The breakdown of glucose in cytoplasm results in the formation of
- A.pyruvate and energy
- B.pyruvate and carbon dioxide
- C.pyruvate and oxygen
- D.pyruvate and nitrogen
Correct answer
Explanation
The correct answer is A, pyruvate and energy. In the cytoplasm, glucose is split by glycolysis into two molecules of pyruvate, releasing a small amount of energy as ATP.
Glycolysis is the first step of respiration in all living cells and needs no oxygen. One six-carbon glucose molecule is broken into two three-carbon pyruvate molecules, with a net gain of two ATP and two NADH. What happens next depends on oxygen: with oxygen, pyruvate enters the mitochondria and is fully broken down into carbon dioxide and water, giving much more energy; without it, pyruvate becomes lactic acid in muscles or ethanol and carbon dioxide in yeast.
B is wrong because carbon dioxide is not released in glycolysis; it is given off later in the mitochondria or during fermentation in yeast.
C is wrong because respiration uses oxygen; it does not produce it.
D is wrong because glucose contains no nitrogen, so nitrogen cannot be formed from it.
Exam tip: glycolysis – cytoplasm, glucose to 2 pyruvate, net 2 ATP, no oxygen needed.
Practice Questions
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- A.Alpha and Beta radiations only
- B.Alpha and Gamma radiations only
- C.Beta and Gamma radiations only
- D.Alpha, Beta and Gamma radiations
Show answer
Neither beta nor gamma emission changes the total number of protons and neutrons in a nucleus, so the mass number stays the same.
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- B.Facilitated transport is an example of active transport.
- C.Water moves across plasma membrane by active transport.
- D.Facilitated transport requires assistance of carrier proteins.
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- A.Richard Feynman
- B.Murray Gell-Mann
- C.Albert Einstein
- D.Niels Bohr
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- A.Kinetochore
- B.Chromonema
- C.Telomere
- D.Centriole
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Read the full explanation →Which one of the following is the chemical name of heavy water?
- A.Hydrogen oxide
- B.Deuterium dioxide
- C.Deuterium oxide
- D.Heavy hydrogen oxide
Show answer
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