BIOLOGY NOTES|FORM TWO|NUTRITION

NUTRITION

Taking food to maintain life- feeding

Importance

• Growth
• Body building and repair
• Energy
• Maintain health (body protection)

Types

-Parasitic.

Organisms depend on other organisms e.g. Lice, mosquito feed on humans.

-Saprophytic.

Feed on dead organisms.

-Holozoic

Animal nutrition

Involves taking in food through mouth.  Extra material is removed through egestion.

– Ingestion

– Digestion

– Absorption

– Egestion (Defecation)

1. Autotrophic Nutrition (Autotrophs)

Type of nutrition where by organisms makes their own food.

1. Photosynthesis- process of converting solar energy to chemical energy.
2. Chemosynthesis- building complex materials using energy from chemicals.

DIET

Diet is the collective amount of food that you eat.  Is the sum total of the food materials taken in by an organism in a given meal.

Balanced diet.

Is the right amount of food (nutrients) taken in their correct proportions and right amount.

Food substances are chemicals found in food used by the body to maintain life

Types of food substances:

1. Carbohydrates
2. Proteins
3. Lipids (oils & fats)
4. Mineral salts
5. Water
6. Vitamins
7. Roughage

MALNUTRITION

Is a wrong nutrition by eating too much, too little or just a few food substances.

Diseases caused by malnutrition

Kwashiorkor– it is a Ghanaian word which simply means disease of the first child when second one is born.

Food substances

Carbohydrates – are substances which contain carbon, hydrogen and oxygen. Hydrogen and oxygen are in the ration of 2:1.

Composition of carbohydrate

• Carbon, oxygen and hydrogen
• Simplest sugar or saccharide

Classification of carbohydrates

There are 3 types of carbohydrates.

1. Monosaccharide- it is made up of one saccharide e.g. Glucose, fructose and galactose.
2. Disaccharide- made up of two saccharides chemically combined together e.g. Sucrose, glucose and fructose

(Milk, sugar) lactose → Glucose + galactose

Maltose →Glucose + glucose

3. Polysaccharide – made up of more than 2 saccharides chemically combined. E.g. Starch, cellulose, glycogen.

Condensation- is a process of bringing two molecules together chemically with release of water.

Glucose + glucose → Maltose + water

Disaccharide and polysaccharides are chemically combined.  The chemical combination is called condensation.

Hydrolysis- is a process of breaking down complex carbohydrates chemically by addition of water.

Reducing sugars and non –reducing sugars

A reducing sugar is any carbohydrate that can convert copper II sulphate into copper I oxide.

The reducing sugar has free functional groups which reduce the copper II sulphate to copper I oxide.   The functional groups are either KETONES or ALDEHYDES.  All monosaccharides and disaccharides except sucrose are reducing sugars.
LIPIDS

A non reducing sugar is a carbohydrate that can’t convert copper II sulphate into copper I oxide.  The non reducing sugar doesn’t have free functional groups which reduce the copper II sulphate to copper I oxide.  Sucrose is the only non reducing disaccharide known so far the polysaccharides do not react with the copper sulphate.

Properties of carbohydrates:

1. Monosaccharides
   1. Colourless
   2. Soluble in water
   3. Tastes sweet
   4. Diffuses through semi permeable membrane
   5. Converts copper sulphate to copper I oxide – basis for test of reducing sugars

1. Disaccharides
2. Colourless
3. Very soluble in water
4. Tastes very sweet
5. Diffuses slowly through semi permeable membrane
6. Except for sucrose they can convert copper II sulphate to copper I oxide

1. Polysaccharide
2. Starch
3. Insoluble in water
4. Forms a gel when boiled with water and cooled
5. Tasteless
6. It gives you a blue –black colour with iodine solution
7. Cellulose
8. Insoluble in water
9. Completely hydrolysed or broken down to sulphur acid to simple sugar
10. Reacts with iodine solution and changes from white to light blue.

3. Glycogen
4. Soluble in water
5. Gives a reddish brown colour with iodine solution

Natural sources of carbohydrates.

1. Root crops – yams, cassava, potatoes, beet, carrots.
2. Fruits- oranges, mangoes, apples, bananas, pineapple.
3. Cereals- maize, wheat, rice, millet, sorghum
4. Pulses- beans, peas
5. Stem- sugarcane
6. Leaves- onions, spinach

Importance of carbohydrates:

1. Provides energy
2. Structural substances
3. Storage substances

PROTEINS

These are organic compounds made up of carbon, hydrogen, oxygen, nitrogen and some proteins. Contain sulphur and phosphorus. Simplest unit is amino acid.

Properties of protein:

1. Insoluble in water
2. Coagulates on heating
3. Reacts with millon reagent to form a red colour. This is the basis for the millons reagent test for proteins.
4. Reacts with sodium hydroxide and copper II sulphate to produce a purple colour which intensifies on heating. This is the basis for BIURET TEST for proteins.
5. Very large molecules which diffuse very slowly across membranes.

Natural sources of proteins:

1. Milk and milk products
2. Fish
3. Eggs
4. Beef
5. Pork
6. Chicken
7. Beans
8. Peas

Examples of proteins:

1. Myosin and Myoglobin in muscles
2. Albumin in eggs
3. Keratin in hair and nails
4. Haemoglobin in blood (RBC)

Importance of proteins:

1. Materials for body building
2. Used as strengthening and structural material
3. Used as storage materials
4. Provides energy during starvation
5. Used for protection

LIPIDS

Organic compounds containing elements of carbon, hydrogen and oxygen with hydrogen being far too many compared to oxygen.

Example:

¢57H 104 06 (OLIVE OIL)

¢57 H 110 06 (BEEF FAT)

Composition

They are 2 types of lipids: a) Fats b) oils

Fats:  are solid at room temperature, while oilsare liquids. Fats are mainly of animal origin while oils are of plant origin. The smallest unit of both oils and fats is fatty acids and glycerol.

Properties of Lipids:

1. Insoluble in water
2. Dissolves in organic solvents e.g. Chloroform, ethanol.
3. When oil is shaken in water the oils breaks down into droplets which disperse in water.
4. When rubbed against paper, the paper becomes translucent.
5. In a mixture of oils and water, oil takes up SUDAN II and becomes red leaving the clear confirmatory test for lipids.
6. Reacts with osmic acid to form a black colour.

Examples of lipids:

1. Animal fats from meat
2. Olive oils from olives
3. Ground nut oil from ground nuts
4. Coconut oil from coconuts
5. Cashew nut oil from cashew nuts
6. Palm oil from palm fruits
7. Corn oil from corn/maize
8. Sunflower oil from sunflower seeds