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3.5 Cellular Respiration: revision map

The subtopic in the middle and five tasks round it: label a diagram, complete a table, put a process in order and fill 12 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.

Unit 3 practice questionsThe whole Unit 3 map

Topic 3.5

Cellular Respiration

AP Biology · Unit 3 Cellular EnergeticsName

3.5.A, 3.5.BRespiration in the cell

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  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6

3.5.AWhere the carbon goes

The carbon atoms of glucose are released as , mostly in pyruvate oxidation and the Krebs cycle, and the hydrogen ends up in water. Most ATP comes from the proton gradient rather than directly from the cycle itself, which is why a poison that blocks the electron transport chain stops nearly all ATP production.

3.5.AThe stages

StageWhereInputsMain outputs
cytosolglucose2 pyruvate, 2 ATP (net), 2 NADH
Pyruvate oxidationmitochondrial matrixpyruvateacetyl CoA, CO₂, NADH
mitochondrial matrixacetyl CoACO₂, ATP, NADH, FADH₂
Oxidative phosphorylationinner mitochondrial membraneNADH, FADH₂, O₂, water
Topic 3.5Cellular Respiration

3.5.BChemiosmosis

Number the steps in order.

  1. Electrons pass from carrier to carrier, releasing energy.
  2. Oxygen accepts the electrons at the end and forms water.
  3. Protons flow back through ATP synthase and ATP is made.
  4. NADH and FADH₂ give up electrons to the electron transport chain.
  5. The energy is used to pump protons across the inner membrane.

3.5.BWithout oxygen

If oxygen is missing, the electron transport chain stops and NADH cannot be oxidized. Cells carry on with glycolysis, and regenerate NAD⁺ by . Animal cells reduce pyruvate to lactate, and yeast convert it to ethanol and CO₂. This gives only ATP per glucose, compared with about 30 to 32 from aerobic respiration, but it works quickly.

Word bank 2ATPATP synthasecarbon dioxideelectron transport chainfermentationglycolysisGlycolysisKrebs cycleoxygenpyruvate

Answer key

Every box on the sheet with its gaps filled in, as the subtopic reads in full.

  1. LabelRespiration in the cell

    1. glycolysis
    2. pyruvate
    3. Krebs cycle
    4. electron transport chain
    5. ATP synthase
    6. oxygen

  2. TableThe stages

    StageWhereInputsMain outputs
    Glycolysiscytosolglucose2 pyruvate, 2 ATP (net), 2 NADH
    Pyruvate oxidationmitochondrial matrixpyruvateacetyl CoA, CO₂, NADH
    Krebs cyclemitochondrial matrixacetyl CoACO₂, ATP, NADH, FADH₂
    Oxidative phosphorylationinner mitochondrial membraneNADH, FADH₂, O₂ATP, water

  3. OrderChemiosmosis

    1. NADH and FADH₂ give up electrons to the electron transport chain.
    2. Electrons pass from carrier to carrier, releasing energy.
    3. The energy is used to pump protons across the inner membrane.
    4. Protons flow back through ATP synthase and ATP is made.
    5. Oxygen accepts the electrons at the end and forms water.

  4. GapsWithout oxygen

    If oxygen is missing, the electron transport chain stops and NADH cannot be oxidized. Cells carry on with glycolysis, and regenerate NAD⁺ by fermentation. Animal cells reduce pyruvate to lactate, and yeast convert it to ethanol and CO₂. This gives only 2 ATP per glucose, compared with about 30 to 32 from aerobic respiration, but it works quickly.

  5. GapsWhere the carbon goes

    The carbon atoms of glucose are released as carbon dioxide, mostly in pyruvate oxidation and the Krebs cycle, and the hydrogen ends up in water. Most ATP comes from the proton gradient rather than directly from the cycle itself, which is why a poison that blocks the electron transport chain stops nearly all ATP production.