Oxidative Phosphorylation and Gluconeogenesis

Question 1

What are Km and Vmax?

Answer 1

Vmax is the maximum speed at which an enzyme can catalyze a reaction, and Km is half that.

Question 2

There are two ways that an enzyme can be chemically modified to regulate its production: ___________.

Answer 2

allosteric (non-covalent) and convalent

Question 3

What intracellular mechanism is common in the effects of fed-state hormones?

Answer 3

Insulin (the most common fed-state hormone) works by dephosphorylating enzymes.

Question 4

The counterregulatory hormones tend to work by _________.

Answer 4

phosphorylation

Question 5

What two glucose transporters do we need to know? What do they do?

Answer 5

Glut-4: insulin sensitive

Glut-2: not insulin-sensitive (it’s always there)

Question 6

What two enzymes catalyze the glucose to glucose-6-phosphate reaction?

Answer 6

Hexokinase (all other tissues)

Glucokinase (liver and beta-cell)

Question 7

Why is it important to have glucokinase in the liver?

Answer 7

Because the liver can respond to increases in glucose by increasing gluconeogenesis (which needs glucose-6-phosphate)

Question 8

What enzyme catalyzes the fructose-6-phosphate to fructose-1,6-bis-phosphate reaction?

Answer 8

Phosphofructokinase

Question 9

What things negatively and positively regulate the activity of phosphofructokinase?

Answer 9

Negative: ATP, citrate

Positive: AMP, fructose-2,6-bis-phosphate

Question 10

What is the enzyme that catalyzes the phosphoenolpyruvate to pyruvate reaction?

Answer 10

Pyruvate kinase

Question 11

The energetics of lactate dehydrogenase is such that __________.

Answer 11

it goes both ways equally (converting pyruvate to lactate)

Question 12

What molecular product of glycolysis gets pumped into the mitochondria?

Answer 12

Pyruvate

Question 13

What negatively regulates the enzyme pyruvate dehydrogenase?

Answer 13

Acetyl co-a

ATP

NADH

Question 14

True or false: the rate-limiting step in the TCA cycle is the conversion of fumarate to malate.

Answer 14

False. There is no rate-limiting step in the TCA cycle.

Question 15

The electron transport chain is linked to the TCA at _______________.

Answer 15

the succinate to fumarate reaction (catalyzed by succinate dehydrogenase)

Question 16

Protons come from the __________ space to the ___________ space.

Answer 16

intermembrane; mitochondrial matrix

Question 17

NADH delivers its electron to ______________ and becomes NAD+.

Answer 17

complex I

Question 18

______________ acts as an electron shuttle that brings electrons from complex I to complex III.

Answer 18

Coenzyme Q

Question 19

The movement of electrons through the electron transport chain stimulates _____________.

Answer 19

proton movement into the intermembrane space

Question 20

______________ accounts for a major portion of the oxygen consumption at rest –the basal metabolic rate.

Answer 20

Inherent proton leak

This can also generate heat. Brown adipose tissue utilizes this to generate heat.

Question 21

___________ accelerates electron flow.

Answer 21

ATP demand

Question 22

In a setting with a lot of ___________, gluconeogenesis can occur.

Answer 22

lactate (which can convert to pyruvate)

Question 23

Pyruvate, in order to start gluconeogenesis, gets converted to _______________.

Answer 23

oxaloacetate, then malate –which gets moved out of the mitochondria –then converted back to oxaloacetate and then phosphoenolpyruvate

Question 24

The enzyme ______________ is only present in the liver and kidneys. What does it do?

Answer 24

glucose-6-phosphatase; it removes the phosphate from glucose-6-phosphate, allowing the gluconeogenesis to send glucose into the circulation

Question 25

The only energy source for RBCs is _____________.

Answer 25

glycolysis

Question 26

RBCs send out their metabolic product as ______________.

Answer 26

lactate

Question 27

_____________ catalyzes the conversion of pyruvate to oxaloacetate.

Answer 27

Pyruvate carboxylase (uses 2 ATP –one per pyruvate); this works by charging a molecule of CO2 to a biotin prosthetic group and then transferring that CO2 to pyruvate to generate oxaloacetate.

Question 28

_____________ converts oxaloacetate to phosphoenolpyruvate.

Answer 28

Phosphoenolpyruvate carboxykinase (PEP CK) (uses 2 GTP –one per oxaloacetate)

Question 29

_____________ converts the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate.

Answer 29

Fructose 1,6-bisphosphatase

Question 30

Those without ______________ will become extremely hypoglycemic after three or four hours without food.

Answer 30

glucose-6-phosphatase

Question 31

List the pathway for glycogen synthesis.

Answer 31

Glucose
Glucose 6-phosphate
Glucose 1-phosphate 
UDP-glucose
(Glycogen synthase) *** key regulating enzyme
Glycogen

Question 32

List the breakdown pathway for glycogen.

Answer 32

Glycogen
(Glycogen phosphorylase) 
Glucose 1-phosphate 
Glucose 6-phosphate 
(Glucose 6-phosphatase) 
Glucose

Question 33

Glycogen branching is accomplished by ____________.

Answer 33

4,6-transferase

Question 34

____________ strongly stimulates glycogen phosphorylase.

Answer 34

Calcium (because it signals use)

Question 35

The proton gradient is generated by complexes __________.

Answer 35

I, III, and IV

Question 36

ATP synthase is also known as ____________.

Answer 36

complex V

Question 37

ATP synthesis is inhibited by the drug ______________.

Answer 37

oligomycin

Question 38

ATP synthase accounts for about ________ of the 36 molecules of ATP made by the oxidation of one molecule of glucose.

Answer 38

30

Question 39

One NADH can yield _____ ATP from the ETC, while one FADH2 can only yield _______ molecules of ATP.

Answer 39

2.5; 1.5

Question 40

True or false: glycerol enters gluconeogenesis in the TCA cycle.

Answer 40

False. It enters it “halfway up” gluconeogenesis (above PEP)

Question 41

Oxidation of fatty acids provides ________________.

Answer 41

ATP that can be used in gluconeogenesis

Question 42

What are the three key reactions in gluconeogenesis?

Answer 42

Pyruvate to PEP
(Pyruvate carboxylase and then phosphoenolpyruvate carboxykinase)
Fructose 1,6-bisphosphate to fructose 6-phosphate
(Fructose 1,6-bisphosphatase)
Glucose 6-phosphate to glucose
(Glucose 6-phosphatase)

Question 43

Oxaloacetate must be converted to ___________ in order to exit the mitochondrion.

Answer 43

malate by malate dehydrogenase (it gets converted back to oxaloacetate in the cytosol so that PEP CK can convert it to PEP)

Question 44

The key regulator of fructose 1,6-bisphosphatase is _____________.

Answer 44

fructose 2,6-bisphosphate (the same molecule that regulates PFK-1 in glycolysis)

Question 45

Autosomal recessive defects in _____________ (called Von Gierke’s disease) result in enlarged kidneys and liver along with hypoglycemia during fasting.

Answer 45

glucose 6-phosphatase

Question 46

True or false: 4 ATP molecules are needed to convert 2 pyruvates to 2 PEPs.

Answer 46

False. Two GTPs are needed (one per molecule) and two ATPs.

Question 47

Increased levels of ___________ in the liver stimulate pyruvate carboxylase to initiate gluconeogenesis.

Answer 47

acetyl co-a

Question 48

What is the regulated enzyme in glycogen breakdown?

Answer 48

Glycogen phosphorylase (inhibited by G6P, glucose, and ATP; stimulated by AMP and Ca in muscle –both signs of increased energy use)

Question 49

Glycogen phosphorylase is ___________ when phosphorylated.

Answer 49

activated (think about it –you want this on when glucagon is present)

Question 50

Glycogen phosphorylase kinase is ____________ when phosphorylated.

Answer 50

activated (again, you want this on when glucagon has stimulated the cell)

Question 51

Glycogen synthase is active when _____________.

Answer 51

dephosphorylated