Animals generally cannot manufacture their food. Rather, they depend directly or indirectly on plants for their food. Hence they are called heterotrophs. Based on their food types, animals are grouped into three:
- Carnivores which feed on flesh or other animals e.g. lion.
- Herbivores which feed on plants e.g goat.
- Omnivores, which feed on both plants and animals e.g man.
CLASSES OF FOOD SUBTANNCES
Foods eaten by animals are generally classified into seven i. e.
- Fat and oil
- Mineral Salt
This is got from food like bread, yam rice etc. It basically consists of carbon, hydrogen and oxygen. Carbohydrates are of three types:
- Monosaccharides (Simple sugars) which include glucose, fructose and galactose
- Disaccharides (Reducing sugars) which include maltose, sucrose and lactose.
- Polysaccharides (Complex sugars) e.g starch, cellulose, chitin under the action of enzymes like ptyalin, maltase, lactase etc, and starch yields glucose as product of its digestion. Excess carbohydrate is stored in the body in form of glycogen in muscles and liver. This can be reconverted to glucose during starvation.
Importance of Carbohydrates
- It gives animals energy.
- It provides heat needed to maintain body temperature
- It can be used for lubrication e.g mucus.
- It provides the body with a strong framework e.g. exoskeleton in insects.
These are complex molecules made up of smaller units called amino acids. Protein is made up of carbon, hydrogen, oxygen, nitrogen and sometimes phosphorus and sulphur. Food like egg, meat, fish, beans etc gives you protein. Proteins are broken down into amino acids under the action of enzymes like pepsin, rennin, trypsin and erepsin.
Importance of Proteins
- Growth in young ones.
- Repair of worn-out tissues.
- Production of enzymes.
- Production of hormones.
- It supports reproduction.
- It is for tissue and all formation i.e body building.
FATS & OIL (LIPIDS)
Fats are solid lipids at room temperature while oil is the liquid. Fat and oil consist of carbon, hydrogen and little oxygen. When digested, it gives rise to fatty acids and glycerol. Foods like palm oil, groundnut, Soya beans give fat and oil. Lipids are broken down to fatty acids and glycerol when acted upon by lipase enzymes.
Importance of Fat and Oil
- It gives you energy even more than carbohydrates
- It supplies essential fatty acids to the body.
- It helps in the maintenance of body temperature
- It provides the body with fat-soluble vitamins
These are usually taken in very small quantity in the food we eat except sodium chloride (table salt) and iron tablet, which can be taken directly by man. The lack of these salts results in nutritional deficiency. The minerals include calcium, magnesium, potassium, Phosphorus, sulphur, chlorine, iron, Iodine, fluorine, manganese, copper, cobalt and sodium.
Importance of Mineral Salts
- Regulate body metabolisms
- Components of bones and teeth
- Aids blood formation
- Control chemical reactions in the body
- Aids the formation of enzymes and pigment
These are organic food substances needed by man and other animals in small quantity for normal growth and development. Lack of or inadequate supply of any of these vitamins results in nutritional deficiency.
Vitamins can be grouped into two:
- Water-soluble vitamins
- Fat – soluble vitamins
The water-soluble vitamins include: vitamins B complex and vitamin C. Vitamin B complex include vitamin, B2, B3 , B5, B6 and B12
Fat-soluble vitamins include vitamins A, D, E and K.
VITAMINS, SOURCE FUNCTIONS AND DEFICIENCY SYMPTOMS
|Vitamin A||Liver, eggs, fish
milk, palm oil, fish Vegetables
|(i) Normal growth of
body cells and skin
(ii) Proper vision of the eye
|(i) Night blindness
(ii) Reduced resistance to disease
|Vitamin B1||Yeast, milk, beans,
|(i) Normal growth
(ii) Proper functioning of heart
and nervous system
|Beri-beri (wasting of
|Vitamin B2||Yeast, soya beans,
egg, milk, green
|(i) Growth, proper functioning
of the eye
(ii) Formation of co-enzymes
|(i) Slow growth
|Vitamin B3||Yeast, beans, milk,
|Formation of co-enzymes for cellular respiration||Pellagra|
|Vitamin B12||Kidney, liver, fish
|Formation of red blood
|Vitamin C||Fresh fruits and
|(i) Aids wound healing
(ii) Helps to resist infection
|Vitamin D||Fish, milk, egg,
|(i) Increases absorption
Of calcium and phosphorus.
(ii) Calcification and hardening Of bones
|Vitamin E||Green vegetables,
Egg, butter, liver
|Promotion of fertility
|Vitamin K||Fresh green vegetables, liver||Aids blood clotting||Hemorrhage|
This is of utmost importance to all organisms and it is made up of two elements, hydrogen and oxygen. Water can be got from food, river, stream, pond etc. water makes up 75% of the human body.
IMPORTANCE OF WATER
- Metabolic activities of the body of animals.
- Digestion of food.
- Maintenance of body temperature.
- It is a medium of transportation for all nutrients.
- It helps to maintain the osmotic balance in body tissues.
- It helps in excretion of metabolic waste from the body e.g urine.
These are indigestible fibrous materials got from vegetables, fruit, carbohydrates and proteins. Roughages aid digestion, lack of which can lead to constipation.
- State three importance of; A. Carbohydrate Protein C. Lipids.
- Mention five disease that may result from the deficiency of vitamins.
Balanced diet is a diet containing a correct proportion of all the food substances. On a general note, a balanced diet contains 15% protein, 15% fat and oil, 10% vitamin, minerals and water and 60% carbohydrate. Once a food is taken at these proportions, there is a normal growth and development in the body.
FUNCTIONS OF BALANCED DIET
- It makes us healthy.
- It gives ability to be resistant to diseases
- It makes available energy needed to carry out all biological activities.
- It prevents malnutrition and deficiency symptoms. For examples, a diet that lacks protein results into a nutritional disease called kwashiokor in children.
The protein deficient child has the following features
- Retarded growth.
- Loss of weight.
- Swollen legs effect (oedema).
- Cracked / split stomach and thin legs e.t.c.
- State two importance each of A. protein B. carbohydrates C. vitamins
- State three importance of balanced diet
Enzymes are organic (protein) catalysts produced by living cells which help to speed up and slow down the rate of chemical reactions. Digestive enzymes aid the breaking down of complex food substances into simple, soluble and diffusible form. Enzymes have the following characteristics.
- Enzymes are soluble
- Enzymes are protein
- They are specific in their actions
- Enzymes are sensitive to temperature i. e. they work best between 35oC to 40oC
- Enzymes are PH specific
- Enzymes brings about reversible reactions
- Enzymes needs co-enzymes to activate them and can be inactivated by inhibitors such as mercury and cyanide
CLASSES AND FUNCTIONS OF ENZYMES
Digestive enzymes are classified based on the type of food they act upon. These include
- Proteases e. g. pepsin, rennin, trypsin and erepsin. They act on protein.
- Amylases e. g. ptyalin, lactase, maltase, sucrose. They act on carbohydrates
- Lipases which act on lipids (fats and oils)
- What are enzymes?
- Outline five characteristics of enzymes
GENERAL EVALUATION/REVISIONAL QUESTIONS
- State two food items each that supply A. Protein B. Lipids C. Mineral salts
- List two functions each for protein and lipids.
- State the functions of A. Chlorine B. Magnesium C. Iodine.
- What are the diseases resulting from deficiency of: A. Sodium B. Calcium C. Iron
- State the functions and deficiency symptoms of all the water soluble vitamins
College Biology, chapter 6, page 95 – 103
- Vitamins are organic food substances required by animals in ____ quantity A. no B. small C. large D. high
- The following except one are fat-soluble vitamins vitamin A B. Vitamin B C. Vitamin K D. Vitamin E
- One of the following food substances is indigestible in man A. protein B. lipids
- roughages D. carbohydrates
- The highest source of energy is from _______ A. carbohydrate B. proteins C. lipids vitamins
- Rickets (poor bone formation) in children is a deficiency symptom of ____ A. potassium B. calcium C. chlorine D. manganese.
- Make a table of food tests showing the column of food, the test, observation & inference.
- Make a table of important mineral elements in animals, their functions and deficiency symptoms
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