Download CARBOHYDRATES Carbohydrates are made up of carbon

CARBOHYDRATES
Carbohydrates are made up of carbon, hydrogen and oxygen only. They are
classified according to the number of the simple units they contain as;
a) 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;
i.
Sweet taste
ii.
Dissolve in water
iii.
Can diffuse through a semi permeable membrane
b) Complex sugars
These are sugars composed of two or more monosaccharide molecules.
Complex sugars are of two types;
i)
Disaccharides
General formula C12H22O11
Formed by the process called condensation. i.e. chemical
combination process that results in loss of water molecule.
Example
Glucose
+
maltose
+
C6H12O6
+
condensation
water
+
C12H22O11
Glucose
C6H12O6
condensation
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.
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Disaccharides have the following properties
a) Sweet taste
b) Colourless crystalline substance
c) Soluble in water
d) Less diffusion across a semi permeable membrane compared
to monosaccharides
ii)
Polysaccharides:
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;
a) Starch, stored in plant parts such as cassava, potato, and root
tubers.
b) Glycogen: stored form of carbohydrate in animals mainly in
muscle and liver
c) Cellulose, found in plant cell walls. It consists of a long chain
of glucose.
They have the following general characteristics;
a) Insoluble in water
b) Cannot diffuse across a semi permeable membrane
c) They are not sweet
Functions of carbohydrates
1. Energy production during respiration
2. Formation of structures such as cell walls of plants made of cellulose
3. Cellulose is used in the manufacture of papers, synthetic fibers, films
and explosives.
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PROTEINS
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
H
R
C
COOH
NH2 _ amino group
NH2
There are about 20 amino acids that make up proteins in living organisms.
TYPES OF AMINO ACIDS
There are two types of amino acids;
1. 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.
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2. 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,
1. First class proteins. These are the proteins that contains all the essential
amino acids e.g. soya beans, and most animal proteins.
2. 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
1. Dissolve with difficulty in water to form colloidal solution (sticky like glue)
2. They have large molecules and so cannot pass through cell membranes.
3. Proteins coagulate when boiled. This is what happens when the egg
albumen is boiled.
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FUNCTIONS OF PROTEINS
1. Vital for the formation of new cells and replacement of old ones hence
growth.
2. They help in maintaining the composition of protoplasm.
3. They are used in the formation of various structures in the body eg
keratin in the hair, nails, hooves, horns, feathers etc.
4. They are important in the formation of enzymes, which speed up
chemical reactions in organisms..
5. They form antibodies which defend the body against diseases.
6. Coordination of activities in the body as a hormone constituent.
7. 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
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.
A
Animal fat and
Normal growth.
 Poor night vision
RETINAL
oils, milk, liver,
Keeps skin and
[xeropthalamia] or
green vegetables,
eyes healthy.
night blindness.
carrots, green
Increases
 Poor growth.
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paper.
resistance to
 Reduced
disease.
resistance to
diseases.
B1
Yeast, egg, liver,
As a coenzyme in  Disease of the
THIAMINE
pulses,
cell respiration for
muscles, nerves
Tomatoes,
the normal
and heart.
unpolished
functioning of the
 Loss of appetite.
cereals.
heart and
 Circulatory failure.
nerveous system
 Paralysis.
 Digestive trouble.
 Wasting away of
the muscles.
 Poor assimilation
loss of weight.
B2
Meat, milk, other
RIBOFLAVIN as for B1
For cell
 Slow growth
respiration
 Skin diseases
For skin health
 Sore mouth.
PELLAGRA
PP
Meat, fish, wheat,
For cell
NIACINICOT
eggs, liver, green,
respiration
INIC ACID
vegetatables.
-
A skin disease
-
Mental disorder
-
Abdominal
pains
-
Diarrhea
-
Pigmentation in
exposed areas
of the chest
C
Fresh citrus fruits,
-
Ascorbic acid green vegetables,
Increased
SCURVY
resistance
Irish potatoes
-
-
Pains and
to disease
swelling of the
Formation
joints and
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of collagen
-
gums,
Healing of
-
wounds
Loosening of
teeth, bleeding
of the gums,
skin and
mucous
membranes
-
Poor wound
healing
-
General
weakness
D
Milk, eggs, fish,
Hardening of
RICKETS
Calciferol
liver, oil and
bones and teeth
(faulty bone formation
E
butter.
in children)
Skin of man in
Teeth diseases
sunlight
(dental caries)
Vegetable oil,
(Tocopherol) eggs, liver
Promotes fertility
Sterility in animals
(in rats)
e.g. rats
K
Green vegetables, Clotting of blood
Delayed clotting of
Phyloquinon
tomatoes and liver
blood
e
Mineral elements
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
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-
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
FOOD
ELEMENT
SOURCES
IRON
CALCIUM
IMPORTANCE
DEFFICIENCY
Beef, liver,
Constituent of
Reduced red
kidney, green
haemoglobin
blood cell count
vegetables, G
and oxygen
nuts, cocoa,
transport resulting
beans, eggs.
in ANAEMIA
Vegetables, fish,
Constituent of
milk, bread,
bones and teeth
eggs.
which it is
responsible for
hardening
For muscle
contraction.
For clotting of
blood.
Activator of
enzymes.
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RICKETS
DELAYED
MUSCLE
CONTRACTION
PHOSPHOROUS
Most foods
Formation of
Not likely to be
(dairy products,
ATP.
deficient since it is
meat, fish,
poultry, nuts.)
FORMATION OF
BONES AND
TEETHS
present in most
foods especially
protein
Constituent of cell
membranes
IODINE
SODIUM
Sea fish, iodized
Constituent of the
GOITRE (swelling
salts.
hormone
of the thyroid
thyroxine.
glands)
Transmission of
MUSCLE CRUMP
nerve impulses
(i.e. sharp pains in
Common salt.
Muscle
muscles)
contraction
FLUORINE
Added to
Constituent of
Weak teeth (in
drinking water.
bones and teeth.
children).
Prevents dental
carries
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