Sri Lanka Job Vacancies - National Aquatic Research Research Agency

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The bodies of all organisms are composed of variety of chemical compounds. These

chemical compounds are formed by the bonding of naturally existing elements in

different ways.

There are only about 25 elements in the living body out of the 92 elements present

in nature. They are present at different locations in the body in different forms.

The most common 4 elements in the living body are Carbon, Hydrogen, Oxygen and

Nitrogen. Other than above Sulphur, Phosphorous, Sodium, Potassium, Calcium,

Magnesium, Iron and Chlorine are essential for the survival of organisms.

The below figure 1.1 shows the percentages of main elements in the human body.

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Oxygen

Carbon

Hydrogen

Nitrogen

Others

Figure 1.1- Percentages of 4 common elements in the

human body (mass basis)

Chemical compounds that build up living matter can be divided into two categories

as orgonic compounds and inorganic compounds. Compounds which contain Carbon

are known as organic compounds and compounds which do not contain Carbon are

known as inorganic compounds. (Carbon dioxide, Carbon monoxide,Carbonates

and Bicarbonates are some of the inorganic compounds which contain Carbon)

Those organic compounds that build up the living body or living matter are known

as bio molecules. They are:

² Carbohydrates

² Proteins

² Lipids

² Nucleic acids

These are considered as the main types of bio molecules. Instead of these four

types, Vitamins are also one of the organic compounds found in living matter.

2 For free distribution 3 For free distribution

Water, minerals and gases are some of the inorganic molecules that are essential

for the maintenance of life.

Element Percentage

based on

mass%

Locations present in human body

O 65 All fluids, tissues, bones, proteins

C 18 everywhere in the body

H 10 All fluids, tissues, bones, proteins

N 3 All fluids, tissues, proteins

Ca 1.5 Brain, lungs, kidneys, liver, heart,

thyroid gland, muscles, bones

P 1.0 Urine, bones

K 0.35 Enzymes

S 0.25 Proteins

Na 0.15 All fluids, tissues

Mg 0.05 Brain, lungs, kidneys, liver, heart,

thyroid gland, muscles

Cl 0.2 Skin cells

Fe 0.007 Haemoglobin in blood

I 0.0002 Hormones in thyroid gland

For extra knowledge

1'1 Carbohydrates

This is the most abundant organic compound on earth. They are produced during

the photosynthesis of green plants. Potato, sweet potato, grains, sugar, flour are

examples for foods which contain carbohydrates.

The main elemental composition of carbohydrates is Carbon (C), Hydrogen

(H) and Oxygen (O).

Hydrogen and oxygen combine in 2:1 ratio in carbohydrates.

Common molecular formula

Cx

 (H2

O) y

2 For free distribution 3 For free distribution

² Monosaccharides

Type of

monosaccharide

Location it's

present Other facts

4 For free distribution 5 For free distribution

² Disaccharides

Two Monosaccharides join to form a Disaccharide. During this process a water

molecule is released. In the same way relevant Monosaccharides can be obtained

by hydrolyzing Disaccharides. Disaccharides are sweet, water soluble crystals.

Monosaccharide + Monosaccharide Disaccharide + Water molecule

2 C6

H12O6 C12H22O11 + H2

O

Maltose, Sucrose and Lactose are examples for disaccharides.

The characters of disaccharides are discussed in the table below.

Table 1.2 - Characters of different types of disaccharides

Type of

disaccharide

Location it's

Present

Other Facts

Maltose Germinating

seeds

• Union of two glucose molecules

forms a Maltose molecule .

Glucose ¬ Glucose Maltose ¬Water

• An intermediate product of starch hydrolysis

Sucrose White and

brown Sugar

Sugar cane and

Beet

Some fruits

Phloem sap in

trees

• Union of a Glucose molecule with a Fructose

molecule forms a Sucrose molecule

 Glucose ¬ Fructose Sucrose¬Water

Lactose In dairy products • Union of a Glucose molecule with a

Galactose molecule forms a Lactose

molecule

Galactose ¬ Glucose Lactose¬Water

• The only sugar that is absent in plants

• Not sweet as Sucrose

• The percentage of Lactose in cows milk

according to the composition is 4% - 6%

• The percentage of Lactose in human milk

according to the composition is 6% - 7%

4 For free distribution 5 For free distribution

² Polysaccharides

Polymerisation of a large number of monosaccharides form a polysaccharide

molecule. Hydrolysis of Polysaccharide results relevant monosaccharides.

Insoluble in normal water. They are not crystals. Cellulose, Starch and Glycogen

are examples for polysaccharides. The structural unit of Cellulose, Starch and

Glycogen is Glucose , but their properties are different according to the number of

Glucose molecules and how they are bound with each other.

The characters of polysaccharides are discussed in the table below.

Table 1.3 - Characters of different types of polysaccharides

Type of

polysaccharide

Location it's

Present

Other Facts

Cellulose Cell wall of

plant cells

In fibres

• It is not digested in the human digestive

system, but it helps to avoid constipation.

Starch Grains, Yams,

Jak, Bread

Fruit

• The type of carbohydrate that stores in

plants is starch.

Glycogen Animal liver

and muscles

y The type of carbohydrate that stores in

animal body is Glycogen

For extra knowledge

Figure 1.2 - Structure of a

glucose molecule