49 practice MCQs on photosynthesis, cellular respiration, ATP, glycolysis, the Krebs cycle and the electron transport chain. Every question has the correct answer and an explanation.
Start free — 20 questionsBioenergetics is part of the MDCAT Biology syllabus. This page collects Bioenergetics MCQs in the style of past MDCAT papers — below are 12 of them with answers and explanations, and the full set of 49 questions is in the HighYield MDCAT QBank.
This chapter covers: photosynthesis, cellular respiration, ATP, glycolysis, the Krebs cycle and the electron transport chain.
Correct answer: A. Cristae
Cristae are the finger-like folds of the inner mitochondrial membrane that increase surface area for oxidative phosphorylation.
Correct answer: B. Mitochondria
Mitochondria are the organelles responsible for synthesizing ATP through cellular respiration and oxidative phosphorylation.
Correct answer: D. Acetic Acid
Before entering the Krebs cycle, pyruvate is decarboxylated and oxidized to acetic acid (as acetyl-CoA), releasing CO2.
Correct answer: D. Pyruvate
Pyruvate is the end product of glycolysis, formed from the breakdown of one molecule of glucose into two three-carbon pyruvate molecules.
Correct answer: B. Porphyrin ring
The porphyrin ring (head) of the chlorophyll molecule, containing a magnesium ion, is the light-absorbing part.
Correct answer: A. Acetic acid (active)
Pyruvate moves into the mitochondrial matrix, where it is oxidized to acetic acid (bound as acetyl-CoA), releasing CO2 as a by-product.
Correct answer: D. Co-enzyme Q
Electrons from both NADH and FADH2 are passed into the electron transport chain via coenzyme Q (ubiquinone).
Correct answer: A. —CH3
The functional (side) group of chlorophyll a is a methyl group (-CH3), distinguishing it from chlorophyll b, which has an aldehyde (-CHO) group instead.
Correct answer: B. Yellowish green
Chlorophyll-b is a secondary pigment that absorbs light primarily in the blue and red-orange wavelengths, giving it a yellowish-green colour.
Correct answer: C. 32
Out of the 36 ATPs that can potentially be generated through oxidative phosphorylation and the electron transport chain, approximately **32** ATPs are produced. The precise number can vary depending on specific factors and conditions, but 32 ATPs is a commonly cited estimate for the net ATP yield in eukaryotic cells during cellular respiration.
Correct answer: C. Methyl group on second pyrrole ring
The statement "Methyl group on the second pyrrole ring" in the context of chlorophyll a is correct.The presence of a methyl group on the second pyrrole ring is a correct part of the chlorophyll structure and plays a role in its overall function in photosynthesis.
Correct answer: C. Mature RBC's
Option C is correct.Mitochondria are usually absent in mature RBC's. Mature RBC's, or erythrocytes, are the most abundant type of blood cell. They are responsible for transporting oxygen from the lungs to the tissues of the body. Mature RBC's are also responsible for removing carbon dioxide from the tissues and transporting it back to the lungs. Mature RBC's do not have mitochondria because they do not need to produce their own energy. They obtain the energy they need from the glucose that is present in the blood. The other options all have mitochondria: Muscle cells: Mitochondria are essential for muscle cells because they provide the energy needed for muscle contraction. Cardiac cells: Cardiac cells, or heart muscle cells, also have mitochondria because they need a lot of energy to pump blood throughout the body. WBC's: WBC's, or white blood cells, have mitochondria because they need energy to fight infection and protect the body from disease
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