Question 1

You have isolated some muscle cells in a tissue culture system.You are able to get them to contract in culture.If you add an inhibitor of the electron transport system to these cells,they do not contract quite as much,but they still contract noticeably.What kind of muscle fiber type are you employing?

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Question 2

If fatty acids are a more efficient storehouse of energy than glucose or glycogen,why aren't they used immediately to drive muscle contraction?

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Question 3

In addition to driving the synthesis of ATP,what other processes in the mitochondria are driven by the proton-motive force?

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Question 4

There are four large complexes of electron transport molecules in the inner mitochondrial membrane.There are also two smaller proteins that carry electrons between the complexes.What is a possible reason for the much smaller size of these shuttle proteins,cytochrome c and ubiquinone?

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Question 5

A preparation of submitochondrial particles is made.The particles are able to oxidize substrates,generate a proton gradient and make ATP.If the particles are treated with urea,what happens? If DNP is added,what happens? How does DNP make the inner mitochondrial membrane permeable to protons?

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Question 6

You prepare red blood cell ghosts with a very high internal potassium ion concentration and a very high external sodium ion concentration,higher than normally exists in the body.The red blood cell ghost also contains ADP and inorganic phosphate ions in the interior and the Na⁺-K⁺ pump in the membrane.What happens?

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Question 7

Why are molecules that block oxidative phosphorylation and the electron transfer chain such dangerous and potentially deadly poisons?

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Question 8

You are a world-wide expert in mitochondria.If an investigator tells you that he wishes to study mitochondrial uncoupling proteins,what kind of organism would you suggest he use as a source of the protein? What is the function of brown adipose tissue? Humans lose brown fat deposits as they age.How does that happen and how do humans maintain body temperature when the brown fat is gone? Uncoupling protein (UCP)isoforms are found in cells of the nervous system.While their roles are debated,what is the most prominent hypothesis that may explain their function?

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Question 9

How many carbons from an original glucose molecule get into the TCA cycle? What happens to the carbons that do not enter the cycle?

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Question 10

You treat some cells with DNP and discover that ATP production ceases.Upon closer examination,you also note that the number of calcium ions sequestered in the mitochondrion decreases.Please explain.

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Question 11

A doctor in a hospital emergency room sees an obese patient who has come into the emergency room.He has been losing weight rapidly but complains that he has lost energy and is tired most of the time.During his interview with the patient,the doctor thinks he has discovered what is causing the man's condition.What do you think he has found?

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Question 12

What properties do mitochondria and peroxisomes have in common?

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Question 13

You are studying the enzyme kinetics of enzymes in the TCA cycle.You add a molecule to the mixture that appears to act as a competitive inhibitor of one of the enzymes.At first,you cannot tell which enzyme is inhibited,but you can tell that it is bound to the inner mitochondrial membrane.Can you guess which TCA enzyme you have inhibited and how do you know?

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Question 14

Which person would tend to have a higher proportion of slow-twitch than fast-twitch muscles: a weight lifter,a sprinter,or a long distance runner?

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Question 15

Given the overall equation for respiration: C₆H₁₂O₆ + 6O₂ <-> 6CO₂ + 6H₂O,at what point in respiration are the reactants used up and the products made?

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Question 16

Where did peroxisomes get their name? How is the toxic hydrogen peroxide generated by these organelles disposed of? What is the specialized type of peroxisome found in plant seedlings and what specialized function do these organelles perform?

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Question 17

Rat liver mitochondria are isolated and placed in an assay medium.What happens to the pH of the medium when the medium is kept anaerobic? What happens when O₂-saturated saline is added to the mixture?

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Question 18

Which reaction releases more free energy - the removal of a phosphate group from creatine phosphate or the removal of a phosphate group from ATP?

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Question 19

Observations of two different cell types indicate a couple of differences in their mitochondria.Cell type 1 has 2-3 times the mitochondria of Cell Type 2.The mitochondria in Cell Type 1 are also larger,contain more cristae and the cristae extend farther across the mitochondria than in Cell Type 2.Which cell type is likely to have more extensive energy requirements?

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Question 20

What are some of the diverse activities in which the enzymes found in peroxisomes are involved?

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Quiz 5: Aerobic Respiration and the Mitochondrion