OCR GCSE Biology B (Twenty First Century)
OCR GCSE Biology B B4.1 What happens during cellular respiration? Exam Questions
Free OCR GCSE Biology B exam questions for B4.1 What happens during cellular respiration?, with a mark scheme for every pack. Covers aerobic and anaerobic respiration, ATP, mitochondria, lactic acid, fermentation in yeast, comparing energy yields and investigating respiration rate.
B4.1 What happens during cellular respiration? exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About OCR GCSE Biology B B4.1 What happens during cellular respiration?
B4.1 opens chapter B4, Using Food and Controlling Growth, with cellular respiration, the process that releases energy from glucose in every living cell. You need equations for aerobic respiration and for anaerobic respiration in animals and in plants and yeast, and to explain why aerobic respiration releases far more energy. ATP as the energy carrier, the role of mitochondria and the uses of energy in cells are also included. This links back to photosynthesis in B3.1 and forward to exercise and body systems in B5. Examiners frequently ask you to compare the two types and analyse respirometer or yeast experiments.
What you need to know
- Aerobic respiration glucose + oxygen to carbon dioxide + water. Balanced: C6H12O6 + 6O2 to 6CO2 + 6H2O. It is exothermic and takes place mainly in mitochondria.
- ATP Respiration releases energy that is used to make ATP, which transfers energy to processes such as muscle contraction, active transport and building large molecules.
- Anaerobic respiration in animals When oxygen is in short supply, glucose is converted to lactic acid. Much less energy is released, and an oxygen debt builds up that must be repaid after exercise.
- Anaerobic respiration in plants and yeast glucose to ethanol + carbon dioxide. This is fermentation, used in brewing and bread making.
- Comparing types Aerobic respiration needs oxygen and fully breaks down glucose, releasing much more energy per glucose molecule than anaerobic respiration.
- Investigating respiration Rate can be measured by the volume of carbon dioxide released by yeast, or oxygen taken in by small organisms in a respirometer. Temperature affects rate because respiration is controlled by enzymes.
Common mistakes in B4.1 What happens during cellular respiration?
- Saying respiration makes energy. Energy is released or transferred, not made.
- Confusing respiration with breathing. Respiration is a chemical reaction in cells; breathing is moving air in and out of the lungs.
- Writing that plants do not respire. Plants respire all the time, day and night.
- Stating that anaerobic respiration in humans produces carbon dioxide or ethanol. In humans it produces only lactic acid.
- Saying lactic acid causes the oxygen debt. The oxygen debt is the extra oxygen needed to break down lactic acid after exercise.
Try three B4.1 What happens during cellular respiration? exam-style questions
1. Name the product of anaerobic respiration in human muscle cells. (1 mark)
Show the mark scheme answer
Lactic acid.
2. Yeast produced 18 cm3 of carbon dioxide in 6 minutes at 25 °C and 42 cm3 in 6 minutes at 35 °C. Calculate the percentage increase in volume. (2 marks)
Show the mark scheme answer
(42 minus 18) / 18 x 100; = 133%.
3. Explain why muscle cells contain many mitochondria. (3 marks)
Show the mark scheme answer
Mitochondria are where aerobic respiration takes place; muscles need lots of energy for contraction; so many mitochondria release more energy (ATP) by aerobic respiration.
B4.1 What happens during cellular respiration? FAQs
What does OCR GCSE Biology B B4.1 cover?
It covers aerobic and anaerobic respiration in animals, plants and yeast, ATP, mitochondria, the oxygen debt and practical investigations into respiration rate.
Which paper is B4.1 examined in?
J257 has two papers at each tier, Breadth in Biology and Depth in Biology, and content from any chapter, including B4, can be assessed on either one. Expect it to be linked to ideas about science and to other chapters.
Which equations do I need for B4.1?
Learn the word and balanced symbol equations for aerobic respiration, plus word equations for anaerobic respiration in muscles (to lactic acid) and in yeast and plants (to ethanol and carbon dioxide).
