Reasons for Inexact ATP Generation in Cellular Respiration

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Questions and Answers

What is the yield of ATP per NADH in liver cells and heart cells?

2.5 ATP (correct)

3.5 ATP

1.5 ATP

4.5 ATP

What is the maximum number of ATP produced by oxidative phosphorylation per glucose molecule?

28 ATP (correct)

25 ATP

30 ATP

32 ATP

What is the energy released per mole of glucose under standard conditions?

686 kcal/mol (correct)

886 kcal/mol

786 kcal/mol

586 kcal/mol

What is the approximate efficiency of cellular respiration?

34% Signup and view all the answers

What is the function of the proton-motive force in the mitochondria?

To drive other kinds of work Signup and view all the answers

What is the purpose of the uncoupling protein in brown fat?

To generate heat Signup and view all the answers

What is the result of the buildup of ATP in cells?

Decreased cellular respiration Signup and view all the answers

What is the purpose of the adaptation in hibernating mammals?

To generate heat Signup and view all the answers

What is the approximate percentage of chemical energy in glucose that is lost as heat?

66% Signup and view all the answers

What is the advantage of the adaptation in hibernating mammals?

It allows for maintenance of internal body temperature Signup and view all the answers

Why can't we state an exact number of ATP molecules generated by the breakdown of one molecule of glucose?

Because phosphorylation and the redox reactions are not directly coupled to each other. Signup and view all the answers

What is the approximate number of H+ that must reenter the mitochondrial matrix via ATP synthase to generate 1 ATP?

4 H+ Signup and view all the answers

How many ATP molecules can be generated by a single molecule of NADH?

2.5 ATP Signup and view all the answers

How many ATP molecules can be generated by a single molecule of FADH2?

1.5 ATP Signup and view all the answers

Why does the ATP yield vary slightly depending on the type of shuttle used?

Because the shuttle affects the proton-motive force generated. Signup and view all the answers

What is the purpose of electron shuttle systems?

To transport electrons from the cytosol into the mitochondrion. Signup and view all the answers

What happens to the electrons of NADH captured in glycolysis?

They are conveyed into the mitochondrion by electron shuttle systems. Signup and view all the answers

How many ATP molecules can result from each NADH that was originally generated in the cytosol in brain cells?

1.5 ATP Signup and view all the answers

Study Notes

Reasons for Inexact ATP Yield

Three reasons for inexact ATP yield: phosphorylation and redox reactions not directly coupled, ATP yield varies depending on electron shuttle used, and proton-motive force used for other work
Ratio of NADH to ATP molecules not a whole number

ATP Yield from NADH

1 NADH generates enough proton-motive force for 2.5 ATP synthesis
Each FADH2 generates enough proton-motive force for 1.5 ATP synthesis
ATP synthesis takes into account energetic cost of moving ATP from mitochondrion to cytosol

Electron Shuttle Systems

Mitochondrial inner membrane impermeable to NADH
Electrons from NADH in cytosol conveyed into mitochondrion by electron shuttle systems
Electrons passed to FAD or NAD+ in mitochondrial matrix
ATP yield varies depending on electron shuttle used (1.5 ATP or 2.5 ATP per NADH)

Proton-Motive Force and ATP Yield

Proton-motive force used for other work, reducing ATP yield
Maximum ATP yield from oxidative phosphorylation is 28 ATP, plus 4 ATP from substrate-level phosphorylation (total 32 ATP or 30 ATP with less efficient shuttle)

Efficiency of Respiration

Efficiency of respiration is percentage of chemical energy in glucose transferred to ATP
7.3 kcal per mole of ATP stored, with 686 kcal of energy released per mole of glucose
Efficiency of respiration is approximately 34%

Cellular Respiration and Energy Conversion

Cellular respiration remarkably efficient in energy conversion
Comparison to automobile efficiency (25%)
Remaining energy lost as heat, used to maintain body temperature and dissipated through sweating and cooling mechanisms

Hibernation and Reduced Metabolic Efficiency

Hibernating mammals reduce metabolic efficiency to generate heat without ATP production
Brown fat tissue contains mitochondria with uncoupling protein, allowing protons to flow back down concentration gradient without generating ATP
Adaptation allows for heat generation without buildup of ATP, which would shut down cellular respiration

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Description

This quiz explores the reasons why the number of ATP molecules generated by glucose breakdown is inexact, including the decoupling of phosphorylation and redox reactions.