SS1 Biology Lesson Note on Animal Nutrition and Balanced Diet

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TOPIC: SOME PROPERTIES AND FUNCTIONS OF THE CELL (continued)

CONTENT:

1. Animal nutrition
2. Balanced diet
3. Heterotrophic Nutrition

Sub- Topic 1: Animal Nutrition

All living things feed in order to obtain energy for their daily activities and also to carry out their metabolic processes. Plants can manufacture their own food (i.e. make complex chemical compounds) from simple raw materials (CO₂ and H₂O) through the process of photosynthesis. Plants need minerals to make some of the complex compounds and these are obtained from the soil as mineral ions. Animals however cannot manufacture their own food, they depend directly or indirectly on plants. Nutrients that animals require are present in their diet.

Hamburger and Fries

One of the meals most associated with the United States is a hamburger and french fries. This burger and fries, a daily special, is accompanied by baked beans and coleslaw.

Food Substances

All food taken in by animals can be divided into six groups of food nutrients namely Carbohydrates, Protein, Fats, Vitamins, Minerals, and Water. Fibre/roughage is also an important component of a diet but it is not a nutrient. All these are needed for a balanced diet, for humans.

Carbohydrates, Protein, Fat & oil, and Water are primary food substances and are necessary for the maintenance of life. Minerals salts and Vitamins are welfare food substances and are essential for the well being of an individual.

Types of Food Substances

1. CARBOHYDRATES

These contain the elements carbon (C), hydrogen (H) and Oxygen (O). The ratio of hydrogen to oxygen is 2:1. Carbohydrates are represented by the formula Cx (H₂O)y. The major sources of carbohydrate are Sugar (e.g. glucose, maltose) and starches (e.g. yam, maize, rice).

Types of Carbohydrates

1) Monosaccharides / Simple sugars: These are made up of only one unit of simple sugar e.g.

• Hexose sugars: These consist of six carbon atoms arranged into a ring e.g. glucose, fructose and galactose. They make up the most important energy storage molecules in an organism. Their chemical formula is C₆H₁₂O₆
• Pentose sugars: These consist of five carbon atoms e.g. ribose and de-oxyribose. They are used in the formation of nucleic acids.

2) Disaccharides / Complex sugars: These are formed by the condensation (i.e. chemical bonding of two molecules) of two simple sugar molecules. They are represented by the formula C₁₂H₂₂O₁₁ .

Examples are:

• Maltose (glucose + glucose – H₂O) found in malted cereals and spouting grains.
• Lactose (glucose + galactose – H₂O) found in milk.
• Sucrose (glucose + fructose – H₂O) found in sugar cane stems, ripe sweet fruits, sugar – beet and carrot.

NB         All sugars are sweet and soluble and provide energy in a ready-to-use form.

3) Polysaccharides: These are formed by the condensation of hundreds of simple sugar molecules. They are represented by the general formula

(C₆ H₁₀O₅) _n where n represents a large number. Examples include starch, cellulose, and glycogen (animal starch). Starch and glycogen are insoluble and do not taste sweet.

NB: Condensation is a reaction in which two or more molecules join to form a large molecule with the removal of a molecule of water (H₂O) or some other simple molecule.

Importance of Carbohydrates

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