EXERCISES

Q1. What are macromolecules? Give examples.
Answer: Macromolecules are large chemical compounds found in living organisms that have very high molecular weights, usually above ten thousand daltons. They are also called biomacromolecules. The main macromolecules present in living tissues are proteins, polysaccharides, and nucleic acids, which are polymeric substances made up of repeating smaller units. For example, proteins are made of amino acids, polysaccharides of sugars, and nucleic acids of nucleotides. Although lipids are found along with these molecules, they are not true macromolecules because their molecular weight is much smaller, generally less than 800 daltons.

Q2. What is meant by tertiary structure of proteins?
Answer: The tertiary structure of a protein refers to the complex three-dimensional folding of its long polypeptide chain, which gives it a compact and globular shape. This folding is stabilized by different types of bonds such as hydrogen bonds, disulphide bonds, ionic interactions, and hydrophobic forces. The specific 3D conformation determines the biological activity of the protein and enables it to perform precise functional roles in the body.

Q3. Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers.
Answer:
Small molecular weight biomolecules are simple compounds such as sugars, amino acids, and fatty acids that play crucial roles in biological systems and industrial applications. These compounds are often manufactured by chemical synthesis, fermentation, or extraction from natural sources.

These biomolecules form the foundation of various industrial processes and are widely utilized in food, healthcare, pharmaceutical, and cosmetic sectors.

Q4. Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins.
Answer: Several proteins are used as medicines and in other fields.
Therapeutic proteins include:

1. Insulin, used to treat diabetes.
2. Antibodies, used to fight infections and in cancer therapy.
3. Trypsin, used in wound healing.
4. Growth hormone, used for growth disorders.
5. Clotting factors (VIII and IX), used to treat hemophilia.

Other uses of proteins:

1. Cosmetics: Collagen in skin care, keratin in hair products.
2. Food industry: Casein in cheese and gelatin in desserts.
3. Research: Enzymes and receptors used in labs and diagnostics.

Q5. Explain the composition of triglyceride.
Answer: A triglyceride is made of two components, one molecule of glycerol and three molecules of fatty acids.
Each fatty acid is attached to glycerol by an ester bond, forming a tri-ester structure.
Triglycerides are also known as fats or oils depending on whether they are solid or liquid at room temperature.

Q6. Can you attempt building models of biomolecules using commercially available atomic models (Ball and Stick models)?
Answer: Yes, we can build models of biomolecules using ball-and-stick kits available in the market.
This helps to visualize their three-dimensional shapes, which is very useful in understanding molecules like amino acids and lipids.
By studying these models, we can easily see how structure affects the molecule’s function, such as the folding of proteins.

Q7. Draw the structure of the amino acid, alanine.
Answer: Amino acids have both an amino group (−NH₂) and a carboxyl group (−COOH) attached to the same carbon atom, called the α-carbon.
The structure also includes a hydrogen atom and a variable side chain (R group).
In alanine, the R group is a methyl group (−CH₃).
So, the structure of alanine can be represented as:

   COOH
    |
H – C – NH2
    |
   CH3

Q8. What are gums made of? Is Fevicol different?
Answer: Gums are natural substances made mainly of polysaccharides secreted by plants to protect wounds or injuries. They are complex carbohydrates.
Fevicol, however, is not a natural gum. It is made of polyvinyl acetate (PVA), which is a synthetic polymer used as an adhesive.
So, yes, Fevicol is chemically different from natural gums.

Q9. Find out a qualitative test for proteins, fats and oils, amino acids and test any fruit juice, saliva, sweat and urine for them.
Answer: Different biomolecules can be identified using specific chemical tests.
Here are some common ones:

When tested in samples:

• Fruit juice: Trace amino acids, no fats or proteins.
• Saliva: Proteins present (enzymes like amylase).
• Sweat: Trace amino acids only.
• Urine: No proteins or fats; trace amino acids may be present.

Q10. Find out how much cellulose is made by all the plants in the biosphere and compare it with paper manufactured by man.
Answer: Plants produce enormous amounts of cellulose every year — roughly around 10¹¹ tons globally. It forms the main structure of plant cell walls.
Humans, on the other hand, produce about 400–500 million tons of paper per year, which uses only a small fraction of this cellulose.
Even though this seems small compared to total production, it still causes major deforestation and loss of vegetation, showing how human activities impact natural resources.

Q11. Describe the important properties of enzymes.
Answer: Enzymes are mostly proteins that act as biological catalysts. Their main properties are:

1. Catalytic action: They speed up reactions by millions of times.
2. Lowering activation energy: They make it easier for reactions to occur.
3. Optimum conditions: Each enzyme works best at a specific temperature and pH.
4. Substrate specificity: Each enzyme acts only on one type of substrate.
5. Active site: The substrate fits into a special pocket on the enzyme called the active site.
6. Cofactor requirement: Some enzymes need extra non-protein molecules like metal ions or vitamins to work properly.