Question 1

If three molecules of glucose went through glycolysis and into the citric acid cycle, how many times would the preparatory reaction occur?

Accepted Answer

Each molecule of glucose is broken down into two molecules of pyruvate. Each molecule of pyruvate enters the mitochondria, therefore, the preparatory reaction needs to occur twice per molecule of glucose, since we started with 3 glucose multiplied by two equals six.

Question 2

Which of the following is not a product of cellular respiration?

Accepted Answer

Oxygen is a reactant in cellular respiration, not a product.

Question 3

When you exhale what two stages of cellular respiration produce the carbon dioxide you are breathing out?

Accepted Answer

Carbons are pulled off of the carbon skeleton and released out of our bodies as carbon dioxide. The carbons are oxidized in the preparatory reaction step and in the citric acid cycle.

Question 4

What happened to the hamburger you had for lunch?

Accepted Answer

All of the molecules consumed can be utilized either to make ATP or to make the molecules necessary for the cell to function; their fate depends on the needs of the cell.

Question 5

As electrons are passed down the electron transport chain, the energy released is used immediately to ________.

Accepted Answer

The energy released by oxidation-reduction is used to pump H⁺from the mitochondrial matrix into the intermembrane space located between the outer and inner membrane of a mitochondrion. The pumping of H⁺ into the intermembrane space establishes an unequal distribution of H⁺; in other words, there are many H⁺ in the intermembrane space and few in the matrix of a mitochondrion.

Question 6

A product of glycolysis is ______

Accepted Answer

During glycolysis a six carbon glucose molecule is broken down into two, three carbon molecules of pyruvate.

Question 7

As a result of glycolysis there is a NET gain of _______ ATPs.

Accepted Answer

2 ATPs are used to start glycolysis, 4 ATPs are produced by substrate level ATP synthesis. Therefore, there is a net gain of 2 ATP.

Question 8

Where in the cell does glycolysis occur?

Accepted Answer

Glycolysis occurs in the cytoplasm outside the mitochondria.

Question 9

The energy of the electrons passing along the electron transport chain is used to produce ____.

Accepted Answer

As oxidation-reduction occurs down the electron transport chain, energy is released that will be used to make ATP.

Question 10

The product of the preparatory reaction is ________.

Accepted Answer

Pyruvate from glycolysis is oxidized to a 2 carbon molecule that is carried by coenzyme A (CoA) to the citric acid cycle.

Question 11

During hibernation the rate of cellular respiration in a mammal is typically less than half the rate measured when the mammal is not hibernating. This slowed cellular respiration is probably accompanied by which of the following.

Accepted Answer

The extra energy from cellular respiration is lost in the form of heat. The decrease in cellular respiration and energy use would result in a decrease in the animal's heart rate.

Question 12

The cristae of a mitochondrion are critical ________.

Accepted Answer

The cristae of mitochondria contain an ATP synthase complex that allows H1 to return to the matrix. The flow of H1 through the ATP synthase complex brings about a conformational change, which causes the enzyme ATP synthase to synthesize ATP from ADP+ P. ATP leaves the matrix by way of a channel protein.

Question 13

Cellular respiration can be described as the conversion of the energy ________.

Accepted Answer

Food contains energy trapped in bonds within molecules. Cellular respiration releases that energy and captures it again storing it within ATP molecules. ATP are energy rich molecules that run cellular activities.

Question 14

The final electron acceptor at the end of the electron transport chain is ___ resulting in formation of ___.

Accepted Answer

Oxygen is the final electron acceptor in the electron transport chain. Once oxygen accepts electrons, it combines with H⁺ to form a water molecule, as a by-product.

Question 15

The products of fermentation depend on the type of organism carrying out the process. Yeasts are used to produce

Accepted Answer

Yeast carries out alcohol fermentation. The alcohol is used in the production of beer and wine, and the CO₂ given off is used in the production of bread.

Question 16

Susan suffered from a heart attack. When the doctors tested the heart muscle they found that she had an increased ratio of lactic acid to pyruvic acid in her heart. What does this say about the availability of oxygen in her heart muscle cells?

Accepted Answer

Lactic acid is an indication that lactic acid fermentation is occurring in muscle cells. Lactic acid fermentation occurs only in the absence of oxygen; thus, the heart cells may not have been receiving enough oxygen, a factor that could contribute to the occurrence of a heart attack. The level of lactic acid could be measured in certain parts of the heart as an indication of risk of heart attack.

Question 17

Glycolysis and the citric acid cycle are similar in that they both produce ________.

Accepted Answer

NAD+ accepts hydrogen atom and becomes NADH in both reactions. NADH will be used in the last step of cellular respiration, the e-transport chain. ATP is also produced in both reactions.

Question 18

Your friend has been on a diet and loses 15 pounds of fat. After studying cellular respiration how can you explain the weight loss, where did the weight go (how was it lost)?

Accepted Answer

Fats are oxidized to release energy. Hydrogen atoms are removed from glucose and to oxygen atoms. The by-products are carbon dioxide and water.

Question 19

What must pyruvic acid be converted into before it can enter the citric acid cycle?

Accepted Answer

Pyruvate is oxidized, and a CO₂ is given off. A C₂ acetyl group is attached to coenzyme A forming acetyl-CoA

Question 20

The citric acid cycle starts with ________ and yields ___________.

Accepted Answer

The citric acid cycle starts with the products from the preparatory step that meet up with C₄ molecules already present in the mitochondrial matrix. Two carbons are pulled off and released as carbon dioxide, leaving a C₄ molecule allowing the process to occur again. Both NAD+ and FAD accept hydrogen atoms, resulting in NADH and FADH₂.

Quiz 7: Energy for Cells