All Free Biology MCQs with Answers

• A. Ribosome
• B. Mitochondrion
• C. Golgi apparatus
• D. Lysosome

Explanation: The mitochondrion generates most of the cell’s ATP through aerobic respiration, earning it the name powerhouse of the cell.

• A. Liver
• B. Pancreas
• C. Thyroid gland
• D. Adrenal gland

Explanation: Insulin is produced by the beta cells of the islets of Langerhans in the pancreas, and it lowers blood glucose.

• 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…

• 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…

• 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.

• 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…

• 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…

• 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.

• 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…

• 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.

• 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…

• 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.

• 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…

• 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.

• 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.

• 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'.

• 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…

• A. Mitochondrion
• B. Cellulose cell wall
• C. Ribosome
• D. Golgi apparatus

Explanation: A cellulose cell wall lies outside the plasma membrane of every plant cell and gives it a fixed shape and resistance to bursting when…

• A. no ribosomes
• B. no membrane bound nucleus or organelles
• C. no genetic material
• D. no plasma membrane

Explanation: Prokaryotes keep their DNA in a nucleoid region with no surrounding envelope and have no mitochondria, endoplasmic reticulum or Golgi…

• A. 70S
• B. 80S
• C. 90S
• D. 60S

Explanation: Prokaryotic ribosomes are 70S, made of a 50S and a 30S subunit, while eukaryotic cytoplasmic ribosomes are 80S.