Chapter 9: Biomolecules Short Questions | biology Class 11 CBSE

ByteNotes

Chapter 9: Biomolecules Short Questions | biology Class 11 CBSE | ByteNotes.in

Short Answer

Medium difficulty • Direct answer format

Medium

Question 1

Quick Recall

What is the significance of the acid-soluble pool in the chemical analysis of living tissues?

The acid-soluble pool, obtained as the filtrate after grinding living tissue in trichloroacetic acid, contains thousands of small organic compounds with molecular weights ranging from 18 to approximately 800 daltons.
It represents roughly the cytoplasmic composition of the cell and includes biomolecules such as amino acids, sugars, fatty acids, nucleotides, and nucleosides.
Inorganic compounds like sulphate and phosphate are also found in the acid-soluble fraction, making it useful for analysing both organic and inorganic constituents of living tissues.

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 2

Quick Recall

Distinguish between a nucleoside and a nucleotide with one example of each.

A nucleoside consists of a nitrogenous base attached to a pentose sugar but lacks a phosphate group; examples include adenosine (adenine + ribose) and uridine (uracil + ribose).
A nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group esterified to the sugar; examples include adenylic acid and thymidylic acid.
Nucleotides are the building blocks of nucleic acids (DNA and RNA), while nucleosides are intermediates that become nucleotides upon addition of a phosphate group.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 3

Quick Recall

Why are lipids classified under the macromolecular (acid-insoluble) fraction despite having molecular weights below 800 Da?

Lipids are indeed small molecular weight compounds but they are arranged into membrane structures such as the cell membrane and other organelle membranes within the cell.
When living tissue is ground during analysis, these membranes break into small vesicles that are not water-soluble and therefore cannot pass through the filtration step.
These membrane vesicles thus co-sediment with the acid-insoluble fraction along with true macromolecules, even though lipids are not strictly macromolecules.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 4

Quick Recall

What is a zwitterion? Under what pH condition is an amino acid found in this form?

A zwitterion (also written as zwitterionic form) is the dipolar ionic form of an amino acid in which the amino group (–NH2) is protonated to –NH3+ and the carboxyl group (–COOH) is deprotonated to –COO–.
This form is represented as form B in the ionisation equilibrium of amino acids and carries both a positive and a negative charge simultaneously, making it electrically neutral overall.
The zwitterionic form exists at an intermediate pH (near the isoelectric point of the amino acid), where the net charge on the molecule is zero.

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 5

Quick Recall

Differentiate between saturated and unsaturated fatty acids with an example for each.

Saturated fatty acids contain no carbon-carbon double bonds (C=C) in their hydrocarbon chain; an example is palmitic acid, which has 16 carbon atoms including the carboxyl carbon.
Unsaturated fatty acids contain one or more C=C double bonds in their hydrocarbon chain; arachidonic acid (20 carbon atoms) is an example of a polyunsaturated fatty acid.
Saturated fatty acids generally have higher melting points and are solid or semi-solid at room temperature, while unsaturated fatty acids have lower melting points and tend to remain liquid (oils).

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 6

Quick Recall

Give two differences between primary and secondary metabolites found in living organisms.

Primary metabolites such as amino acids, sugars, and nucleotides are found in all living cells and have identifiable, well-known functions in normal physiological processes like growth, energy production, and reproduction.
Secondary metabolites such as alkaloids, flavonoids, rubber, essential oils, and antibiotics are found mainly in plants, fungi, and microbial cells, and their roles in the host organism are not always fully understood.
Many secondary metabolites are of great use to human welfare (e.g., drugs, spices, scents, pigments) and some have ecological importance, distinguishing them from the universally essential primary metabolites.

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 7

Quick Recall

What is the primary structure of a protein and how is it represented?

The primary structure of a protein refers to the sequence of amino acids, i.e., the positional information specifying which amino acid occupies each position along the polypeptide chain.
A protein is imagined as a line with the left end representing the first amino acid (called the N-terminal amino acid) and the right end representing the last amino acid (called the C-terminal amino acid).
The primary structure is the most fundamental level of protein organisation and serves as the basis for determining all higher levels of structure (secondary, tertiary, and quaternary).

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 8

Quick Recall

State the role of the active site in enzyme catalysis.

The active site is a crevice or pocket formed in the three-dimensional (tertiary) structure of the enzyme where the polypeptide chain criss-crosses upon itself, creating a specifically shaped binding region.
The substrate molecule fits into the active site, forming an enzyme-substrate (ES) complex; this binding induces the enzyme to alter its shape to fit more tightly around the substrate.
The active site brings the substrate into a transition state by breaking and forming chemical bonds, ultimately converting the substrate into product(s) before releasing them and regenerating the free enzyme.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 9

Quick Recall

Name the most abundant protein in (a) the animal world and (b) the entire biosphere, and state the function of each.

The most abundant protein in the animal world is collagen, which serves as the intercellular ground substance, providing structural support and strength to connective tissues.
The most abundant protein in the whole biosphere is Ribulose bisphosphate Carboxylase-Oxygenase (RuBisCO), which is involved in the fixation of carbon dioxide during photosynthesis.
Both proteins highlight the enormous diversity of protein function — collagen as a structural protein and RuBisCO as a catalytic enzyme — reflecting the versatility of protein molecules.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 10

Quick Recall

Why is the tertiary structure of a protein considered absolutely necessary for its biological activity?

The tertiary structure is the overall three-dimensional conformation of the polypeptide chain folded upon itself, resembling a hollow woolen ball, and it is at this level that the active site of an enzyme (or the binding site of other proteins) is formed.
Without the tertiary structure, the functional regions of the protein such as the active site or receptor-binding site cannot adopt the correct shape, making the protein unable to interact with its specific ligand, substrate, or binding partner.
High temperatures disrupt the tertiary structure (denaturation), which destroys biological activity, demonstrating that three-dimensional conformation — not just amino acid sequence — is essential for protein function.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 11

Quick Recall

Differentiate between purines and pyrimidines found in nucleic acids with examples.

Purines are nitrogenous bases with a double-ring heterocyclic structure (a purine ring); adenine and guanine are the two purines found in nucleic acids.
Pyrimidines are nitrogenous bases with a single-ring heterocyclic structure (a pyrimidine ring); cytosine, uracil, and thymine are the pyrimidines found in nucleic acids.
In DNA, adenine pairs with thymine and guanine pairs with cytosine; in RNA, uracil replaces thymine as the base that pairs with adenine.

ByteNotes

Short Answer

Medium difficulty • Direct answer format

Medium

Question 12

Quick Recall

What is a competitive inhibitor? Give one example from the chapter.

A competitive inhibitor is a chemical that closely resembles the substrate of an enzyme in its molecular structure and competes with the substrate for binding to the active site of the enzyme.
Because the inhibitor occupies the active site, the actual substrate cannot bind, resulting in a decline in enzyme activity; this inhibition can potentially be overcome by increasing substrate concentration.
An example given in the chapter is the inhibition of the enzyme succinic dehydrogenase by malonate, which closely resembles the substrate succinate in structure; such competitive inhibitors are used in controlling bacterial pathogens.

ByteNotes

Short Answer

Easy difficulty • Direct answer format

Easy

Question 13

Quick Recall

What are phospholipids? State their location and give one example.

Phospholipids are a class of lipids that contain glycerol and fatty acids (like other lipids) but additionally have a phosphorous atom and a phosphorylated organic compound attached to the glycerol backbone.
They are found in cell membranes (and other biological membranes), where they form the lipid bilayer that constitutes the basic structural framework of all cellular membranes.
Lecithin is an example of a phospholipid; neural tissues in particular have lipids with more complex structures than simple phospholipids.

ByteNotes

Premium Access

Unlock all Short Questions

You are viewing 13 free short questions from this chapter. Upgrade to Premium to unlock the remaining 12 questions.

Upgrade to Premium12 questions locked

Chapter sections

Chapter 9: Biomolecules | Short Questions

What is the significance of the acid-soluble pool in the chemical analysis of living tissues?

Distinguish between a nucleoside and a nucleotide with one example of each.

Why are lipids classified under the macromolecular (acid-insoluble) fraction despite having molecular weights below 800 Da?

What is a zwitterion? Under what pH condition is an amino acid found in this form?

Differentiate between saturated and unsaturated fatty acids with an example for each.

Give two differences between primary and secondary metabolites found in living organisms.

What is the primary structure of a protein and how is it represented?

State the role of the active site in enzyme catalysis.

Name the most abundant protein in (a) the animal world and (b) the entire biosphere, and state the function of each.

Why is the tertiary structure of a protein considered absolutely necessary for its biological activity?

Differentiate between purines and pyrimidines found in nucleic acids with examples.

What is a competitive inhibitor? Give one example from the chapter.

What are phospholipids? State their location and give one example.

Unlock all Short Questions