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U6 MCP > Pentose Phosphate shunt and Gluconeogenesis - CB > Flashcards

Pentose Phosphate shunt and Gluconeogenesis - CB Flashcards

1
Q

Where are the enzymes found for the pentose P shunt?

A

Cytosol

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2
Q

What are the products of the Pentose P shunt?

A

NADPH and ribose-5-phosphate (R5P)

R5P is converted to fructose 6 Phosphate and glyceraldehyde-3-phosphate during the nonoxidative steps

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3
Q

What phase of the pentose P shunt are irreversible?

A

Oxidative phase: first 3 reactions

enzymes: 1. G6P dehydrogenase
2. 6-phospho-glucono-lactonase
3. 6-phospho-gluconate dehydrogenase

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4
Q

what reactions produce NADPH in the pentose P shunt?

A

Oxidative phase: reactions 1 and 3
G6P dehydrogenase
6-phospho-gluconate dehydrogenase

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5
Q

Are the nonoxidative steps of the pentose P shunt reversible?

A

yes

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6
Q

What prosthetic group is in transketolase?

A

TPP

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7
Q

What is the purpose of the nonoxidative reactions of the pentose P shunt?

A

To convert Ribulose-5-Phosphate into intermediates of the glycolytic pathway

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8
Q

how many NADPH are produced per glucose in the pentose phosphate shunt?

A

2

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9
Q

Are enzymes specific to NAD+ or NADP+?

A

Yes, many are specific to only one

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10
Q

What tissues use the pentose phosphate pathway? functions?

A

Adrenal gland: steroid syn
Testes/ovaries: steroid syn
Liver: cholesterol and fatty acid syn
adipose tissue: fatty acid syn
mammary gland: fatty acid syn
Sm intestine: detoxify xenobiotics (cytochrome P450)
RBC: detoxify reactive oxygen species (glutathione reductase)

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11
Q

Main uses of NADPH (general)?

A

biosynthesis and detoxification?

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12
Q

what are the consequences of a glucose-6-phosphate dehydrogenase (G6PDH) deficiency?

A

Favism (hemolytic anemia)

however, advantage against malaria

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13
Q

What happens if we only need more ribose-5-phosphate and not NADPH

A

nonoxidative pathway in reverse: fructose-6-P (F6P) + gylceraldehyde phosphate (GAP)»> ribose-5-phosphate

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14
Q

what are the biosynthetic uses of ribose?

A 
RNA/DNA
NTPs
NADH/FADH
CoA
In general: information storage, energy transfer, oxidation/reduction reactions, and enzyme catalysis
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15
Q

Where is glucose-6-phosphatase located and what is it used for?

A

Liver and a small amount in the kidney

gluconeogenesis

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16
Q

What is the primary fuel in the brain and RBCs?

A

Glucose

17
Q

Where is glycogen broken down during fasting and why?

A

Liver, to maintain blood glucose

18
Q

What system/process takes over when glycogen is depleted to maintain blood glucose?

A

gluconeogenesis

19
Q

what are the substrates of gluconeogenesis?

A

lactate, pyruvate, CAC intermediates, amino acids (except Leu and Lys)

20
Q

What reactions of glycolysis are irreverable and must be bypassed in gluconeogenesis?

A

THIS INFO IS SHITTY BUT PROLLY IMPORTANT:
Glucose->Glucose6P (via hexokinase) bypassed (bypass 3)) in opposite direction with glucose-6-phosphatase

Fructose-6P->Fructose-1,6-BP (via phosphofructokinase (PFK)) bypassed (bypass2) in opposite direction with fructose bis-phosphatase

phosphoenolpyruvate (PEP) -> pyruvate (via pyruvate kinase bypassed (bypass1) by 2 reactions:
pyrvate -> (via pyruvate carboxylase)-> oxaloacetate ->(via PEPcarboxykinase)-> PEP

21
Q

where is the only place pyruvate carboxylase (gluconeo) is found? what does it do? what is the cofactor? any energy spent?

A

Mitochondria, adds COO to CH3 of pyruvate (making oxaloacetate), biotin, 1 ATP per rxn used 1CO2

22
Q

What are the subsrates and products for PEPcarboxykinase (gluconeo)?

A

Substrates: oxaloacetate, GTP
Products: GDP, PEP (phosphoenolpyruvate), CO2

23
Q

Only Amino acids not capable to contributing to gluconeogenesis?

A

Leu and lys

24
Q

Can acetyl-CoA contributing to gluconeogenesis?

A

NOPE

25
Q

Where does gluconeo start?

A

mitochondria ( minor exception: glycerol is converted to DHAP in cytosol)

26
Q

Is Figure 20-13 Important?

A

No clue seems like BS to me

27
Q

Is there a transport system for oxaloacetate?

A

Nope, but can use Mal/Asp shuttle in reverse

28
Q

Is there a transport system for PEP?

A

Yep oddly named the PEP transporter

29
Q

energy costs of gluconeogenesis?

A

6 ATP (really 4ATP and 2GTP) per molecule of glucose made

Bypass 1 (pyruvate carboxylase and PEPCK): 2ATP and 2 GTP respectively

Phosphoglycerate kinase reaction used 2 ATP in gluconeo (produced 2 in glycolysis)

30
Q

The balance between liver and muscle glucose, glycogen, and lactate levels is called the _______ cycle.

A

Cori

31
Q

What is the “Oxygen Debt”?

A

the amount of O2 consumed in liver during its replenishing of the muscle glycogen supply

32
Q

Enzymes used in both glycolysis and gluconeogenesis? enzymes unique to each?

A

BOTH: enolase, phosphoglycerate mutate, phsphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase, Triose phosphate isomerase, aldolase, phosphoglucose isomerase

ONLY glycolysis: pyruvate kinase, phosphofructokinase, or hexokinase

ONLY gluconeogenesis: pyruvate carboxylase PEPcarboxykinase, fructose bis-phosphatase, glucose-6-phosphatase

33
Q

Oxidative Phase if Pentose P shunt enzymes and the type of reaction they catalyze?

A

Glucose-6P dehydrogenase: oxidation (Produces NADPH)
6-phosphoglucono lactonase: hydrolysis
6-phosphogluconate dehydrogenase: oxidation/decarboxylation (produced NADPH)

34
Q

Non Oxidative Phase if Pentose P shunt enzymes and the type of reaction they catalyze?

A

Ribulose-5-P isomerase: isomerization
Ribulose-5-p epimerase: epimerization
Transketolase (3 rxns): intermolecular transfer of a C2 unit (dihydroxyethyl) then intermolecular transfer of a C3 unit (dihydroxyacetone) than another intermolecular transfer of a C2 unit (dihydroxyethyl)

35
Q

Stare at Figure 15-23 (pg 105 of PDF) for 5 min

A

Throw something at Itamar if he’s within range

36
Q

Stare at Figure 14-30 (pg 94 of PDF) for 5 min

A

Watch the “CHEETO Schiedo” Video

U6 MCP (26 decks)

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