Free Biological Molecules MCQs with Answers
1,790 Biological Molecules MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
The chapter covers water's polarity and biological roles, carbohydrates, lipids, proteins and nucleic acids, including their monomers, bonds, structures and functions. It also distinguishes RNA from DNA and explains conjugated molecules such as glycoproteins, glycolipids and nucleoproteins, which combine organic molecules with a non-protein component.
Last updated
1,790 questions · page 1 of 90
- A. Its low surface tension
- B. Its high specific heat capacity
- C. Its low density in the liquid state
- D. Its inability to form hydrogen bonds
Explanation: Water has an unusually high specific heat capacity because a large amount of energy is absorbed breaking hydrogen bonds before the…
Correct answer: Its high specific heat capacity- A. non-polar
- B. polar
- C. ionised at all temperatures
- D. held together by covalent bonds between molecules
Explanation: The oxygen atom pulls the shared electrons away from the two hydrogens, leaving a partial negative charge on the oxygen and partial…
Correct answer: polar- A. Hydrolysis
- B. Condensation
- C. Oxidation
- D. Neutralisation
Explanation: A condensation reaction joins the two monosaccharides through a glycosidic linkage and releases one molecule of water.
Correct answer: Condensation- A. cellulose contains beta 1,4 linkages that human enzymes cannot hydrolyse
- B. cellulose molecules are too large to enter the gut
- C. cellulose is a protein rather than a carbohydrate
- D. starch contains no glycosidic bonds at all
Explanation: Starch is built from alpha glucose and its alpha 1,4 linkages are hydrolysed by amylase, while cellulose is built from beta glucose and…
Correct answer: cellulose contains beta 1,4 linkages that human enzymes cannot hydrolyse- A. Sucrose
- B. Starch
- C. Maltose
- D. Cellulose
Explanation: Maltose keeps a free anomeric carbon, so its open-chain form has an aldehyde group that reduces Benedict's reagent to a brick red…
Correct answer: Maltose- A. two amino groups
- B. the carboxyl group of one amino acid and the amino group of the next
- C. two R groups
- D. the carboxyl group of one amino acid and the R group of the next
Explanation: A peptide bond is a condensation between the carboxyl group of one amino acid and the alpha amino group of the next, releasing water.
Correct answer: the carboxyl group of one amino acid and the amino group of the next- A. primary structure
- B. secondary structure
- C. tertiary structure
- D. quaternary structure
Explanation: Secondary structure is the regular local folding held together by hydrogen bonds between the backbone carbonyl and amide groups, giving…
Correct answer: secondary structure- A. primary structure only
- B. secondary structure only
- C. tertiary structure only
- D. quaternary structure
Explanation: Quaternary structure exists whenever a functional protein is built from more than one polypeptide chain.
Correct answer: quaternary structure- A. contain more oxygen atoms per carbon
- B. are more highly reduced, with more carbon-hydrogen bonds per gram
- C. are soluble in water
- D. are broken down without any oxygen
Explanation: Energy is released when carbon-hydrogen bonds are oxidised, and a fatty acid chain is almost entirely carbon and hydrogen with very little…
Correct answer: are more highly reduced, with more carbon-hydrogen bonds per gram- A. two hydrophobic ends
- B. a hydrophilic head and hydrophobic tails
- C. two hydrophilic ends
- D. no charged groups at all
Explanation: The phosphate head is charged and interacts with water, while the two fatty acid tails are non-polar and are excluded from it.
Correct answer: a hydrophilic head and hydrophobic tails- A. It contains thymine in place of uracil
- B. It contains ribose and is usually single stranded
- C. It is always double stranded like DNA
- D. It contains deoxyribose and uracil
Explanation: RNA carries ribose, which has a hydroxyl group at carbon 2, and it is normally a single strand that can fold back on itself, as tRNA does…
Correct answer: It contains ribose and is usually single stranded- A. one hydrogen bond
- B. two hydrogen bonds
- C. three hydrogen bonds
- D. a covalent bond
Explanation: Adenine and thymine are held together by two hydrogen bonds, while guanine and cytosine are held by three.
Correct answer: two hydrogen bonds- A. 22%
- B. 28%
- C. 44%
- D. 56%
Explanation: Chargaff's rule applies to the double stranded molecule, so A equals T and G equals C.
Correct answer: 28%- A. they carry identical base sequences
- B. one runs 5' to 3' while the other runs 3' to 5'
- C. they are held together by covalent bonds
- D. they coil in opposite directions around each other
Explanation: Antiparallel refers to the direction of the sugar-phosphate backbones: one strand runs 5' to 3' while its partner runs 3' to 5'.
Correct answer: one runs 5' to 3' while the other runs 3' to 5'- A. two identical monomers joined together
- B. a protein combined with a non-protein group
- C. a lipid combined with another lipid
- D. a polysaccharide broken into monosaccharides
Explanation: Conjugated molecules are built from two different classes of biological molecule joined together, so a glycoprotein is protein plus…
Correct answer: a protein combined with a non-protein group16. Which class of organic molecule forms the greatest proportion of the dry mass of a typical cell?
- A. Carbohydrates
- B. Proteins
- C. Lipids
- D. Nucleic acids
Explanation: Proteins account for roughly half the dry mass because they serve as enzymes, transporters, receptors, antibodies and structural fibres…
Correct answer: Proteins- A. Starch
- B. Glycogen
- C. Glucose
- D. Cellulose
Explanation: Glucose is a monosaccharide, a single small unit and therefore a micromolecule, while the other three are polysaccharides built from…
Correct answer: Glucose- A. carbon, hydrogen, oxygen and nitrogen
- B. carbon, hydrogen, oxygen and sulphur
- C. sodium, potassium, calcium and chlorine
- D. carbon, nitrogen, phosphorus and sulphur
Explanation: Carbon, hydrogen, oxygen and nitrogen are the backbone of carbohydrates, lipids, proteins and nucleic acids, with phosphorus and sulphur…
Correct answer: carbon, hydrogen, oxygen and nitrogen- A. an amino acid
- B. a monosaccharide
- C. a nucleotide
- D. a fatty acid
Explanation: Each nucleotide consists of a pentose sugar, a phosphate group and a nitrogenous base, and successive nucleotides are linked by…
Correct answer: a nucleotide- A. about 10 per cent
- B. about 30 per cent
- C. about 50 per cent
- D. 70 to 90 per cent
Explanation: Most cells are between seventy and ninety per cent water, which is why it is treated as the medium of life rather than as one nutrient…
Correct answer: 70 to 90 per centBiological Molecules MCQs: common questions
Are these Biological Molecules MCQs free?
Yes. All Biological Molecules MCQs from Biology are free on TestUstad, with unlimited attempts and no account needed. Nothing on this page is a sample or a trial.
How many Biological Molecules MCQs are on this page?
There are 1,790 Biological Molecules MCQs in the Biology bank, shown 20 to a page with the correct answer and an explanation on each.
Does every Biological Molecules MCQ have an explanation?
Yes. Each Biological Molecules question shows the correct option and a written explanation of why it is correct, so a wrong answer teaches you something rather than just being marked wrong.
Can I take a timed Biological Molecules test?
Yes. The practice button on this page starts a free Biological Molecules test drawn from the Biology bank. It marks each answer instantly, gives you a score at the end, and can be retaken as many times as you like.