Free Classification of Biological Molecules MCQs with Answers

• A. form waterproof coatings on leaves, fruits and exoskeletons
• B. store more energy per gram than any other molecule
• C. build the phospholipid bilayer of membranes
• D. act as receptors for hormones

Explanation: Waxes are highly hydrophobic, so the cuticle on leaves and the wax layer on insect exoskeletons prevent water loss and resist wetting.

• A. are attracted to water molecules
• B. carry a strong negative charge
• C. are non polar and are excluded from the surrounding water
• D. are forced inwards by membrane proteins

Explanation: The hydrophobic tails avoid water while the polar phosphate heads face it, so the bilayer assembles itself with tails inside.

• A. Triglyceride
• B. Steroid
• C. Phospholipid
• D. Wax

Explanation: Steroids such as cholesterol and testosterone are built from four fused carbon rings and contain no fatty acid chains.

• A. cytoplasm
• B. ribosome itself
• C. Golgi apparatus
• D. nucleolus

Explanation: The nucleolus transcribes rRNA and assembles it with proteins into ribosomal subunits, which then leave through nuclear pores.

• A. messenger RNA
• B. transfer RNA
• C. ribosomal RNA
• D. DNA

Explanation: Each tRNA carries a three-base anticodon loop that base pairs with the complementary codon on mRNA, ensuring the correct amino acid is…

• A. ribose and uracil
• B. deoxyribose and thymine
• C. ribose and thymine
• D. deoxyribose and uracil

Explanation: RNA has the sugar ribose and uses uracil in place of thymine, pairing uracil with adenine.

• A. Amylose
• B. Palmitic acid
• C. Glycogen
• D. Glycolipid

Explanation: A conjugated molecule combines two different classes of biomolecule, here a carbohydrate with a lipid.

• A. substrate
• B. apoenzyme
• C. prosthetic group
• D. peptide

Explanation: A prosthetic group, such as the haem of haemoglobin, is a non protein part fixed tightly to the protein.

• A. energy storage for the cell
• B. cell recognition and signalling
• C. transport of oxygen
• D. replication of DNA

Explanation: The carbohydrate chains of glycolipids and glycoproteins act as identification markers, which is why blood group antigens sit on the red…

• A. the sugars bond only to purines
• B. phosphate groups pair with pyrimidines
• C. hydrogen bonds form only between bases of equal size
• D. each base pair contains one purine and one pyrimidine

Explanation: Adenine and guanine are the purines, thymine and cytosine the pyrimidines, and every pair across the helix matches one of each.

• A. alternating bases and phosphate groups
• B. bases only, stacked one above another
• C. alternating deoxyribose sugars and phosphate groups
• D. alternating sugars and bases

Explanation: Phosphodiester bonds link the sugar of one nucleotide to the phosphate of the next, making a repeating sugar phosphate rail with the bases…

• A. contains one old strand and one newly synthesised strand
• B. is built entirely from new nucleotides
• C. conserves only half of its original bases
• D. is rebuilt only in every second cell cycle

Explanation: When the two parental strands separate, each serves as a template for a new partner, so both daughter helices retain one original strand.

• A. adenine equals guanine and cytosine equals thymine
• B. the amount of adenine is always greater than that of thymine
• C. the amount of adenine equals thymine and guanine equals cytosine
• D. purines are always more numerous than pyrimidines

Explanation: Because A pairs with T and G pairs with C across the helix, their amounts must match in any double stranded DNA.

• A. Soil Science
• B. Agronomy
• C. Metrology
• D. Ecology

Explanation: Agronomy is the applied science of crop production, including the management of soil, crops and their productivity.

• A. Genetics
• B. Taxonomy
• C. Archeology
• D. Paleontology

Explanation: Taxonomy is the branch of biology concerned with identifying, naming and classifying organisms.

• A. 16 Bio-elements
• B. 12 Bio-elements
• C. 10 Bio-elements
• D. 6 Bio-elements

Explanation: About 99% of the human body's mass is contributed by six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

• A. Photosynthetic
• B. Chemosynthetic
• C. Completely parasitic
• D. Absorptive heterotrophs

Explanation: Fungi are absorptive heterotrophs: they secrete digestive enzymes onto food outside the body and absorb the soluble products.

• A. fucoxanthin
• B. phycocyanin
• C. phycoerythrin
• D. bilirubin

Explanation: Red algae contain the red phycobilin pigment phycoerythrin, which absorbs green and blue light and helps them photosynthesise at greater…

• A. carbon, oxygen, nitrogen, sulfur
• B. carbon, oxygen, hydrogen, nitrogen
• C. carbon, oxygen, sulfur, phosphorus
• D. carbon, sulfur, hydrogen, magnesium

Explanation: Carbon, hydrogen, oxygen and nitrogen are the four most abundant elements in living cells because they form carbohydrates, lipids…

• A. Polysaccharide
• B. Protein
• C. Hemoglobin
• D. ATP

Explanation: ATP is a relatively small molecule made from adenine, ribose, and three phosphate groups, and it transfers energy directly in cells.