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Biochemistry > Chapter 15 > Flashcards

Chapter 15 Flashcards

1
Q

Homeostasis occurs when

A

concentration of metabolites are kept at a steady state in the body - cannot have equilibrium without steady state

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2
Q

High ______ concentrations inhibit the committed step of glycolysis to prevent excess glucose degradation

A

ATP

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3
Q

______ inhibits the pentose phosphate pathway from committing substrates to glycolysis

A

NADPH

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4
Q

________ inhibits most hexokinases

A

Glucose-6-phosphate

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5
Q

4 ways activity of enzymes can be activated

A
  1. the concentration of substrate
  2. the presence of allosteric effectors
  3. covalent modifications
  4. binding of regulatory proteins
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6
Q

Enzymes are commonly regulated at the level of _________ and by both allosteric and covalent mechanisms

A

regulated at the level of TRANSCRIPTION

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7
Q

3 things that affect the rates of biochemical reactions

A
  1. Concentration of reactants
    Rate = k[reactants]
  2. activity of the catalyst
    the concentration of the enzyme & intrinsic activity of the enzyme
  3. Concentration of effectors
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8
Q

3 ways to speed up reaction rate

A

catalysts, increased reactants, changing temperature

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9
Q

The initial rate of the reaction is half-max when?

A

[S]=KM

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10
Q

phosphorylation is catalyzed by….?

A

protein kinases

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11
Q

Dephosphorylation is catalyzed by….?

A

protein phosphatases

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12
Q

Typically proteins are phosphorylated on the hydroxyl groups of ______,_____,______

A

Ser, Thr, Tyr

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13
Q

Metabolic ________ serves to maintain homeostasis at the molecular level

A

metabolic regulation

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14
Q

Metabolic _______ leads to a change in the output of a metabolic pathway over time

A

metabolic controls

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15
Q

AMP-activated protein kinase (AMPK) increases what things?

A

AMPK increases:
- nutrient intake in the brain
- glycolysis and fatty acid oxidation
- glucose uptake

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16
Q

AMPK Inhibits what

A

AMPK inhibits:
- insulin secretion
-fatty acid synthesis
- glycogen synthesis

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17
Q

Glycogen, a polymeric storage form of glucose in animals, is primarily found in the _____&_____

A

primarily found in the muscle and liver

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18
Q

What is the synthesis of glycogen?

A

glycogenesis

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19
Q

What is the breakdown of cellular glycogen to glucose-1-phosphate ?

A

glycogenolysis

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20
Q

Glucose linkage

A

alpha 1- 4 linkage

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21
Q

Glucose branches

A

alpha 1-6 branches every

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22
Q

Glucose 1-phosphate must be isomerized to ______ before being used in further metabolic reactions

A

Glucose-6-phosphate

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23
Q

What enzyme performs the isomerization of glucose 1-phosphate to glucose-6-phosphate

A

Phosphaglucomutase

24
Q

Sources of glucose 6-phosphate

A
  • hexokinase isozymes derive glucose-6-phosphate from glucose

-lactate taken up by liver is converted to glucose-6-phosphate by gluconeogenesis

25
Q

Glucose-6-phosphate is converted to glucose-1-phosphate by ______ to create UDP-glucose in glycogen synthesis

A

PHOSPHOGLUCOMUTASE

26
Q

What substrate serves as the primer for glycogen synthesis

A

glycogenin

27
Q

What stimulates the conversion of phosphorylase b into a?

A
  • epinephrine from vigorous muscle activity
  • glucagon in the liver
28
Q

Glycogen is degraded to glucose units for use in _________

A

energy production

29
Q

Glycogen can be made from what two things

A
  • excess blood glucose or the recycling of glucogenic metabolites like lactate or certain amino acids
30
Q

Compounds in which the anomeric carbon of a sugar is activated by attachment to a nucleotide via a phosphate ester linkage

A

sugar nucleotides

31
Q

What makes UDP-Glucose suitable for biosynthetic reactions?

A
  • UDP glucose formation is metabolically irreversible
  • the nucleotide moiety has many groups that can undergo noncovalent interactions with enzymes
  • the nucleotidy group (UDP,ADP) is a good LG
32
Q

The formation of sugar nucleotides is (endergonic/exergonic)?

A

exergonic, -delta G

33
Q

What molecule converts glycogen synthase a to synthase b by adding phosphoryl groups to three serine residues on synthase a

A

GSK3 (Glycogen synthase kinase 3)

34
Q

What molecule inactivates glycogen synthase kinase 3 (GSK3)?

A

Insulin

35
Q

What form of glycogen synthase is unphosphorylated and catalytically active?

A

glycogen synthase A

36
Q

What form of glycogen synthase is phosphorylated and inactive?

A

glycogen synthase B

37
Q

Glycogen synthase is regulated by _____?____

A

phosphorylation

38
Q

When a muscle returns to rest, what is the role of protein phosphatase 1 (PP1)?

A

PP1 removes the phosphoryl group from phosphorylase a, converting it to phosphorylase b (less active)

39
Q

What molecule is activated by insulin and leads to an increase of glycogen synthesis?

A

PP1 (protein phospatase 1)

40
Q

What must happen before glycogen synthase kinase 3 (GSK3) can phosphorylate glycogen synthase?

A

Casein Kinase II (CKII) must first phosphorylate the glycogen synthase on a nearby residue

41
Q

Why can gluconeogenesis not occur in skeletal muscle?

A

B/c skeletal muscle lacks the enzymatic machinery for gluconeogenesis

42
Q

Glycogen synthesis and degradation is regulated by what hormones?

A

insulin, epinephrine and glucagon

43
Q

Glycogen breakdown is catalyzed by?

A

glycogen phosphorylase

44
Q

Glycogen phosphorylase requires what cofactor in the phosphorolysis reaction?

A

PYRIDOXAL PHOSPHATE (PLP) which promotes attack by Pi

45
Q

End product of glycogen phosphorylase reaction?

A

Glucose 1-phosphate

46
Q

What must glucose-6-phosphate be hydrolyzed into in order to be released in the blood when blood glucose levels drop

A

To enter the blood, it gets hydrolyzed into glucose + Pi

47
Q

What enzyme catalyzes the hydrolysis of glucose-6-phosphate to glucose+Pi?

A

glucose-6-phosphatASE

48
Q

Where is the active site for the enzyme glucose-6-phosphatase?

A

on the lumenal side of the ER

49
Q

Why might glucose-6-phosphatases active site be located in the lumen?

A

This allows the cell to separate the rxn from glycolysis (which occurs in the cytosol)

50
Q

Phosphatases are what kinds of enzymes?

A

Hydrolytic

51
Q

How does AMPK respond to a decrease in the ATP/AMP ratio?

A

by phosphorylating key proteins and regulating their activities

52
Q

What is AMPK regulated (increased) by?

A

Sympathetic nervous system (fight or flight)
exercise
hormones (leptin, adiponectin)

53
Q

Glycogen is stored as cytosolic granules called?

A

Beta granules. B-granules cluster to form alpha granules

54
Q

Which type of glycogen storage granule releases glucose faster

A

The beta granules. Alpha granules are larger and release glucose slower

55
Q

Biological purpose for having many non-reducing ends?

A

increasing the number of non-reducing ends increases the number of sites available for glycogen phosphorylase & glycogen synthase

Biochemistry (10 decks)

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