Carbohydrates are made up of carbon, hydrogen and oxygen only. They are classified according to the number of the simple units they contain as;
- Monosaccharides: (simple sugars)
They have the general formula C6H12O6. Examples are glucose, fructose (found in juicy fruits) and galactose (milk sugar).
They have the following general physical properties;
- Sweet taste
- Dissolve in water
- Can diffuse through a semi permeable membrane
- Complex sugars
These are sugars composed of two or more monosaccharide molecules. Complex sugars are of two types;
General formula C12H22O11
Formed by the process called condensation. i.e. chemical combination process that results in loss of water molecule.
Glucose + Glucose condensation maltose + water
C6H12O6 + C6H12O6 condensation C12H22O11 + H2O
The disaccharides may be reconverted back to monosaccharides by a process called hydrolysis. Hydrolysis involves the addition of water in a chemical breakdown of larger molecules into smaller forms.
Disaccharides have the following properties
- Sweet taste
- Colourless crystalline substance
- Soluble in water
- Less diffusion across a semi permeable membrane compared to monosaccharides
These are formed by further condensation of more than two molecules of monosaccharides. They have the general formula (C6H10O5)n where n represents several sugars. Polysaccharides include the following;
- Starch, stored in plant parts such as cassava, potato, and root tubers.
- Glycogen: stored form of carbohydrate in animals mainly in muscle and liver
- Cellulose, found in plant cell walls. It consists of a long chain of glucose.
They have the following general characteristics;
- Insoluble in water
- Cannot diffuse across a semi permeable membrane
- They are not sweet
Functions of carbohydrates
- Energy production during respiration
- Formation of structures such as cell walls of plants made of cellulose
- Cellulose is used in the manufacture of papers, synthetic fibers, films and explosives.
Proteins are body building foods. They are made up of carbon, hydrogen, nitrogen, oxygen and sometimes sulphur and phosphorus. Compared with most other organic molecules, protein molecules are huge and therefore cannot pass through semi-permeable membrane.
Proteins are made up of small unit molecules called amino acids.
The nature of protein is determined by the types of amino acids it is made of.
Amino acids have the general formula
R C COOH NH2 _ amino group
There are about 20 amino acids that make up proteins in living organisms.
TYPES OF AMINO ACIDS
There are two types of amino acids;
- Essential amino acids.
These are amino acids that can not be synthesized by the body and have to be supplied in the diet. Examples are valin, arginine, leusin, lysine, phenydalanine etc. there are 10 essential amino acids.
- Non essential amino acids.
These are the amino acids which can be synthesized by the body and therefore need not to be available in the died.exaples include glycine, alanine, asparticacid, serine, praline etc.
There are also 10 non essential amino acids.
CLASSIFICATION OF PROTEINS
Proteins can be classified into two,
- First class proteins. These are the proteins that contains all the essential amino acids e.g. soya beans, and most animal proteins.
- Second class proteins. These are proteins that lack one or more of the essential amino acids. They include mostly plant proteins and a few animal proteins
FORMATION OF PROTEINS
Proteins are made up of many amino acid units joined together through peptide bonds. When two amino acids are joined together a dipeptide is formed. The chemical process involved is called condensation in which water is formed or lost.
When many amino acids are joined together a polypeptide chain is formed. The nature of a particular protein depends on the types and sequence of amino acids from which it is made.
PROPERTIES OF PROTEINS
- Dissolve with difficulty in water to form colloidal solution (sticky like glue)
- They have large molecules and so cannot pass through cell membranes.
- Proteins coagulate when boiled. This is what happens when the egg albumen is boiled.
FUNCTIONS OF PROTEINS
- Vital for the formation of new cells and replacement of old ones hence growth.
- They help in maintaining the composition of protoplasm.
- They are used in the formation of various structures in the body eg keratin in the hair, nails, hooves, horns, feathers etc.
- They are important in the formation of enzymes, which speed up chemical reactions in organisms..
- They form antibodies which defend the body against diseases.
- Coordination of activities in the body as a hormone constituent.
- Proteins may be used for respiration in circumstances where carbohydrates and lipids are not present.
Deficiency of proteins causes a disease called kwashiorkor. Occurs normally in children between ages of 6 months and 4 years because of the high energy requirement and growth after weaning.
Vitamins are organic constituents of food that are required in small amounts for a variety of metabolic processes. They often form part of enzymes.
Vitamins are of two groups, i.e. water soluble and fat soluble vitamins. Fat soluble vitamins include A, D, E, and K. water soluble vitamins include B and C
|VITAMIN||FOOD SOURCES||FUNCTIONS||DEFICIENCY AND SYMPTOMS.|
|Animal fat and oils, milk, liver, green vegetables, carrots, green paper.||Normal growth.
Keeps skin and eyes healthy.
Increases resistance to disease.
|v Poor night vision [xeropthalamia] or night blindness.
v Poor growth.
v Reduced resistance to diseases.
|Yeast, egg, liver, pulses,
Tomatoes, unpolished cereals.
|As a coenzyme in cell respiration for the normal functioning of the heart and nerveous system||v Disease of the muscles, nerves and heart.
v Loss of appetite.
v Circulatory failure.
v Digestive trouble.
v Wasting away of the muscles.
v Poor assimilation loss of weight.
|Meat, milk, other as for B1||For cell respiration
For skin health
|v Slow growth
v Skin diseases
v Sore mouth.
|PP NIACINICOTINIC ACID||Meat, fish, wheat, eggs, liver, green, vegetatables.||For cell respiration||PELLAGRA
– A skin disease
– Mental disorder
– Abdominal pains
– Pigmentation in exposed areas of the chest
|Fresh citrus fruits, green vegetables, Irish potatoes||– Increased resistance to disease
– Formation of collagen
– Healing of wounds
– Pains and swelling of the joints and gums,
– Loosening of teeth, bleeding of the gums, skin and mucous membranes
– Poor wound healing
– General weakness
|Milk, eggs, fish, liver, oil and butter.
Skin of man in sunlight
|Hardening of bones and teeth||RICKETS
(faulty bone formation in children)
Teeth diseases (dental caries)
|Vegetable oil, eggs, liver||Promotes fertility
|Sterility in animals e.g. rats|
|Green vegetables, tomatoes and liver||Clotting of blood||Delayed clotting of blood|
These are in organic food constituents required by the body in small amounts but their deficiency affects the functioning of the body leading to a deficiency disease or symptom
Mineral elements can be grouped into
- Essential mineral elements; i.e. those required in large amounts and include; Na, P, K, Ca and Fe
- Non essential mineral elements; these are required in small amounts and include; Zn, Mo, Co, B and Mn. They are also called trace elements.
Table 3.4 Giving facts about some of the mineral elements required by man
|MINERAL ELEMENT||FOOD SOURCES||IMPORTANCE||DEFFICIENCY|
|IRON||Beef, liver, kidney, green vegetables, G nuts, cocoa, beans, eggs.||Constituent of haemoglobin||Reduced red blood cell count and oxygen transport resulting in ANAEMIA|
|CALCIUM||Vegetables, fish, milk, bread, eggs.||Constituent of bones and teeth which it is responsible for hardening
For muscle contraction.
For clotting of blood.
Activator of enzymes.
DELAYED MUSCLE CONTRACTION
|PHOSPHOROUS||Most foods (dairy products, meat, fish, poultry, nuts.)||Formation of ATP.
FORMATION OF BONES AND TEETHS
Constituent of cell membranes
|Not likely to be deficient since it is present in most foods especially protein|
|IODINE||Sea fish, iodized salts.||Constituent of the hormone thyroxine.||GOITRE (swelling of the thyroid glands)|
|SODIUM||Common salt.||Transmission of nerve impulses
|MUSCLE CRUMP (i.e. sharp pains in muscles)|
|FLUORINE||Added to drinking water.||Constituent of bones and teeth.
Prevents dental carries
|Weak teeth (in children).|