Free Cellular Respiration MCQs with Answers

• A. matrix of the mitochondrion
• B. inner mitochondrial membrane
• C. cytoplasm
• D. nucleus

Explanation: Every enzyme of glycolysis is dissolved in the cytosol, which is why the pathway runs in prokaryotes and in red blood cells that have no…

• A. 2
• B. 4
• C. 36
• D. 38

Explanation: Four ATP are made by substrate level phosphorylation but two were invested earlier to phosphorylate glucose and fructose 6 phosphate, so…

• A. lactic acid
• B. pyruvic acid
• C. acetyl CoA
• D. citric acid

Explanation: Glycolysis splits the six carbon glucose into two three carbon molecules of pyruvic acid, and what happens next depends on whether oxygen…

• A. cytoplasm
• B. intermembrane space of the mitochondrion
• C. smooth endoplasmic reticulum
• D. matrix of the mitochondrion

Explanation: Pyruvate is carried across both mitochondrial membranes and is then acted on by the pyruvate dehydrogenase complex in the matrix, which…

• A. citric acid
• B. oxaloacetic acid
• C. succinic acid
• D. malic acid

Explanation: The two carbon acetyl group is transferred to the four carbon oxaloacetic acid to give the six carbon citric acid, which is why the…

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: One turn yields three NADH, one FADH2, one ATP by substrate level phosphorylation and two molecules of carbon dioxide.

• A. water
• B. carbon dioxide
• C. molecular oxygen
• D. NAD

Explanation: Oxygen takes the electrons at the end of the chain and combines with protons to form metabolic water, which is why respiration stops…

• A. electrons are transferred directly to ADP
• B. protons flow back into the matrix through ATP synthase
• C. NADH transfers a phosphate group to ADP
• D. oxygen binds to ADP in the matrix

Explanation: Electron transport pumps protons out of the matrix into the intermembrane space, creating an electrochemical gradient, and the energy…

• A. cristae
• B. matrix
• C. thylakoids
• D. grana

Explanation: Cristae greatly increase the area available for the electron transport chain and the ATP synthase particles, so cells with a high energy…

• A. lactic acid and a large quantity of ATP
• B. ethanol and carbon dioxide
• C. acetyl CoA and water
• D. pyruvic acid and oxygen

Explanation: Yeast decarboxylates pyruvate to ethanal and then reduces it to ethanol, releasing carbon dioxide, which is the basis of both brewing and…

• A. regenerate NAD so that glycolysis can continue
• B. produce a large amount of ATP directly
• C. remove carbon dioxide from the cell
• D. activate the enzymes of the Krebs cycle

Explanation: Glycolysis needs a constant supply of oxidised NAD, and without oxygen the electron transport chain cannot regenerate it, so reducing…

• A. 2
• B. 4
• C. 12
• D. 38

Explanation: Two ATP come from glycolysis, two from the two turns of the Krebs cycle and the remainder from oxidative phosphorylation of the ten NADH…

• A. the link reaction
• B. the Krebs cycle
• C. glycolysis
• D. alcoholic fermentation

Explanation: Glycolysis only rearranges and splits the six carbons of glucose into two three carbon pyruvate molecules, so no carbon is lost as gas.

• A. inner mitochondrial membrane
• B. outer mitochondrial membrane
• C. mitochondrial matrix
• D. cytosol

Explanation: The cytochromes and other carriers are embedded in the inner membrane, whose folding into cristae provides the surface area, and the same…

• A. FADH2 carries fewer electrons than NADH
• B. FADH2 is produced only in the cytoplasm
• C. FADH2 is never reoxidised
• D. FADH2 delivers its electrons at a later point in the chain, so fewer protons are pumped

Explanation: Both carriers deliver a pair of electrons, but FADH2 feeds them in past the first proton pumping complex, so one fewer pump operates and…

• A. glycolysis at the phosphofructokinase step
• B. the ATP synthase channel
• C. cytochrome oxidase, the last carrier of the electron transport chain
• D. the Krebs cycle at citrate synthase

Explanation: Cyanide binds the iron of cytochrome oxidase, so electrons can no longer be passed to oxygen, the whole chain backs up and oxidative…

• A. oxidative phosphorylation
• B. substrate level phosphorylation
• C. photophosphorylation
• D. chemiosmosis

Explanation: This is how ATP is made twice in glycolysis and once per turn of the Krebs cycle, and it needs no membrane, no oxygen and no proton…

• A. excreted unchanged in the urine
• B. converted back to glucose within the muscle fibre itself
• C. completely oxidised in the muscle within seconds
• D. carried in the blood to the liver and reconverted to glucose

Explanation: Muscle lacks the enzymes to run gluconeogenesis, so lactate diffuses into the blood and the liver rebuilds it into glucose in the Cori…

• A. Fat
• B. Carbohydrate
• C. Protein
• D. Nucleic acid

Explanation: Fat yields roughly 9 kcal per gram against about 4 for carbohydrate and protein, because its carbon atoms are far more reduced and so give…

• A. They are bounded by a single membrane
• B. They contain digestive enzymes like a lysosome
• C. They carry 80S ribosomes identical to those of the cytoplasm
• D. They contain circular DNA and 70S ribosomes and divide by binary fission

Explanation: Circular DNA, 70S ribosomes and division by fission are all bacterial characteristics, and they are exactly what the endosymbiotic theory…