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Metabolism > #7 > Flashcards

#7 Flashcards

1
Q

Lactate metabolism: lactate produced by hardworking muscle can only be converted to ____ (____)

A

pyruvate, (LDH)

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2
Q

When lactate leaves the muscle fiber where does it diffuse to?
Is this with or against its concentration gradient?

A

Extracellular fluid and into the bloodstream
down its concentration gradient

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3
Q

What is lactate efflux facilitated by?
Where does this occur?

A

monocarboxylate transporters (MCT)
on sarcolemma and t-tubule membrane

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4
Q

MCTs can also transport what? Such as?

A

other monocarboxylates (i.e. pyruvate)

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5
Q

MCT carry one ____ and one ____ in the same direction
What does this lower?
What MCTs are being used for this?

A

lactate and H+
lowers cytosolic [H+]
MCT1 AND MCT4

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6
Q

Once it’s in the blood where can lactate enter?
Here, is its concentration lower or higher than in the blood?
Is it going up or down its concentration gradient?

A

other organs
lower
down its concentration gradient

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7
Q

What organs can lactate enter once it’s in the blood?

A

Skeletal muscle (that did not participate in the exercise), heart, liver, brain, and kidney to a lesser extent

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8
Q

Cell-cell lactate shuttle: Lactate produced in some ____ such as ____ fibers, diffuses or is transported into ____ fibers and converted to ____

A

skeletal muscle, IIb fibers, I fibers, pyruvate

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9
Q

Cell-cell lactate shuttle: What two things can happen with lactate/where can it go?

A

shuttled directly to adjacent fiber or recirculated through the blood

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10
Q

Lactate in circulation can also be taken up by ____ and converted to ____

A

the heart, pyruvate

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11
Q

Lactate may also be taken up by ____ and utilized (____) or converted to another metabolite (i.e. ____-____)

A

the liver, oxidative metabolism, glucose - gluconeogenesis

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12
Q

What happens in the Cori cycle?
____ formed in ____ can ____ to the ____ where it can ____ to ____

A

lactate or pyruvate, muscle, circulate, liver, be synthesized, glucose

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13
Q

Glucose formed in the Cori cycle can then enter what?

A

the circulation

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14
Q

Intracellular lactate shuttle: mitochondria in skeletal muscle, heart, liver, other cells contain ____

A

lactate dehydrogenase

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15
Q

Some have reported that mitochondria isolated from liver, heart, and skeletal muscle ____
Possibly at greater rates than ____

A

oxidize lactate
Pyruvate

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16
Q

Rather than lactate being a dead end metabolite formed as a result of O2 deficiency, it may be ____

A

more of a link between anaerobic and aerobic metabolism than pyruvate

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17
Q

How is lactate transported into the mitochondia?

A

MCT

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18
Q

Mitochondrial lactate shuttling may also be used similarly to the ____ shuttle and ____ shuttle

A

malate-aspartate, glycerol-phosphate

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19
Q

NADH equivalent potential energy is transported to the mitochondria using a mechanism for which ____
____ for lactate
Recall that ____ and ____ do not easily diffuse across mito membranes

A

there is already a specific mitochondrial carrier
MCT
NADH, NAD+

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20
Q

What is gluconeogenesis?

A

the synthesis of glucose from compounds that are not carbohydrates

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21
Q

What is used in gluconeogenesis?

A

pyruvate, lactate, glycerol, most amino acids

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22
Q

What type of acids are pyruvate and lactate?

A

carboxylic acids

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23
Q

What does glucose synthesis from pyruvate (or lactate that has been converted to pyruvate) involve?

A

the reversal of seven of the 10 steps in glycolysis

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24
Q

What 3 reactions of glycolysis are not involved in gluconeogenesis?

A

1: hexokinase, 3: phosphofructokinase, 10: pyruvate kinase

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25
Q

Where does gluconeogenesis primarily take place?

A

the cytosol

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26
Q

gluconeogenesis takes place primarily in the cytosol, but the pyruvate must first be converted to ____ in the ____

A

oxaloacetate in the mitochondria

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27
Q

Pyruvate is transported from ____ to mito ____

A

cytosol to mito

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28
Q

What is this reaction catalyzed by?

A

pyruvate carboxylase

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29
Q

Oxaloacetate is reversibly reduced to ____
What is this reaction catalyzed by?

A

malate, mitochondrial malate dehydrogenase

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30
Q

____ then leaves the mitochondria via ____ shuttle

A

malate aspartate

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31
Q

Malate is then reoxidized in cytosol to ____. This produces ____
What is this reaction catalyzed by?

A

oxaloacetate, cytosolic
cytosolic malate dehydrogenase

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32
Q

Oxaloacetate is then converted to ____
What is this reaction catalyzed by?

A

phosphoenolpyruvate
PHOSPHOENOLPYRUVATE CARBOXYKINASE

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33
Q

Conversion of fructose 1,6 biphosphate into ____
Promotes irreversible hydrolysis of the ____

A

fructose 6 phosphate
carbon-1 phosphate

34
Q

Conversion of glucose-6-phosphate into ____
This is the ___ bypass
What type of reaction is this?
____ of glucose-6-phosphate

A

glucose
3rd
final reaction
dephosphorylation

35
Q

What are the main animal organs where gluconeogenesis takes place?

A

liver and kidneys

36
Q

What does muscle lack? What does this mean about its ability to convert pyruvate and lactate?

A

glucose-6-phosphate
IT cannot convert pyruvate and lactate directly to glucose

37
Q

Where can pyruvate and lactate be converted to glucose-6-phosphate? What can it then be converted to?

A

muscle, glycogen

38
Q

In glycogenesis what is the link between glucose-6-phosphate and glycogen?

A

glucose-1-phosphate

39
Q

In glycogenesis what is the link between glucose-6-phosphate and pyruvate?

A

fructose-6-phosphate

40
Q

In glycogenesis what is the link between glucose-6-phosphate and ribose-5-phosphate?

A

6-phosphogluconate

41
Q

What is glycogenesis?

A

glycogen synthesis

42
Q

Glucose entering ____ (__) or ____ can be involved in glycogenesis

A

liver (hepatocytes) or muscle fibers

43
Q

Where does glycogen serve as a reservoir of glucose?
Readily converted to ____ for distribution to other tissues

A

liver
blood glucose

44
Q

Where is glycogen broken down via glycolysis to
provide ATP for muscle contraction?

A

muscle

45
Q

What is the protein in the glycogen core?

A

glycogenin protein

46
Q

Glycogenin acts as the primer to which ____

A

the first glucose residue is attached

47
Q

Glycogenin is the catalyst for synthesis of developing ____

A

glycogen molecule

48
Q

Successive addition of ____ units to a growing chain
What is the catalyst for this
Requires energy input (____)
One ____ and one ____ (____) per glucose added

A

glucosyl
glycogen synthase
biosynthetic process
ATP, UTP, uridine triphosphate

49
Q

What is the starting point for glycogenesis?

A

glucose-6-phosphate

50
Q

What happens to much of the glucose ingested during a meal?

A

It takes a roundabout path to glycogen

51
Q

First taken up by ____ in bloodstream and converted to ____

A

erythrocytes, lactate

52
Q

Lactate is then taken up by the liver and converted to ____ by gluconeogenesis

A

glucose-6-phosphate

53
Q

To initiate glycogen synthesis, glucose-6-phosphate is reversible converted to ____
What is this reaction catalyzed by?

A

glucose-1-phosphate
Phosphoglucomutase

54
Q

What is then formed?
What is this catalyzed by?
What type of reaction is this?

A

UDP-glucose
UDP-GLUCOSE PYROPHOS-PHORYLASE
key reaction in glycogenesis

55
Q

This reaction proceeds in the direction of UDP-glucose formation because ____ is rapidly hydrolyzed by ____

A

pyrophosphate
inorganic pyrophosphate

56
Q

UDP-Glucose is the immediate donor of ___ residues in the formation of ___ by the action of ___

A

glucose, glycogen, glycogen synthase

57
Q

Promotes the transfer of the ____ residue from UDP-glucose to the ____ of the branched ____ molecule

A

glucosyl, non reducing end, glycogen

58
Q

What kind of chains does glycogen synthesis create?

A

linear chains

59
Q

What is needed to form branches of glucosyl chains?

A

branching enzyme

60
Q

What does this branching enzyme do when in detaches segments of the existing chain?

A

transfers it to the interior

61
Q

What is glycogenolysis?

A

degradation of glycogen

62
Q

What is glycogenolysis catalyzed by?

A

glycogen phosphorylase or phosphorylase

63
Q

What’s different about phosphorylase? It cannot completely ____

A

catalyze the breaking of bonds in glycogen

64
Q

What is phosphorylase unable to remove?

A

glucosyl units lying four or fewer places away
from a branch point

65
Q

When the chain becomes less than 4 units what happens?

A

another enzyme is involved

66
Q

Debranching enzyme catalyzes 2 reactions: Transport of what and removal of what?

A

Transport of three out of the four glucosyl units of a
branch to the end of another
Removal of the remaining unit by hydrolysis of it
particular glycosidic linkage (α1→6)

67
Q

After the previous reaction the branch is eliminated which then allows ____ to catalyze the reaction

A

glycogen phosphorylase

68
Q

Glycogen phosphorylase allows for the release of
molecules of ____. What are these produced?

A

glucose-1-phosphate, produced until the enzyme is four glucosyl units away from the next branch

69
Q

What will debranching enzyme do next?

A

Eliminate the branch (and so on and so on)

70
Q

Glucose-1-phosphate is converted into ____ by ____

A

glucose-6-phosphate by phosphoglucomutase

71
Q

Where is pathway activity low and high?

A

low in skeletal muscle and high in adipose tissue

72
Q

____ needed in adipose tissue to
synthesize ____ from Acetyl-CoA

A

NADPH, FA

73
Q

What controls pathway at the first step?

A

NADPH

74
Q

High NADPH/NADP ratio inhibits ____

A

glucose-6-phosphate dehydrogenase

75
Q

What does high NADPH/NADP and NAD/NADH ratios at same time mean?

A

biosynthesis and glycolysis can occur at same time at high rates

76
Q

Because no ATP is required what can happen?

A

it can continue anaerobically

77
Q

Ribulose 5-phosphate can be converted to ____ and/or down the pathway

A

Ribose 5-phosphate

78
Q

Generation of ____ for biosynthesis of ____,
Cholesterol (steroids)

A

NADPH, FA

79
Q

What is the formation of ribose-5-phosphate used for?

A

The synthesis of nucleosides (ATP, CoA, NAD, FAD,NADP, RNA, DNA)

80
Q

Yield ____ and ____ for
glycolysis or for more G 6-P to enter Pentose

A

2 Fructose 6-P and 1 glyceraldehyde 3-P

81
Q

Phosphate pathway for ____ (____)

A

NADPH (reversible reaction or gluconeogenesis)

82
Q

In the pentose phosphate pathway what does the flow of glucose-6-phospate depend on?

A

the need for NADPH, ribose-5-phosphate, and ATP

Metabolism (6 decks)

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