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Biochemistry > Chapter 15 > Flashcards

Chapter 15 Flashcards

(55 cards)

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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

Study These Flashcards
A

Phosphaglucomutase

24
Q

Sources of glucose 6-phosphate

Study These Flashcards
A
  • hexokinase isozymes derive glucose-6-phosphate from glucose

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

25
Glucose-6-phosphate is converted to glucose-1-phosphate by ______ to create UDP-glucose in glycogen synthesis
PHOSPHOGLUCOMUTASE
26
What substrate serves as the primer for glycogen synthesis
glycogenin
27
What stimulates the conversion of phosphorylase b into a?
- epinephrine from vigorous muscle activity - glucagon in the liver
28
Glycogen is degraded to glucose units for use in _________
energy production
29
Glycogen can be made from what two things
- excess blood glucose or the recycling of glucogenic metabolites like lactate or certain amino acids
30
Compounds in which the anomeric carbon of a sugar is activated by attachment to a nucleotide via a phosphate ester linkage
sugar nucleotides
31
What makes UDP-Glucose suitable for biosynthetic reactions?
- 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
The formation of sugar nucleotides is (endergonic/exergonic)?
exergonic, -delta G
33
What molecule converts glycogen synthase a to synthase b by adding phosphoryl groups to three serine residues on synthase a
GSK3 (Glycogen synthase kinase 3)
34
What molecule inactivates glycogen synthase kinase 3 (GSK3)?
Insulin
35
What form of glycogen synthase is unphosphorylated and catalytically active?
glycogen synthase A
36
What form of glycogen synthase is phosphorylated and inactive?
glycogen synthase B
37
Glycogen synthase is regulated by _____?____
phosphorylation
38
When a muscle returns to rest, what is the role of protein phosphatase 1 (PP1)?
PP1 removes the phosphoryl group from phosphorylase a, converting it to phosphorylase b (less active)
39
What molecule is activated by insulin and leads to an increase of glycogen synthesis?
PP1 (protein phospatase 1)
40
What must happen before glycogen synthase kinase 3 (GSK3) can phosphorylate glycogen synthase?
Casein Kinase II (CKII) must first phosphorylate the glycogen synthase on a nearby residue
41
Why can gluconeogenesis not occur in skeletal muscle?
B/c skeletal muscle lacks the enzymatic machinery for gluconeogenesis
42
Glycogen synthesis and degradation is regulated by what hormones?
insulin, epinephrine and glucagon
43
Glycogen breakdown is catalyzed by?
glycogen phosphorylase
44
Glycogen phosphorylase requires what cofactor in the phosphorolysis reaction?
PYRIDOXAL PHOSPHATE (PLP) which promotes attack by Pi
45
End product of glycogen phosphorylase reaction?
Glucose 1-phosphate
46
What must glucose-6-phosphate be hydrolyzed into in order to be released in the blood when blood glucose levels drop
To enter the blood, it gets hydrolyzed into glucose + Pi
47
What enzyme catalyzes the hydrolysis of glucose-6-phosphate to glucose+Pi?
glucose-6-phosphatASE
48
Where is the active site for the enzyme glucose-6-phosphatase?
on the lumenal side of the ER
49
Why might glucose-6-phosphatases active site be located in the lumen?
This allows the cell to separate the rxn from glycolysis (which occurs in the cytosol)
50
Phosphatases are what kinds of enzymes?
Hydrolytic
51
How does AMPK respond to a decrease in the ATP/AMP ratio?
by phosphorylating key proteins and regulating their activities
52
What is AMPK regulated (increased) by?
Sympathetic nervous system (fight or flight) exercise hormones (leptin, adiponectin)
53
Glycogen is stored as cytosolic granules called?
Beta granules. B-granules cluster to form alpha granules
54
Which type of glycogen storage granule releases glucose faster
The beta granules. Alpha granules are larger and release glucose slower
55
Biological purpose for having many non-reducing ends?
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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