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Significance of Carbohydrates

y As an energy Source

The main source to obtain energy for the activities of organisms is the

 carbohydrate. The Monosaccharides (Glucose) produced due to hydrolysis

 of those compounds release energy.

y As a storage compound

y As a structural component in plant cell wall

y As a constituent of Nucleic acid

Tests to identify Carbohydrates

The below mentioned tests can be conducted to test Starch, Monosaccharides

and Disaccharides which are some of the identified Carbohydrates in foods.

Starch test

y Small amount of food is obtained and grind well with water.

y A drop of Iodine solution is added to the above solution.

 Purplish blue color appears

Test for Glucose

y A solution of Glucose is obtained into a test tube.

y Few drops of Benedict solution to the above solution is added.

y The above solution is immersed in a water bath and heated.

y Can observe color changes as below.

Blue Green Green yellow Orange Brick red precipitate

Test for (Sucrose)

y A sucrose solution is obtained into a test tube.

y Few drops of Benedict solution is added to it.

y The test tube is immersed in a water bath and heated.

No color change.

y Few drops of diluted Sulphur acid (H2

SO4

) is added to a freshly

prepared sugar solution and heated.

y Next few drops of Benedict solution is added to it.

y Can observe color changes as below.

Blue Green Green yellow Orange Brick red precipitate

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1.2 Proteins

Protein is an essential constituent in all living cells. Carbon(C) Hydrogen (H),

Oxygen (O) and Nitrogen (N) are always present in proteins. Sometimes Sulphur

can also be present.

17% of the mature human body is composed of proteins. Protein is a complex

molecule made up of polymerized amino acid molecules. Meat, fish, egg white

cereals are some of the foods rich with proteins.

For extra knowledge

y Amino acids

Below is the structure of a typical amino acid molecule.

whisked ld. av C ldfndlais,a lava

R

H

NH2 COOH Carboxyl

group

Amino

group

R-represents a group containing both Carbon (C) and Hydrogen (H). Due to the

change in R group, 20 different amino acids are present. All proteins present in

organisms from bacteria to human are made up of these 20 different amino acids

combined in different sequences.

The simplest Amino acid is Glycine. Here Hydrogen (H) is present as the

R group.

C NH2

COOH

H

H

Some amino acids cannot be synthesized within the body. So they have to be

taken from outside with food. Therefore, they are known as essential amino

acids.

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For extra knowledge

• Significance of Proteins

y As an energy source

When energy supply from Lipids and Carbohydrates is not sufficient

protein is used in energy generation.

y To make structural components

Proteins are important components in making cell membrane. Hairs and

feathers also contain keratin protein.

y As enzymes

All the bio-chemical reactions take place in organisms are catalyzed by

enzymes. The enzymes are proteins.

y As hormones

Some hormones are proteins which involve in homeostasis and coordination

of organisms.

y As antibodies

The antibodies that are produced in the body to protect the body against

microorganisms that enter into the body are proteins.

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Test to identify proteins

 Burette test

ΠA solution made by grinding dhal or an egg yolk is obtained into a test tube.

ΠAn extra amount of Sodium hydroxide (Nao) and then few

drops of Copper Soleplate is added in to it.(CuSO4

)

Solution turn to purple color

■ Enzymes

The special proteins (organic catalysts) that are produced within the organism to

increase the rate of bio-chemical reactions are known as enzymes.

For example to convert Sucrose into Glucose, Sucrose has to be heated with a dilute

acid. But the enzymes present in the digestive system do the same reaction at a low

temperature.

Therefore the activity of enzyme is to catalyze the bio-chemical reactions.

Activity of Amylase on Starch

Materials required

y Flour, Amylase, Test tube, white porcelain tile, Iodine solution

Method

y Put 2ml of Starch solution into a test tube.

y Add 2ml of Amylase (Filter a solution of ground germinating green gram

(Mung) seedlings) into it and mix well.

y Get a drop from the solution after 2 minutes and place it on a white

porcelain tile and add a drop of Iodine onto the drop of mixture.

y Continue same procedure for about 20 minutes in 2 minute intervals.

Activity - 01

The blue color of the drop obtained from the mixture gradually reduces with

time and finally obtains the color of Iodine (yellow /brown color)

Starch gives black blue color with Iodine but it does not give color change

with Iodine after 20 minutes as there is no Starch there. That is because Starch is

converted to Maltose by Amylase enzyme.

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1'3 Lipids

Fats and oils belong to this group. Lipids which are solid at room temperature are

called fats and liquids are called oils.

Similar to carbohydrates, fats also contain Carbon, Hydrogen and Oxygen as

constituent elements. But the ratio of Hydrogen to Oxygen in fats are very much

higher than carbohydrates. Lipids are insoluble in polar solvents including water.

They are soluble in organic solvents.

Ground nut, coconut, gingelly, butter and margarine are examples for foods which

contain lipids.

Fatty acids and glycerol react to form Lipids.

Fatty acids ¬ Glycerol Lipids ¬ Water

• Significance of Lipids

y As an energy source

Lipids act as an energy source as carbohydrates and proteins. More energy

is produced during burning of lipids.

y To form different structural components

Lipid is one of the most important compounds in cell membrane.

(Specially phosphor lipids and cholesterol)

y For conservation of water

The wax known as cutting present on the surface of the plant body conserve

water. Most animals' body covering also contains wax which helps to avoid

desiccation as it is impermeable to water.

y To maintain the body temperature

Warm blooded animals such as birds and mammals possess a hypodermal

fat layer which acts as a thermal insulator. It helps to maintain their body

temperature.

y To protect internal body organs

The fat layer surrounds the organs and structures in the body and absorbs

external shocks. Thereby provides protection.

y To synthesize some hormones

Some Hormones of vertebrates (Estrogen, Testosterone, Cortisone) are

lipid compounds.

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Test to identify lipids

Sudan III test

• Some amount of gingelly oil or coconut oil is added into a test tube.

y Sudan III reagent is added into it.

Appearance of red fat globules

For extra knowledge

Fatty acids can be divided into two groups as follows.

 fatty acids

saturated fatty acids unsaturated fatty acids

Saturated fatty acids

Fatty acids which contain only single bonds within Carbon atoms are

called saturated fatty acids. Saturated fatty acids exist in room temperature

as solids or semi-solids.

Unsaturated fatty acids

Fatty acids which contain one or several double bonds within Carbon

atoms are called unsaturated fatty acids.

Unsaturated fatty acids exist in room temperature as liquids.

1'4 Nucleic Acids

Nucleic acid is the most important molecule out of the main bio molecules in

living matter in genetical aspect. It is a linear polymer made up of large number of

nucleotides. It contains Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)

and Phosphorous (P).

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For knowledge

Each nucleotide is made up of 3 components. They are ;

1. Nitrogenous base

2. Pentose sugar group

3. Phosphate group

Figure 1.3 - A nucleotide

Phosphate

Pentose Sugar group

Nitrogenous

base

• DNA

The structural unit of DNA is Deoxy rib Nucleotide. DNA transfers genetic

characteristics from generation to generation

• RNA

Except DNA, the other nucleic acid present

Figure 1.4- The structure of

a DNA molecule

in organisms is RNA.

The structural unit of RNA is

Ribonucleotide.

Protein synthesis is the function of RNA.

• Significance of Nucleic acidic

y Important in storage of genetic information of organisms.

y Important in transferring genetic information from generation to generation.

y Important in protein synthesis process.

y Important in controlling all cellular activities in a cell. The information to

control cellular activities is present in DNA.

y RNA is important in storing genetic information of some viruses.

y The variations occur in DNA due to mutations are important in evolution.

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The above bio molecules contain mainly Carbon (C), Hydrogen (H),Oxygen (O)

and Nitrogen (N). We will conduct below mentioned activities to confirm the

presence of those elements.

Activity - 02

Identification of water as a constituent in food

Materials required

Meat, Egg shell, Plant leaves, Crucible

Method

y Grind /crush meat, egg shell, and leaves separately.

y Put them separately into the crucible and heat them.

y During heating, hold a glass sheet above the crucible.

y Use Anhydrous Cobalt Chloride / Copper Soleplate to identify

whether the liquid drops on the glass is water.

Blue colored Anhydrous Cobalt Chloride turn to pink and white colored

Anhydrous Copper Soleplate turn to blue. Then it is confirmed that water is formed

on the glass sheet. Therefore the food that is used for the experiment contains water

as a constituent.

Activity - 03

Identification of presence of Carbon(C) in bio-molecules

Materials required

y Several crucibles, Spinach Stems, Piece of fish, Chick pea

Method

y Make pulps by crushing all above materials separately.

y Put them separately into crucibles and heat well.

y The final residue obtained should be rubbed against a white paper.

Lines drawn due to coal is observed.

Can confirm the food that is used for the experiment contains Carbon (C).

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Activity - 1'4

Identification of presence of Nitrogen(N) in bio-molecules

Materials Required

Two test tubes, solution of Sodium Hydroxide, solution of Copper

Soleplate, egg white, piece of fish.

Method

y Crush fish thoroughly, add water and mix well. Filter the solution.

y Put 2ml of the fish extraction and egg white into separate test tubes.

y Add equal volume of sodium hydroxide.

y Add few drops of copper caliphate to it.

Purple color appears in the solution and this confirms the presence of Protein in

food. As Nitrogen is a constituent of Proteins, it is confirmed that the above tissues

contain Nitrogen.

1'5 Water

The highest proportion of the body mass of living organisms is composed of water

which is an inorganic compound. Two third (2/3 rd) of the body weight of most of

organisms is by water. Water is an essential medium for the maintenance of living

matter. The table below, shows the specific properties of water and contribution of

them to the maintenance of life.

Assignment - 1.1

As a group, collect information about specific features of water and functions

to maintain life. Use internet, newspapers and other journals. Present those

information in a creative way to the class.