Respiration - PP Exam 2

Question 1

What are the four steps of aerobic respiration? (Slide9Lecture12)

Answer 1

glycolysis, oxidation of pyruvate to acetylCoA, citric acid cycle (Krebs cycle), and electron transport chain

Question 2

What is the main form of carbon obtained by plant cells through the phloem?

Answer 2

sucrose

Question 3

What two enzymes can break down sucrose into hexoses?

Answer 3

invertase and sucrose synthase

Question 4

What does the conversion of sucrose to hexose phosphate regulate?

Answer 4

-carbohydrate metabolism
-allocation of fixed carbon dioxide to glycolysis and the pentose phosphate pathway

Question 5

For glycolysis rxns that break hexose-P into triose-P, where can they occur?

Answer 5

both the cytoplasm and the plastids

Question 6

Where does glycolysis occur?

Answer 6

cytosol

Question 7

Where does the oxidation of pyruvate to acetyl-CoA occur?

Answer 7

mitochondria

Question 8

Where does the Krebs Cycle occur?

Answer 8

mitochondria

Question 9

Where does the ETC of respiration occur?

Answer 9

the inner mitochondrial membrane

Question 10

Why is the Krebs cycle also called the “Citric Acid Cycle”?

Answer 10

because citric acid is the first intermediate formed in the cycle

Question 11

Why is the Krebs Cycle also called the “Tricarboxylic Acid Cycle”?

Answer 11

because some intermediates produced are tricarboxylic acids

Question 12

Explain how glycolysis occurs.

Answer 12

Glycolysis is the process where sucrose gets converted to pyruvate. It occurs in the following steps:

• sucrose is converted to hexoses by invertase or sucrose synthase
  -hexoses converted to fructose-6-phosphate
  -fructose-1-phosphate converted to fructose-1,6-bisphosphate by phosphofructokinase
  -fructose-1,6-bisphosphate converted to triose-P
  -triose-P converted to phosphoenolpyruvate
  -phosphoenolpyruvate converted to pyruvate

Question 13

What are the main products of glycolysis?

Answer 13

4 pyruvate molecules, 4 ATP molecules, 4 NADH molecules

Question 14

What inhibits phosphofructokinase? How does it inhibit?

Answer 14

phosphoenolpyruvate

phosphoenolpyruvate is produced by triose-P later in glycolysis, so when the cell senses phosphoenolpyruvate it doesn’t want to waste ATP on making more triose-P’s, as it thinks it already did

Question 15

What activates phosphofructokinase?
How does it activate?

Answer 15

high concentration of phosphate

because phosphates are at high concentration when ATP is being hydrolyzed (used), so the cell wants to complete glycolysis which produces more ATP

Question 16

Explain how the oxidation of pyruvate to acetyl-CoA occurs.

Answer 16

-pyruvate is converted to acetly-CoA by pyruvate dehydrogenase

Question 17

Explain how the Krebs Cycle occurs.

Answer 17

-acetyl-CoA is converted to CO2 by a series of reactions

-produces oxaloacetate, which is regenerated in the cycle and used again

-produces 2 CO2’s, 1 ATP, 3 NADH, and 1 FADH2 (all per 1 acetyl-CoA)

-the intermediates formed during the Krebs Cycle (specific names not important) used to synthesize other organic compounds

Question 18

Explain the ETC of mitochondrial NADH to O2.

Answer 18

The electron (H+) flows in the following series:

NADH
complex I
ubiquinone
complex III
cytochrome c
complex IV

Question 19

Explain the ETC of FADH2 to O2.

Answer 19

The electron flows in the following series:

FADH2
complex II (aka ‘succinate dehydrogenase’)
ubiquinone
complex III
cytochrome c
complex IV

Question 20

How does the ETC of respiration fuel the synthesis of ATP?

Answer 20

The ETC forms a H+ gradient, which is used as an energy source for ATP synthase to synthesize ATP

Question 21

Explain the ETC of cytoplasmic NADH to O2.

Question 22

Explain the ETC of mitochondrial NADH.

Answer 22

NADH to ubiquinone to alternative oxidase to end products

Question 23

What is the Pentose Phosphate Pathway?

Question 24

What does pyruvate kinase do?

Answer 24

it converts phosphoenolpyruvate to pyruvate

Question 25

How many ATPs are formed in glycolysis per sucrose?

Answer 25

4

Question 26

How many pyruvate molecules are formed in glycolysis per sucrose?

Answer 26

4

Question 27

How many NADHs are formed in glycolysis per sucrose?

Answer 27

4

Question 28

What does pyruvate dehydrogenase do?

Answer 28

It converts pyruvate to acetyl-CoA

Question 29

What inhibits pyruvate dehydrogenase? Why?

Answer 29

NADH

its a product, so inhibits

Question 30

What activates pyruvate dehydrogenase? Why?

Answer 30

pyruvate

its a substrate, so activates