NUTRITION (PROTEIN, CARBOHYDRATES, LIPIDS, VITAMINS, MINERALS)

NUTRITION

All animals are heterotrophs and require food from the environment. 

If the food of a number of different animals is broken

down we find that it consists.

1. proteins 

2. carbohydrates

3. fats

4. water

5. minerals

6. vitamins

All animals require the above-mentioned broad categories of nutrients although in different amounts. Some of these nutrients are used mainly as fuel. 

• carbohydrates

• fats

While others are required principally as structural and functional components.

• proteins

• minerals

• vitamins

1. PROTEIN

Proteins are continually synthesised in the cells as they are the principal component required for growth. Proteins are composed of amino acids which are derived largely from the diet and partly from the breakdown of protein available in the body.

All proteins are made from about 20 different amino acids in various y combinations.

•Non-essential amino acids

The amino acids that are synthesised in the body are called non-essential amino acid.

1.Glycine

2.Alanine

3.Serine

4.Tyrosine

5.Aspartate

6.Glutamate

7.Proline

8.Hydroxyproline

9.Citrulline

10.Histidine

11.Arginine

• Essential amino acids

The amino acids that have to be supplied through diet are known as essential amino acids.

1.Phenylalanine

2.Lysine

3.Isoleucine

4.Leucine

5.Valine

6.Methionine

7.Cystine

8.Tryptophan

9.Theronine

2. CARBOHYDRATES

Fifty five to seventy per cent of the required energy in animals is derived from carbohydrates. However, fats and proteins can also be broken down and used for supplying energy.

Most animals use a variety of hexose sugars like glucose, fructose, mannose, and galactose as interchangeable sources of energy.

3. LIPIDS (FATS)

All animal tissues contain lipids or fats as essential components of cell membrane. It is also stored in certain tissues. Lipids are body's chief source of energy and are essential for diverse functions such as insulation, padding, synthesis of steroid hormones and carriers of fat soluble vitamins.

4. VITAMINS

Animals cannot sustain a healthy life if they are fed on a diet having only carbohydrates, fats and proteins. They also require vitamins in small quantities in the range of milligrams or micrograms. These function as coenzymes in metabolic reactions.

• LIST OF VITAMINS

 *Lipid-soluble vitamins

1.vitamins A, antixerophthalmic

Important source

Plants form (carotene, C40H56) in green leaves, carrots, etc; is changed in liver to animal form (C₂0H30O), present in fish-liver oil (shark); both forms in egg yolk, butter, milk.

Functions

Maintains integrity of epithelial tissues, especially mucous membrane; needed as part of visual purple in retina of eye.

2. Vitamin D , antirachitic

Important source

Fish-liver oils, especially tuna, less in cod; beef fat; also exposure of skin to ultraviolet radiation.

Functions

Regulates metabolism of calcium and posphorus; promotes absorption of calcium in intestine; needed for normal growth & mineralisation of bones.

3. Vitamin E or tocopherol, antisterility

Important source

Green leaves, wheat germ oil and other vege table fats, meat, milk.

Functions

Antioxidative; maintains integrity of membranes.

* Water soluble vitamin

4. Vitamin (B₁)Thiamine, antineuritic

Important source

Yeast, germ of cereals (especially wheat, peanuts, other legumi nous seed), roots, egg yolk, liver, lean meat.

Functions

Needed for carbohydrate metabolism; thiamine pyrophosphate an essential coenzyme in pyruvate metabolism (stimulates root growth in plants).

5. Vitamin (B₂)Riboflavin

 

Important source

Green leaves, milk, eggs, liver, yeast.

Functions

Essential for growth; forms prosthetic group of FAD enzymes concerned with intermediate metabolism of food and electron-transport system.

6. Vitamin (B3) Nicotinic acid, or niacin, antipellagric

Important source

Green leaves, wheat germ, egg yolk, meat, liver, yeast.

Functions

Forms active group of nicotina mide adenine dinucleotide, which functions in dehydrogenation reactions.

7. Vitamin B Folic acid

Important source

Green leaves, liver, soyabeans, yeast, egg yolk

Functions

Essential for growth and formation of blood cells; coenzyme involved in transfer of single carbon units in metabolism.

8. Vitamin (B₁) Pyridoxine

Important source

Yeast, cereal grains, meat, eggs, milk, liver.

Functions

Present in tissues as pyridoxal phosphate which serve as coenzyme in transamination and decarboxylation of amino acids.

9. Pantothenic acid

Important source

Yeast, cane molasses, peanuts, egg yolks, milk, liver.

Functions

Forms coenzyme A, which cata lyzes transfer of various carbo xylated groups and functions in carbohydrate and lipid metabolism.

10. Biotin (vitamin H)

Important source

Yeast, cereal grains, cane molasses, egg yolk, liver, vegetables, fresh fruits.

Functions

Essential for growth; functions in CO₂ fixation and fatty acid oxidation and synthesis.

11. Vitamin(B12) Cyanocobalamin

Important source

Liver, fish, meat, milk, egg yolk, oysters, bacteria and fermentations of Streptomyces; synthesised only by bacteria.

Functions

Formation of blood cells, growth; coenzyme involved in transfer of methyl groups and in nucleic acid metabolism.

12. Vitamin C , ascorbic acid

Important source

Citrus fruits, tomatoes, vege tables; also produced by animals (except primates and guinea pigs).

Functions

Maintains integrity of capillary walls; involved in formation of intercellular cement.

RESULTS OF DEFICIENCY OR ABSENCE IN HUMANS AND ANIMALS

*Lipid soluble

VITAMIN A

Xerophthalmia (dry cornea, no tear secretion), phrynoderma (toad skin), night blindness, growth retardation.

VITAMIN D

Rickets in young (bones soft, yielding, often deformed); osteomalacia (soft bones), especially in women of Asia.

VITAMIN E

Sterility in male fowls and rats, degeneration of testes with failure of sperma togenesis, embryonic growth disturbances, suckling paralysis and muscular dystrophy in young animals.

VITAMIN K

Blood fails to clot.

* Water soluble vitamin

VITAMIN B1

On diet high in polished rice, beriberi (nerve inflammation); loss of appetite, with loss of tone and reduced motility in digestive tract.

VITAMIN B2

Cheilosis (inflammation and cracking at corners of mouth), digestive disturbances.

VITAMIN B3

Pellagra in humans and monkeys.

VITAMIN B9 (FOLIC ACID)

Anaemia, haemorrhage from kidneys, and sprue (defective intestinal absorption) in humans; nutritional cytopenia (reduction in cellular elements of blood) in monkeys.

VITAMIN B6

Anaemia in dogs and pigs; dermatitis in rats; paralysis (and death) in pig, rats and chicks; growth retardation

VITAMIN B5

Dermatitis in chicks and rats, graying of fur in black rats, "goosestepping" and nerve degeneration in pigs.

VITAMIN H

Dermatitis with thickening of skin in rats and chicks.

VITAMIN B12

Pernicious anaemia, slow growth in young animals; wasting disease in ruminants

VITAMIN C

Scurvy (bleeding in mucous membranes, under skin, and into joints) in humans and guinea pigs

5. MINERALS

Oxygen, carbon, hydrogen and nitrogen are the most common elements that make up 96% of the total weight of a mammal. The next most abundant elements are calcium, phosphorus, potassium, sulphur, sodium, chlorine and magnesium. These make up nearly the remaining 4%.

Fifteen additional elements are required but their total combined amount in mammalian body is less than 0.01% of the body weight.

APPROXIMATE COMPOSITION OF HUMAN TISSUE

Elements per cent body weight

Element

1.Oxygen (65.0%)

2.Carbon (18.0%)

3.Hydrogen (10.0%)

4.Nitrogen (3.0%)

5.Calcium (1.93%)

6.Phosphorus (1.12%)

7.Potassium (0.35%)

8.Sulphur (0.25%)

9.Sodium (0.15%)

10.Chlorine (0.15%)

11.Magnesium (0.05%)

6. WATER

Water is the most important constituent of all living tissue. It forms up to 95% of the fresh weight of some animals. We all know that water is lost through sweat, excretion and evaporation from the respiratory surfaces. It must therefore, be replenished by drinking, through food and in small quantities by metabolic processes of the body like synthesis and oxidation of fats, proteins and carbohydrates.