pits
Dry grains are stored in granaries which are usually raised above the ground


2.Storage in pots and pits
processed food such as flour, dried vegetable and cassava are stored

Advantages of modem methods of food processing, preservation and storage.
•         Food can last for many months or even  year
•         Modern methods can process, preserve and store a large a large variety of food
•         The advanced technology
Disadvantages of modern methods of food processing, preservation and storage.
•         The chemical used can be harmful if eaten in excess
•         The processes used for example irradiation canning and pasteurizing, require special skills.
•         Sometimes nutrients are lost thus lowering the nutritional value of food.

The importance of food processing, preservation and storage
•         Prevents wastage of food.
•         Saves money by preventing  spoilage of food
•         Maintains the quality of food
•         Prevents the growth of microorganism that can cause illness.
•         Improves the flavour of food.
•         Removes harmful toxins and microorganism
•         Makes foods available even when they are not in season.
•         Enables transportation of delicate and perishable food such as milk and fruit over long distances.