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BCMB > week 7 > Flashcards

week 7 Flashcards

1
Q

metabolically irreversible and regulated steps in glycolysis

A 
#1 (hexokinase)	
#3 (phosphofructokinase)	
#10 (pyruvate kinase)
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2
Q

Gluconeogenesis irreversible step enzymes

A

Phosphatase enzymes
Pyruvate kinase-Pyruvate carboxylase /
PEP carboxykinase

Phosphofructokinase - Fructose-1,6-Bisphosphatase

Hexokinase - Glucose-6-Phosphatase

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3
Q

location of gluconeogenesis

A

cytoplasm of liver and kidney cells

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4
Q

why is CO2 used in the first step of gluconeogenesis

A

to increase the entropy of the reaction and drive it forward

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5
Q

Pi

A

inorganic phosphate

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6
Q

pyruvate carboxylase

A

converts pyruvate to oxaloacetate. phosphorylates CO2 and adds it to pyruvate

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7
Q

PEP Carboxykinase

A

Conversion of oxaloacetate to PEP

GTP is hydrolyzed to provide energy and donates a phosphoryl group

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8
Q

Fructose-1,6-bisphosphatase

A

Hydrolysis of F-1,6-BP to F-6-P

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9
Q

Fructose-1,6-bisphosphatase regulation

A

Allosteric regulation:
citrate stimulates (**Why this?!)
fructose-2,6-bisphosphate inhibits
AMP inhibits (doesnt have enough energy to make glucose for the body)

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10
Q

Glucose-6-Phosphatase

A

Conversion of Glucose-6-P to Glucose

occurs in the ER of liver cells

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11
Q

Why does glucose conversion occur in the ER

A

ER vesicles filled with glucose diffuse to the plasma membrane, fuse with it and open, releasing glucose into the bloodstream.

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12
Q

Lactate Recycling

cori cycle

A

pyruvate is reduced to lactate. Lactate is then returned to the liver, where it can be reoxidized to pyruvate by liver LDH. Liver provides glucose to muscle for exercise and then reprocesses lactate into new glucose

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13
Q

Regulation of Gluconeogenesis

A

Inhibited by glycolysis

Important steps are regulated

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14
Q

Undernourished person consuming alcohol leads to…

A

hypoglycemia

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15
Q

How can alcohol cause hypoglycemia

A

Ethanol inhibits liver gluconeogenesis since the liver cannot metabolize the excess reducing equivalents (NADH) made by oxidizing ethanol. This blocks conversion of lactate to glucose, promotes conversion of alanine to lactate, can even create mild lactic acidosis

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16
Q

Glycogen

A

animal storage of glucose) is a long polymer of glucose – long chains connected by a-(1–>4) bonds, and branches connected by a-(1–>6) bonds

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17
Q

Starch

A

is the plant form of glucose storage

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18
Q

How is glycogen and starch catabolized?

A

Amylase is an endoglycosidase. It cleaves dietary amylopectin or glycogen to maltose, maltotriose and other small oligosaccharides. It is active on either side of a branch point, but activity is reduced near the branch points

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19
Q

Is tissue glycogen different from dietary glycogen?

A

Yes. Tissue glycogen’s breakdown is carefully controlled.

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20
Q

Metabolism of tissue glycogen

A

Glycogen phosphorylase cleaves glucose from the nonreducing ends of glycogen molecules
This is a phosphorolysis

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21
Q

How Is Glycogen Synthesized?

A

Glucose units are activated for transfer by formation of sugar nucleotides

22
Q

UDP-glucose pyrophosphorylase

A

driven by pyrophosphate hydrolysis.
The reaction is a phosphoanhydride exchange, with a phosphoryl oxygen of glucose-1-P attacking the a-phosphorus of UTP to form UDP-glucose and pyrophosphate.

23
Q

Glycogenin

A

a protein that forms the core of a glycogen particle

24
Q

Glycogen synthase

A

transfers glucosyl units from UDP-glucose to C-4 hydroxyl at a nonreducing end of a glycogen strand

25
Q

How Is Glycogen Metabolism Controlled

A

A highly regulated process, involving reciprocal control of glycogen phosphorylase and glycogen synthase.Both enzymes are regulated by covalent modification - phosphorylation

26
Q

Glycogen phosphorylase regulation

A

allosterically activated by AMP and inhibited by ATP, glucose-6-P and caffeine

27
Q

glycogen synthase regulation

A

is stimulated by glucose-6-P

28
Q

Glucagon and epinephrine (hormone regulation)

A

stimulate glycogen breakdown - opposite effect of insulin

29
Q

insulin (hormone regulation)

A

stimulates glycogen synthesis and inhibits glycogen breakdown

30
Q

Pentose Phosphate Pathway (PPP)

A

Provides NADPH for biosynthesis
Produces Ribose-5-P
Two oxidative processes followed by five non-oxidative steps

31
Q

PPP location

A

Operates mostly in cytoplasm of liver and adipose cells

NADPH is used in cytosol for fatty acid synthesis

32
Q

Oxidative steps of PPP

A
  1. Glucose-6-P Dehydrogenase (G6PD)*
    Irreversible 1st step - highly regulated!
  2. Gluconolactonase
    Uncatalyzed reaction happens too
  3. 6-Phosphogluconate Dehydrogenase
    An oxidative decarboxylation (in that order!)
33
Q

Non-oxidative steps

A

Makes a bunch of different types of sugars through 4 types of reactions

34
Q

Variation on the PPP depends on..

A

what product is needed at the moment. Such as ribose-5-P, NADPH, or ATP

35
Q

Central metabolism

A

glycolysis and TCA cycle

36
Q

reciprocal regulation of metabolic pathway enzymes

A 
Allosteric regulation of enzymes		(modulated)
 Covalent modification (de)phosphorylation
37
Q

metabolic processes in the cytoplasms

A

fatty acid synthesis, glycolysis, most gluconeogenesis rxns, pentose phosphate pathway

38
Q

metabolic processes in the mitochondria

A

TCA cycle, oxidative phosphorylation, fatty acid breakdown

39
Q

during glycolysis, 1 glucose gets converted into…

A

2 pyruvate molecules

40
Q

Pyruvate can be further metabolized to

A

Lactate or ethanol (anaerobic) Acetyl CoA (aerobic)

41
Q

Net ATP of glycolysis

A

2 ATP.

2 ATPs used, 4 ATPs made

42
Q

2 stages of glycolysis

A

hexose and triode stage

43
Q

3 metabolically irreversible steps of glycolysis

A
  1. Hexokinase
  2. Phosphofructokinase
  3. Pyruvate Kinase
44
Q

Hexokinase

A

phosphorylates glucose to generate glucose-6-phosphate (G6P)

45
Q

Isozyme

A

multiple forms of an enzyme

46
Q

Phosphofructokinase-1 (PFK-1)

A

Catalyzes transfer of a phosphoryl group from ATP to F6P to form fructose 1,6-bisphosphate (F1,6BP)

47
Q

phosphofructokinase-2 (PFK-2)

A

synthesizes fructose 2,6-bisphosphate (F2,6BP)

48
Q

Regulation of Phosphofructokinase-1

A

inhibited by high levels of citrate, ATP, and F2,6BP

activated by AMP

49
Q

Pyruvate Kinase (PK)

A

converts phosphoenolpyruvate (PEP) into pyruvate

50
Q

Metabolism of Pyruvate to Ethanol (yeast - anaerobic)

A

Two reactions required:

(1) Pyruvate decarboxylase
(2) Alcohol dehydrogenase

51
Q

The Pasteur Effect

A

the slowing of glycolysis in the presence of oxygen
(This is due to the fact that more ATP is produced under aerobic conditions than under anaerobic conditions, therefore less glucose is consumed aerobically )

52
Q

Reduction of Pyruvate to Lactate (muscles - anaerobic)

A

Muscle lactate dehydrogenase converts pyruvate to lactate

This reaction regenerates NAD+ for use by GAPDH in glycolysis

BCMB (8 decks)

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