AP Biology Unit 3 Krebs Cycle

Where does the Krebs cycle take place?

• Mitochondrial matrix

• Mitochondrial cristae

• Cytosol

• Chloroplast

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What is the starting material for the Krebs cycle?

• Glucose

• Pyruvate

• Acetyl CoA

• G3P

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How much of the glucose is left after the Krebs cycle?

• 0%

• 25%

• 50%

• 75%

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The Krebs cycle requires oxygen because...

• Without oxygen, NADH cannot be oxidized to continue receiving electrons as NAD+

• Without oxygen coenzyme A is unable to be added to the pyruvate molecule to make acetyl CoA

• Without oxygen ATP cannot be synthesized by substrate level phosphorylation

• Without oxygen glycolysis cannot take place to provide the starting materials for the Krebs cycle

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What is the difference between NADH and FADH₂?

• Both are electron carriers, FADH₂ occurs in the Krebs cycle and NADH occurs in glycolysis

• Both are electron carriers, NADH occurs in the Krebs cycle and FADH₂ occurs in glycolysis

• Both are electron carriers, FADH₂ holds higher energy electrons

• Both are electron carriers, NADH holds higher energy electrons

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How are electrons extracted during the Krebs cycle transferred to the electron transport chain?

• NADH

• FADH₂

• ATP

• CO₂

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In one turn of the cycle, how many of the products are formed?

• 1 ATP, 2 NADH, 2 FADH₂, 1 CO₂

• 1 ATP, 3 NADH, 1 FADH₂, 2 CO₂

• 2 ATP, 2 NADH, 1 FADH₂, 1 CO₂

• 2 ATP, 3 NADH, 2 FADH₂, 2 CO₂

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How does the Krebs cycle allow for ATP synthesis?

• The rotation of the Krebs cycle turns a "rotor" in the cell to synthesize ATP

• ATP is synthesized by substrate level phosphorylation during the removal of the coenzyme A upon entrance into the cycle

• Krebs cycle completes the breakdown of glucose to release the energy and store it in the form of ATP

• High energy electrons are stored in NADH and FADH₂ to shuttle to the ETC to generate a proton gradient

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How many turns of the Krebs cycle per glucose molecule?

• 1

• 2

• 3

• 4

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Predict the effect of an inhibitor that stops the oxidation of NADH or FADH₂.

• Increase of cellular respiration; more ATP is synthesized

• Decrease of cellular respiration; more ATP is synthesized

• Increase of cellular respiration; less ATP is synthesized

• Decrease of cellular respiration; less ATP is synthesized

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