Pentose Phosphate shunt and Gluconeogenesis - CB

Question 1

Where are the enzymes found for the pentose P shunt?

Answer 1

Cytosol

Question 2

What are the products of the Pentose P shunt?

Answer 2

NADPH and ribose-5-phosphate (R5P)

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

Question 3

What phase of the pentose P shunt are irreversible?

Answer 3

Oxidative phase: first 3 reactions

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

Question 4

what reactions produce NADPH in the pentose P shunt?

Answer 4

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

Question 5

Are the nonoxidative steps of the pentose P shunt reversible?

Answer 5

yes

Question 6

What prosthetic group is in transketolase?

Answer 6

TPP

Question 7

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

Answer 7

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

Question 8

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

Answer 8

2

Question 9

Are enzymes specific to NAD+ or NADP+?

Answer 9

Yes, many are specific to only one

Question 10

What tissues use the pentose phosphate pathway? functions?

Answer 10

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)

Question 11

Main uses of NADPH (general)?

Answer 11

biosynthesis and detoxification?

Question 12

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

Answer 12

Favism (hemolytic anemia)

however, advantage against malaria

Question 13

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

Answer 13

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

Question 14

what are the biosynthetic uses of ribose?

Answer 14

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

Question 15

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

Answer 15

Liver and a small amount in the kidney

gluconeogenesis

Question 16

What is the primary fuel in the brain and RBCs?

Answer 16

Glucose

Question 17

Where is glycogen broken down during fasting and why?

Answer 17

Liver, to maintain blood glucose

Question 18

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

Answer 18

gluconeogenesis

Question 19

what are the substrates of gluconeogenesis?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

Only Amino acids not capable to contributing to gluconeogenesis?

Answer 23

Leu and lys

Question 24

Can acetyl-CoA contributing to gluconeogenesis?

Answer 24

NOPE

Question 25

Where does gluconeo start?

Answer 25

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

Question 26

Is Figure 20-13 Important?

Answer 26

No clue seems like BS to me

Question 27

Is there a transport system for oxaloacetate?

Answer 27

Nope, but can use Mal/Asp shuttle in reverse

Question 28

Is there a transport system for PEP?

Answer 28

Yep oddly named the PEP transporter

Question 29

energy costs of gluconeogenesis?

Answer 29

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)

Question 30

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

Answer 30

Cori

Question 31

What is the "Oxygen Debt"?

Answer 31

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

Question 32

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

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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)

Question 35

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

Answer 35

Throw something at Itamar if he's within range

Question 36

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

Answer 36

Watch the "CHEETO Schiedo" Video