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18' DEMS > 🔸Oxidative Phosphorylation and Gluconeogenesis > Flashcards

🔸Oxidative Phosphorylation and Gluconeogenesis Flashcards

1
Q

What are Km and Vmax?

A

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

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2
Q

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

A

allosteric (non-covalent) and convalent

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3
Q

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

A

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

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4
Q

The counterregulatory hormones tend to work by _________.

A

phosphorylation

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5
Q

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

A

Glut-4: insulin sensitive

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

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6
Q

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

A

Hexokinase (all other tissues)

Glucokinase (liver and beta-cell)

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7
Q

Why is it important to have glucokinase in the liver?

A

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

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8
Q

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

A

Phosphofructokinase

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9
Q

What things negatively and positively regulate the activity of phosphofructokinase?

A

Negative: ATP, citrate

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

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10
Q

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

A

Pyruvate kinase

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11
Q

The energetics of lactate dehydrogenase is such that __________.

A

it goes both ways equally (converting pyruvate to lactate)

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12
Q

What molecular product of glycolysis gets pumped into the mitochondria?

A

Pyruvate

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13
Q

What negatively regulates the enzyme pyruvate dehydrogenase?

A

Acetyl co-a
ATP
NADH

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14
Q

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

A

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

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15
Q

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

A

the succinate to fumarate reaction (catalyzed by succinate dehydrogenase)

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16
Q

Protons accumulate in the […] space and will move down their gradient to the […].

A

intermembrane; mitochondrial matrix

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17
Q

NADH delivers its electron to ______________ and becomes NAD+.

A

complex I

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18
Q

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

A

Coenzyme Q

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19
Q

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

A

proton movement into the intermembrane space

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20
Q

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

A

Inherent proton leak

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

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21
Q

___________ accelerates electron flow.

A

ATP demand

22
Q

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

A

lactate (which can convert to pyruvate)

23
Q

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

A

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

24
Q

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

A

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

25
Q

The only energy source for RBCs is _____________.

A

glycolysis

26
Q

RBCs send out their metabolic product as ______________.

A

lactate

27
Q

_____________ catalyzes the conversion of pyruvate to oxaloacetate.

A

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.

28
Q

_____________ converts oxaloacetate to phosphoenolpyruvate.

A

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

29
Q

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

A

Fructose 1,6-bisphosphatase

30
Q

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

A

glucose-6-phosphatase

31
Q

List the pathway for glycogen synthesis.

A 
Glucose
Glucose 6-phosphate
Glucose 1-phosphate 
UDP-glucose
(Glycogen synthase) *** key regulating enzyme
Glycogen
32
Q

List the breakdown pathway for glycogen.

A 
Glycogen
(Glycogen phosphorylase) 
Glucose 1-phosphate 
Glucose 6-phosphate 
(Glucose 6-phosphatase) 
Glucose
33
Q

Glycogen branching is accomplished by ____________.

A

4,6-transferase

34
Q

[…] strongly stimulates glycogen phosphorylase.

A

Calcium (because it signals use)

35
Q

The proton gradient is generated by complexes […].

A

I, III, and IV

36
Q

ATP synthase is also known as […].

A

complex V

37
Q

ATP synthesis is inhibited by the drug […].

A

oligomycin

38
Q

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

A

30

39
Q

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

A

2.5; 1.5

40
Q

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

A

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

41
Q

Oxidation of fatty acids provides ________________.

A

ATP that can be used in gluconeogenesis

42
Q

What are the three key reactions in gluconeogenesis?

A

•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)

43
Q

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

A

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

44
Q

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

A

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

45
Q

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

A

glucose 6-phosphatase

46
Q

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

A

False.

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

47
Q

Increased levels of […] in the liver stimulate pyruvate carboxylase to initiate gluconeogenesis.

A

acetyl co-a

48
Q

What is the regulated enzyme in glycogen breakdown?

A

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

49
Q

Glycogen phosphorylase is […] when phosphorylated.

A

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

50
Q

Glycogen phosphorylase kinase is […] when phosphorylated.

A

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

51
Q

Glycogen synthase is active when […].

A

dephosphorylated

18' DEMS (133 decks)

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