Chapter 7

Question 1

What is cellular respiration?

Answer 1

A process by which living cells obtain energy from organic molecules and release waste products.

Question 2

How is metabolism different than other chemical reactions?

Answer 2

Metabolism that occurs in living cells is extremely controlled.

Question 3

What is aerobic respiration?

Answer 3

A type of cellular respiration in which O2 is consumed and CO2 is released.

Question 4

What are the three energy intermediates that are released in addition to heat when certain chemical bonds in glucose are broken?

Answer 4

ATP, NADH, FADH2

Question 5

What are the four metabolic pathways of anaerobic cellular respiration that lead to the release of ATP, NADH, and FADH2?

Answer 5

1. Glycolysis
2. the breakdown of pyruvate
3. citric acid cycle
4. oxidative phosphorylation

Question 6

Describe Glycolysis:

Answer 6

A metabolic pathway that breaks down glucose into 2 pyruvate molecules (3 carbons each), producing a net energy yield of 2 ATP and 2 NADH molecules. ATP is synthesized through substrate-level phosphorylation.

Question 7

Where does Glycolysis take place?

Answer 7

In the cytosol

Question 8

Describe the breakdown of pyruvate:

Answer 8

The two pyruvate molecules are further broken down into an acetyl group (2 carbons each) and one CO2 molecule. One NADH is made for every pyruvate molecule that is oxidized.

Question 9

Describe the citric acid cycle (formally know as the Krebs cycle):

Answer 9

Each acetyl group is incorporated into an organic molecule and is later oxidized to release 2 CO2. This process results in the creation of 1 ATP, 3 NADH, and 1 FADH2. So, a total of 2 ATP, 6 NADH, 2 FADH2, and 4 CO2.

Question 10

Where does the breakdown of pyruvate and the citric acid cycle occur?

Answer 10

In the mitochondrial matrix.

Question 11

Describe oxidative phosphorylation:

Answer 11

High-energy electrons taken from NADH and FADH2 are transported via the H+ electrochemical gradient to make more ATP via the phosphorylation of ADP and Pi.

Question 12

What does chemiosmosis refer to?

Answer 12

A process for making ATP in which energy stored in an ion electrochemical gradient is used to make ATP from ADP and Pi.

Question 13

How many ATPs are made via oxidative phosphorylation?

Answer 13

Approximately 30-34 ATP molecules.

Question 14

Where does oxidative phosphorylation occur?

Answer 14

In eukaryotes, it occurs along the cristae. In bacteria and archaea it occurs along the plasma membrane.

Question 15

What are the three phases of Glycolysis?

Answer 15

1. (steps 1-3) Energy investment phase
2. (steps 4-5) Cleavage phase
3. (steps 6-10) Energy liberation phase

Question 16

Why don’t we make too much ATP?

Answer 16

When a cell has a sufficient amount of ATP, feedback inhibition occurs. At high concentrations, ATP binds to an allosteric site on the phosphofructokinase enzyme and causes a confrontational change that render the enzyme useless.

Question 17

What is Coenzyme A?

Answer 17

An organic molecule that attaches to acetyl via a covalent bond. The hydrolysis of this bond releases a large amount of free energy, making it possible for the acetyl group to attach to be transferred to other organic molecules.

Question 18

Define metabolic cycle:

Answer 18

A biochemical cycle in which particular molecules enter while others leave; the process is cyclical because it involves a series of organic molecules that are regenerated with each turn of the cycle.

Question 19

How is the citric acid cycle controlled?

Answer 19

The rate of the cycle is largely regulated by the availability of substrates acetyl-CoA and NAD+ and by feedback inhibition.

Question 20

What is the electron transport chain (ETC) (also called the respiratory chain)?

Answer 20

A group of protein complexes and small organic molecules within the inner membranes of mitochondria and chloroplasts and the plasma membrane of prokaryotes. The components accept and donate electrons to each other in a linear manner and produce a H+ electrochemical gradient.

Question 21

What molecule is at the end of the respiratory chain?

Answer 21

Oxygen, which is the most electronegative.

Question 22

How is oxidative phosphorylation controlled?

Answer 22

This process is regulated by a variety of factors, including the availability of ETC substrates, such as NADH and O2, and by the ATP/ADP ratio.

Question 23

What are the two main reasons we don’t make the maximum amount of ATP during oxidative phosphorylation?

Answer 23

1. NADH and FADH2 are also used for anabolic pathways.

2. Some of the energy in the H+ gradient is used for other purposes.

Question 24

What does anaerobic mean?

Answer 24

Refers to an environment that lacks oxygen or a process that occurs in the absence of oxygen; a form of metabolism that does not require oxygen.

Question 25

What are the two different ways cells can metabolize organic molecules in the absence of oxygen?

Answer 25

1. Anaerobic respiration

2. Fermentation

Question 26

What is anaerobic respiration?

Answer 26

The breakdown of organic molecules in the absence of oxygen by using a final electron acceptor that is something other than oxygen.

Question 27

What is fermentation?

Answer 27

The breakdown of organic molecules to produce energy without any net oxidation of an organic molecule.

Question 28

Why are prolonged anaerobic conditions problematic for glycolysis?

Answer 28

1st Because fermentation requires a fresh supply of NAD+
2nd Because high concentrations of NADH mean less efficient donation of electrons and the promotion of the formation of dangerous free radicals.

Question 29

What is the product of fermentation in muscle cells?

Answer 29

Lactate, which increases NAD+ and can later be converted back to pyruvate.

Question 30

What is produced by the fermentation of yeast cells?

Answer 30

Ethanol

Question 31

What is the ATP yield of glycolysis in anaerobic conditions?

Answer 31

2 ATP molecules

Question 32

What is the final protein in the electron transport train?

Answer 32

cytochrome oxidase