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KCSE Biology — practice by topic

Browse 142 questions across 2 Biology topics. Choose what you want to revise, then open a question to check its answer and worked solution.

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Biology topics

Cellular Respiration (86)Photosynthesis (56)

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What happens to the potential energy of a compound when an electron is removed from it?Read the answer and worked solution →The principal electron carriers of cellular respiration are derivatives of nucleotides and come from which group of vitamins?Read the answer and worked solution →Why can a living cell not simply store large amounts of free energy inside itself?Read the answer and worked solution →What is the term for the removal of a phosphate group from a molecule?Read the answer and worked solution →

Worked practice questions

What happens to the potential energy of a compound when an electron is removed from it?

  1. Its potential energy decreases
  2. Its potential energy increases
  3. Its potential energy is unchanged
  4. Its potential energy is doubled
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Correct answer: A. Its potential energy decreases

1. Removing an electron from a molecule is oxidation. 2. Oxidation results in a decrease in potential energy in the oxidized compound. 3. The electron is not lost to the cytoplasm, it moves onto a second compound whose potential energy rises instead. 4. So the oxidized partner falls in energy while the reduced partner gains it, which rules out an unchanged value. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.1 Energy in Living Systems_

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The principal electron carriers of cellular respiration are derivatives of nucleotides and come from which group of vitamins?

  1. The vitamin K group
  2. The vitamin A group
  3. The vitamin C group
  4. The vitamin B group
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Correct answer: D. The vitamin B group

1. Electron carriers are small compounds that bind and shuttle high-energy electrons between compounds in pathways. 2. The principal carriers are derived from the B vitamin group and are derivatives of nucleotides. 3. Nicotinamide adenine dinucleotide comes from niacin, one of the B vitamins. 4. No carrier in this set is built from vitamin A, C or K. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.1 Energy in Living Systems_

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Why can a living cell not simply store large amounts of free energy inside itself?

  1. The heat produced would destroy the cell
  2. The energy would turn the cytoplasm acidic
  3. The energy would stop all enzymes forming
  4. The energy would leak out through the membrane
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Correct answer: A. The heat produced would destroy the cell

1. A living cell cannot store significant amounts of free energy. 2. Excess free energy would raise the heat inside the cell. 3. That heat drives excessive thermal motion, which damages and then destroys the cell. 4. The cell therefore holds energy in adenosine triphosphate and releases it only as needed. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.1 Energy in Living Systems_

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