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Chapter 6· Biomolecules
MCQs with Answers Try each one first: tap an option to check it, then read the reasoning and why the others are wrong.
A note about the questions
The wording follows published solved exercises and every answer was re-checked by hand, so the wording or the order of options may differ slightly from your print.
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Set A: Textbook exercise 11 MCQs The multiple-choice questions at the end of Chapter 6 in your book, in the book's option order.
Q6.1 Carbohydrates
What is the primary function of carbohydrates?
(a) Provide energy (b) Act as enzymes (c) Regulate processes (d) Make membranes Show answer and reasoning Answer (a) Provide energy
Step by step
Enzymes are proteins; membranes are mainly lipids and proteins. Why the others are wrong
(b) enzymes are proteins.(c) hormones (proteins, steroids) regulate.(d) membranes are made of lipids and proteins.Q6.2 Carbohydrates
How will you differentiate between monosaccharides and polysaccharides?
(a) Monosaccharides are single sugars. (b) Polysaccharides are sweet in taste. (c) Monosaccharides are present in plant cell wall. (d) Polysaccharides dissolve easily. Show answer and reasoning Answer (a) Monosaccharides are single sugars.
Step by step
Mono = one sugar unit; poly = many. Why the others are wrong
(b) polysaccharides are tasteless.(c) the cell wall has cellulose, a polysaccharide.(d) polysaccharides are insoluble in water.Q6.3 Carbohydrates
What is true about cellulose?
(a) It is sweet in taste. (b) It is digestible by human digestive system. (c) It provides structural support in plants. (d) It is soluble in water. Show answer and reasoning Answer (c) It provides structural support in plants.
Step by step
Cellulose is a polysaccharide: tasteless and insoluble. Humans cannot digest it; it is dietary fibre. Why the others are wrong
(a) polysaccharides are tasteless.(b) it is undigestible dietary fibre.(d) insoluble in water.Remember
Cellulose = cell wall = support.
Q6.4 Proteins
Which of the following proteins is involved in oxygen transport?
(a) Insulin (b) Haemoglobin (c) Collagen (d) Keratin Show answer and reasoning Answer (b) Haemoglobin
Step by step
Insulin is a hormone; collagen and keratin are structural proteins. Why the others are wrong
(a) a hormone (51 amino acids).(c) structural (cartilage).(d) structural (hair, nails).Remember
Haem-o-globin carries O₂.
Q6.5 Proteins
Which component of an amino acid determines its unique properties?
(a) Amino group (b) Carboxyl group (c) R group (side group) (d) Hydrogen group Show answer and reasoning Answer (c) R group (side group)
Step by step
Amino, carboxyl and hydrogen are common to all amino acids. So the R group makes each one different. Why the others are wrong
(a) same in every amino acid.(b) same in every amino acid.(d) same in every amino acid.Remember
R = the "real" difference.
Q6.6 Proteins
Which proteins are involved in defence against pathogens?
(a) Antibodies (b) Myosin (c) Fibrinogen (d) Haemoglobin Show answer and reasoning Answer (a) Antibodies
Step by step
Myosin: muscle contraction. Fibrin(ogen): clotting. Haemoglobin: oxygen. Why the others are wrong
(b) muscle protein.(c) clotting protein (precursor of fibrin).(d) carries oxygen.Remember
Anti-bodies fight bodies (germs).
Q6.7 Lipids
Which of the following are the unit structures of lipids?
(a) Amino acids (b) Fatty acids and glycerol (c) Nucleotides (d) Simple sugars Show answer and reasoning Answer (b) Fatty acids and glycerol
Step by step
Amino acids → proteins; nucleotides → nucleic acids; simple sugars → carbohydrates. Why the others are wrong
(a) units of proteins.(c) units of nucleic acids.(d) units of carbohydrates.Remember
Fat = glycerol + fatty acids.
Q6.8 Lipids
How do unsaturated fatty acids differ from saturated fatty acids?
(a) They have more hydrogen atoms. (b) They contain double bonds in their hydrocarbon chains. (c) They are solid at room temperature. (d) They are found only in animal fats. Show answer and reasoning Answer (b) They contain double bonds in their hydrocarbon chains.
Step by step
Saturated = maximum hydrogen, no double bond, solid. Unsaturated = double bond(s), fewer H, liquid (plant oils). Why the others are wrong
(a) they have fewer hydrogen atoms.(c) they are liquid (oils).(d) plant oils are unsaturated.Remember
Un-saturated = un-filled with H = double bond.
Q6.9 Proteins
Which of the following is NOT a function of proteins?
(a) Transport oxygen in the blood. (b) Carry genetic information. (c) Help in digesting food. (d) Fight against pathogens. Show answer and reasoning Answer (b) Carry genetic information.
Step by step
Genetic information is in the sequence of nucleotides of DNA. Why the others are wrong
(a) haemoglobin does it.(c) digestive enzymes are proteins.(d) antibodies do it.Remember
Genes = DNA, not protein.
Q6.10 Nucleic Acids
Which components make up a nucleotide?
(a) Sugar, phosphate, nitrogenous base (b) Amino acid, sugar, nitrogenous base (c) Fatty acid, phosphate, nitrogenous base (d) Protein, sugar, nitrogenous base Show answer and reasoning Answer (a) Sugar, phosphate, nitrogenous base
Step by step
No amino acid, fatty acid or protein is part of a nucleotide. Why the others are wrong
(b) no amino acid.(c) no fatty acid.(d) no protein.Remember
Nucleotide = S-P-B (Sugar, Phosphate, Base).
Q6.11 Nucleic Acids
Which nitrogenous base is found in RNA but not in DNA?
(a) Adenine (b) Thymine (c) Uracil (d) Guanine Show answer and reasoning Answer (c) Uracil
Step by step
A, C, G are in both. T only in DNA; U only in RNA. Why the others are wrong
(a) in both.(b) in DNA only.(d) in both.Remember
U for RNA (rib-U-se... U-racil).
Set B: More MCQs from this chapter 13 MCQs Extra questions on the same ideas, of the kind set in board papers and class tests.
QB1 Biomolecules
The study of the chemical processes that occur within living organisms is called:
(a) Molecular biology (b) Biophysics (c) Cytology (d) Biochemistry Show answer and reasoning Answer (d) Biochemistry
Step by step
Processes → biochemistry; molecules' structure and function → molecular biology. Why the others are wrong
(a) structure and function of biomolecules.(b) physics of living things.(c) study of cells.Remember
Bio + chemistry = chemical processes in life.
QB2 Biomolecules
Proteins make up what percentage of the dry mass of protoplasm?
(a) 18 % (b) 15 % (c) 10 % (d) 50 % Show answer and reasoning Answer (d) 50 %
Step by step
50 + 18 + 15 + 10 = 93 %. Why the others are wrong
(a) nucleic acids.(b) carbohydrates.(c) lipids.QB3 Carbohydrates
The general formula of carbohydrates is:
(a) CₙH₂ₙ (b) Cₙ(H₂O)₂ₙ (c) Cₙ(H₂O)ₙ (d) CₙH₂ₙ₊₂ Show answer and reasoning Answer (c) Cₙ(H₂O)ₙ
Step by step
Glucose C₆H₁₂O₆ = C₆(H₂O)₆. Why the others are wrong
(a) that is an alkene (no oxygen).(b) too much water.(d) that is an alkane.Remember
Carbo-HYDRATE = carbon + water.
QB4 Carbohydrates
Sucrose (table sugar) is made of:
(a) two glucose molecules (b) glucose and galactose (c) two fructose molecules (d) glucose and fructose Show answer and reasoning Answer (d) glucose and fructose
Step by step
Glucose + glucose = maltose; glucose + galactose = lactose (milk sugar). Why the others are wrong
(a) that is maltose.(b) that is lactose.(c) no such common sugar.Remember
Sucrose = sugar cane = glucose + fructose.
QB5 Carbohydrates
The animal starch mainly stored in liver and muscles is:
(a) starch (b) cellulose (c) glycogen (d) chitin Show answer and reasoning Answer (c) glycogen
Step by step
Starch: plant storage; cellulose: plant cell wall; chitin: insect skeleton, fungal wall. Why the others are wrong
(a) stored in plants.(b) plant cell walls.(d) exoskeletons and fungal walls.Remember
Glyco-GEN = animal "energy GENerator" store.
QB6 Carbohydrates
Chitin is found in:
(a) the cell walls of plants (b) liver and muscles (c) milk and dairy products (d) exoskeletons of insects and cell walls of fungi Show answer and reasoning Answer (d) exoskeletons of insects and cell walls of fungi
Step by step
Plant walls: cellulose. Liver and muscles: glycogen. Milk: lactose. Why the others are wrong
(a) cellulose.(b) glycogen.(c) lactose.Remember
Chitin = crab shell.
QB7 Proteins
Insulin protein has how many amino acids?
Show answer and reasoning Answer (a) 51
Step by step
574 = haemoglobin; 20 = types used in most proteins; 170 = types found in organisms. Why the others are wrong
(b) haemoglobin.(c) types of amino acids in most proteins.(d) types of amino acids in organisms.Remember
Insulin 51, haemoglobin 574.
QB8 Proteins
Amino acids that cannot be synthesized by our body and are supplied by foods are called essential amino acids. Their number is:
Show answer and reasoning Answer (b) 9
Step by step
9 essential + 11 non-essential = 20. Why the others are wrong
(a) non-essential.(c) the total.(d) types in organisms.Remember
9 from food, 11 home-made.
QB9 Lipids
A phospholipid molecule consists of:
(a) one glycerol and three fatty acids (b) one glycerol, two fatty acids and a phosphate group (c) three glycerols and one fatty acid (d) one fatty acid and two phosphate groups Show answer and reasoning Answer (b) one glycerol, two fatty acids and a phosphate group
Step by step
Replace one fatty acid of a fat with a phosphate group → phospholipid. Why the others are wrong
(a) that is a fat or oil.(c) Wrong.(d) Wrong.Remember
Phospho-lipid: one P swaps one fatty acid.
QB10 Lipids
Steroid hormones are derived from which lipid?
(a) Glycerol (b) Phospholipid (c) Cholesterol (d) Unsaturated fatty acid Show answer and reasoning Answer (c) Cholesterol
Step by step
Lipid functions: energy reserve, membranes, insulation, hormones, absorbing vitamins A, D, E, K. Why the others are wrong
(a) a part of fats.(b) makes membranes.(d) part of oils.Remember
Steroids from cholesterol.
QB11 Nucleic Acids
How many hydrogen bonds are present between cytosine and guanine?
(a) One (b) Two (c) Four (d) Three Show answer and reasoning Answer (d) Three
Step by step
A=T (2), C≡G (3). Why the others are wrong
(a) Wrong.(b) that is A–T.(c) Wrong.Remember
AT = 2 letters, 2 bonds; CG is "Cee-Gee" with 3 bonds.
QB12 Nucleic Acids
The function of transfer RNA (tRNA) is to:
(a) carry the genetic information from DNA to ribosomes (b) make the structure of ribosomes (c) copy the sequence of DNA (d) transfer specific amino acids to the ribosomes Show answer and reasoning Answer (d) transfer specific amino acids to the ribosomes
Step by step
mRNA carries the message; rRNA builds ribosomes; tRNA brings amino acids. Why the others are wrong
(a) that is mRNA.(b) that is rRNA.(c) that is transcription (making mRNA).Remember
T-RNA = Transfer / Taxi for amino acids.
QB13 Working of DNA and RNA
The process of making an mRNA copy of DNA is called:
(a) transcription (b) translation (c) replication (d) mutation Show answer and reasoning Answer (a) transcription
Step by step
DNA → mRNA: transcription (in nucleus). mRNA → protein: translation (at ribosome). Why the others are wrong
(b) mRNA to protein.(c) copying DNA into DNA.(d) a change in DNA.Remember
Transcribe = copy in the same language (nucleotides).
