review slides

Question 1

glycolysis is a ______ process

Answer 1

amphibolic

Question 2

what are the two stages of glycolysis?

Answer 2

1. traps glucose in the cell and modifies it so that it can be cleaved into a pair of phosphorylated 3- carbon compounds
2. oxidizes the 3- carbon compounds to pyruvate while generating 2 molecules of ATP

Question 3

phosphofructokinase is the key regulator of glycolysis in mammals. the enzyme is allosterically _______ and allosterically _______

Answer 3

it is allosterically inhibited by ATP

and allosterically simulated by AMP

Question 4

glycolysis converts one molecule of glucose to ___ molecules of pyruvate with the generation of _____ molecules of ATP

Answer 4

2 pyruvate

2 ATP

Question 5

when ATP needs are great, _____ generates ATP from 2 ADP. AMP then becomes the signal for low energy state

Answer 5

adenylate kinase

Question 6

hexokinase is allosterically ____________-

Answer 6

inhibited by glucose 6-phosphate

Question 7

pyruvate kinase is inhibited by _____ and _____, but stimulated by __________

Answer 7

inhibited: allosteric signals of ATP and alanine

stimulated:
fructose 1,6 bisphosphate

Question 8

in muscle, glycolysis is regulated to meet the energy needs of _______–

Answer 8

contraction

Question 9

Pyruvate kinase is regulated by allosteric effectors and ________________.
Pyruvate kinase in the liver is regulated allosterically as it is in muscle. However, liver pyruvate kinase is also regulated by covalent modification. Low blood glucose leads to the phosphorylation and inhibition of liver pyruvate kinase.

Answer 9

Covalent modification

Question 10

Which activity of the bifunctional enzyme is determined by blood glucose levels?

Answer 10

A low blood-glucose level as signaled by glucagon leads to the phosphorylation of the bifunctional enzyme and, hence, to a lower level of fructose 2,6-bisphosphate, slowing glycolysis. High levels of fructose 6-phosphate accelerate the formation of fructose 2,6-bisphosphate by facilitating the dephosphorylation of the bifunctional enzyme.

Question 11

Which activity of the bifunctional enzyme is determined by blood glucose levels?

Answer 11

A low blood-glucose level as signaled by glucagon leads to the phosphorylation of the bifunctional enzyme and, hence, to a lower level of fructose 2,6-bisphosphate, slowing glycolysis. High levels of fructose 6-phosphate accelerate the formation of fructose 2,6-bisphosphate by facilitating the dephosphorylation of the bifunctional enzyme.

Question 12

To generate reducing equivalents, NADPH, for reductive _______reactions.

2. To provide the cell with ribose-5-phosphate (R5P) for the ________ of the nucleotides and nucleic acids.
3. Minor: Metabolize dietary pentose sugars derived from the digestion of nucleic acids as well as to rearrange the carbon skeletons of dietary carbohydrates into glycolytic/gluconeogenic intermediates.

Answer 12

Biosynthesis reactions

synthesis

Question 13

what enyzme regulate the citiric acid cycle?

Answer 13

pyruvate dehydrogenase

isocitrate dehydrogenase

alpha ketogluturate dehydrogenase

Question 14

glycolysis (activated by ?)

PFK1=
pyruvate kinase=
insulin=

Answer 14

PFK-1 activated by:
AMP
Fructose-2,6-bisphosphate

Pyruvate kinase
AMP
Fructose-2,6-bisphosphate (feed forward)

Insulin stimulates synthesis of:
Gluokinase
PFK-1
PFK-2

Question 15

(activated by?)

pyruvate carboxylase=

frutose 1,6 bisphosphate

glucagon stimulates sythesis of:

Answer 15

Pyruvate carboxylase is activated by:
Acetyl-CoA (high during starvation; product of fatty acid catabolism)

Fructose 1,6-bisphosphatase activated by:
ATP

Glucagon stimulates synthesis of:
PEP carboxykinase
Fructose-1,6-bisphosphatase
Glucose-6-phosphatase

Question 16

Gluconeogeneis inhibited by?

pyruvate carboxlase

frutose 1-6 bisphosphatase

Answer 16

Gluconeogenesis
Pyruvate carboxylase inhibited by:
Acetyl CoA
Fructose-1,6-

bisphosphatase inhibited by:
AMP
Fructose-2,6-bisphosphate (indicates high level of glucose)

Question 17

glycosylsis inhibited by?

hexokinase=?
PFK1?
pyruvate kinase?

Answer 17

Glycosylsis

Hexokinase is inhibited by:
ATP
Glucose-6-phosphate

PFK-1 inhibited by:
ATP
Citrate

Pyruvate kinase inhibited by:
ATP
Acetyl CoA

Question 18

goal of pentose phosphate pathway?

Answer 18

make NADH for syntheses and prevent oxidative damge make sugar intermediates, especially ribose-5-phophate, nucliec acids

Question 19

pentose phophate pathway

oxidative phase?

Answer 19

Oxidative phase
==All three reactions are reversible

Glucose-6-phosphate dehydrogenase

Gluconolactonase

Phosphogluconate dehydrogenase

Question 20

pentose phosphate pathway

non oxidative phase

Answer 20

Non-oxidative phase
All reactions are reversible
Responds to needs of cell

Nucleotide biosynthesis = isomerase to ribulose-5-phosphate

Reducing power (NADPH) – recycle carbons and convert to intermediates of glycolysis

Question 21

pentose phosphate pathway

non oxidative phase

Answer 21

Non-oxidative phase
All reactions are reversible
Responds to needs of cell

Nucleotide biosynthesis = isomerase to ribulose-5-phosphate

Reducing power (NADPH) – recycle carbons and convert to intermediates of glycolysis

Question 22

regulation of glycogeneis

Alosteric regulation
1. in well fed state=?

Answer 22

In well fed state → glycogen synthase is allosterically activated by glucose 6-phosphate and ATP (in liver, not in muscle, free glucose is also an activator) → stimulates glycogenesis. In contrast, glycogen phosphorylase is allosterically inhibited by glucose 6-phosphate and ATP → no glycogenesis

Question 23

regulation of glycogenesis:

hormonal regulation=?

1. insulin
2. glucagon and epinephrine

Answer 23

1) Insulin – Insulin stimulates glycogenesis by stimulating Glycogen synthase enzyme activity.
2) Glucagon and epinephrine – Glucagon and epinephrine inhibit glycogenesis by inhibiting Glycogen synthase enzyme activity.

Question 24

regulation of glycogenesis:

hormonal regulation=?

1. insulin
2. glucagon and epinephrine

Answer 24

1) Insulin – Insulin stimulates glycogenesis by stimulating Glycogen synthase enzyme activity.
2) Glucagon and epinephrine – Glucagon and epinephrine inhibit glycogenesis by inhibiting Glycogen synthase enzyme activity.

Question 25

regulation of glycogenolysis:
alosteric regulation

1. fasting state=
2. during muscle contraction=
3. in muscles under extreme conditions of anoxia and ATP depletion=

Answer 25

) In fasting state → glycogen phosphorylase is allosterically activated by glucose 6-phosphate and ATP (in liver, not in muscle, free glucose is also an activator) → glycogenolysis. In contrast, glycogen synthase is allosterically inhibited by glucose 6-phosphate and ATP → no glycogenolysis

2) During muscle contraction → membrane depolarization occurs by nerve impulses → increase calcium concentration in muscle cell → calcium binds with calmodulin → stimulates glycogen phosphorylase → glycogenolysis.
3) In muscle under extreme conditions of anoxia and ATP depletion → increase AMP level in muscle → stimulates glycogen phosphorylase → glycogenolysis.

Question 26

regulation of glycogenolysis alosteric regulation: hormonal regulation

1. glucagon and epinphrine=

2 insulin=

Answer 26

Hormonal regulation:
1) Glucagon and epinephrine – Glucagon and epinephrine stimulate glycogenolysis by stimulating Glycogen phosphorylase enzyme activity.

2) Insulin – Insulin inhibits glycogenolysis by inhibiting Glycogen phosphorylase enzyme activity.

Question 27

_____________ and _______ help protect against ROS damage

Answer 27

superoxide dimutase and catalase