Metabolism II

Question 1

What is glucose stored as?

Answer 1

Glycogen or starch

Question 2

What is the formula for glucose oxidation?

Answer 2

C6H12O6+6O2–>6CO2+6H2O+heat+light

Question 3

What is cellular respiration?

Answer 3

REDOX reactions that produce the free energy that is used to synthesize ATP
Divided into glycolysis, pyruvate oxidation, citric acid cycle, and the electron transport chain

Question 4

What are the two fundamental requirements of cells?

Answer 4

• Energy to generate ATP

- source of C to use as a raw building material for macromolecule synthesis

Question 5

What is glycolysis?

Answer 5

The transformation of glucose into two pyruvate molecules

Question 6

What is the net gain of glycolysis?

Answer 6

ATP: +2
NADH: +2 NADH
H2O: +2 H2O

Question 7

What are the steps of glycolysis? Include enzyme names for each step

Answer 7

1) glucose–>glucose-6-phosphate (hexokinase)
2) glucose 6-phospahte–>fructose 6-phosphate (phosphoglucose isomerase)
3) fructose 6-phoshate–>fructose 1,6-bisphosphate (phosphofructokinase)
4) fructose 1,6-bisphosphate–>glyceraldehyde 3-phosphate+dihydroxyacetone phosphate (fructose-bisphosphate aldolase)
5) G3P+DHAP–>(2)G3P (triose phosphate isomerase)
6) (2)G3P–>(2)1,3-bisphosphate (G3P dehydrogenase)
7) (2)1,3-bisphosphate–>(2)3-phosphoglycerate (phosphoglycerate kinase)
8) (2)3-phosphoglycerate–>(2)2-phosphoglycerate (phosphoglycerate mutase)
9) (2)2-phosphoglycerate–>(2)phosphoenol pyruvate (enolase)
10) (2)PEP–>(2)pyruvate (pyruvate kinase)

Question 8

What are the steps of the preparatory phase of glycolysis?

Answer 8

Steps 1 through 4

Question 9

What are the steps of the payoff phase of glycolysis?

Answer 9

Steps 5 through 10

Question 10

Feedback inhibition occurs when …

Answer 10

a product of a metabolic pathway inhibits an enzyme that functions early in the pathway

Question 11

When and how does feedback inhibition occur in glycolysis?

Answer 11

High levels of ATP inhibit phosphofructokinase (in Step 3)
It has two binding sites for ATP: when it binds to the active site it catalyzes Step 3 but when levels are high t binds to a regulatory site which inhibits Step 3

Question 12

What is substrate-level phosphorylation and in which step(s) of cellular respiration does it occur?

Answer 12

When ATP is produced by the enzyme-catalyzed transfer of P from an intermediate to ADP
It happens in glycolysis and the citric acid cycle

Question 13

What is oxidative phosphorylation and in which step(s) of cellular respiration does it occur?

Answer 13

When a proton gradient provides the energy for ATP synthesis, ATP synthase (a membrane protein) uses energy to phosphorylate ADP+P–>ATP
It happens in the ETC

Question 14

What is the equation for pyruvate oxidation?

Answer 14

pyruvate+CoA-SH+NAD+–>acetyl-CoA+NADH+H+

Question 15

What is the net gain of pyruvate oxidation?

Answer 15

NADH: +1NADH/pyruvate so +2NADH/glucose molecule

Question 16

What is the feedback inhibition associated with pyruvate oxidation?

Answer 16

When products of glycolysis and pyruvate oxidation are abundant they phosphorylate pyruvate dehydrogenase which changes its shape and inhibits it

Question 17

What is the name of the enzyme complex where pyruvate oxidation takes place?

Answer 17

Pyruvate dehydrogenase

Question 18

What are the steps of the citric acid cycle?

Answer 18

1) oxaloacetate+acetyl-CoA–>citrate
2) citrate–>cis-aconitate–>isocitrate
3) isocitrate–>α-ketoglutarate
4) α-ketoglutarate–>succinyl-CoA
5) succinyl-CoA–>succinate
6) succinate–>fumarate
7) fumarate–>malate
8) malate–>oxaloacetate
The cycle happens twice/glucose molecule

Question 19

What is the net gain of the citric acid cycle?

Answer 19

ATP: +1ATP/cycle so +2ATP/glucose (from GTP)
NADH: +3NADH/cycle so +6NADH/glucose
FADH2: +1FADH2/cycle so +2FADH2/glucose
CO2: +2CO2/cycle so +4CO2/glucose

Question 20

What are anaplerotic reactions?

Answer 20

Reactions that replenish depleted intermediates of a metabolic pathway

Question 21

What is glucose oxidation?

Answer 21

The combination of glycolysis, pyruvate oxidation, and the citric acid cycle

Question 22

What are the net gains of glucose oxidation?

Answer 22

ATP: +4ATP
NADH: +10NADH
FADH2: +2FADH2
CO2: +6CO2

Question 23

What does amphibolic mean?

Answer 23

Biological pathways that involve both anabolic and catabolic reactions
Ex. the citric acid cycle