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diamond Flashcards

1
Q

compare and contrast GLUT2/GLUT4: important tissues

A

GLUT2: liver and pancreas
GLUT4: adipose tissue and muscle

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2
Q

compare and contrast GLUT2/GLUT4: Km

A

GLUT2: high Km (~15 mM)
GLUT4: low Km (~5 mM)

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3
Q

compare and contrast GLUT2/GLUT4: saturated at normal glucose levels?

A

GLUT2: no; cannot be saturated at normal physiological conditions
GLUT4: yes; saturated when glucose levels are only slightly above 5 mM

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4
Q

compare and contrast GLUT2/GLUT4: response to insulin?

A

GLUT2: No, but serves as glucose sensor to cause release of insulin in pancreatic B-cells
GLUT4: Yes

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5
Q

How does insulin promote glucose entry into cells?

A

GLUT4 is saturated when glucose levels are only slightly above 5 mM, so glucose entry can only be increased by increasing the number of transporters. Insulin promotes the fusion of vesicles containing preformed GLUT4 with the cell membrane

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6
Q

Hexokinase: function/regulation/reversible?

A

phosphorylates glucose to form glucose-6-phosphate, “trapping” glucose in the cell. inhibited by glucose-6-phosphate. irreversible.

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7
Q

Glucokinase: function/regulation/reversible?

A

glucokinase phosphorylates and “traps” glucose in liver and pancreatic cells, and works with GLUT2 as part of the glucose sensor in B-islet cells. In liver cells, it is induced by insulin. Irreversible.

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8
Q

Phosphofructokinase-1: function/regulation/reversible?

A

PFK-1 catalyzes RLS of glycolysis, phosphorylating fructose 6-phosphate to fructose 1,6-bisphosphate using ATP. Inhibited by ATP, citrate, glucagon. Activated by AMP, fructose 2,6-bisphospahte, insulin. Irreversible.

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9
Q

Glyceraldehyde-3-phosphate dehydrogenase: function/reversible?

A

glyceraldehyde-3-phosphate dehydrogenase generates NADH while phosphorylating glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate. Reversible.

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10
Q

3-phosphoglycerate kinase: function/reversible?

A

3-phosphoglycerate kinase performs a substrate-level phosphorylation, transferring a phosphate from 1,3-bisphosphoglycerate to ADP, forming ATP and 3-phosphoglycerate. Reversible.

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11
Q

pyruvate kinase: function/regulation/reversible?

A

pyruvate kinase performs another substrate-level phosphorylation, transferring a phosphate from PEP to ADP, forming ATP and pyruvate. It is activated by fructose 1,6-bisphosphate. Irreversible.

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12
Q

why must pyruvate undergo fermentation for glycolysis to continue?

A

fermentation must occur to regenerate NAD+, which is in limited supply in cells. fermentation generates no ATP or energy carriers; it merely regenerates the coenzymes needed in glycolysis.

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13
Q

why is it necessary that fetal hemoglobin does not bind 2,3-BPG?

A

the binding of 2,3-BPG decreases hemoglobin’s affinity for oxygen.

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14
Q

high altitude PO2

A

is lower, increase respiration

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15
Q

bisphosphoglycerate mutase

A

RBC use this enzyme to convert 1,3-BPG to 2,3-BPG, which decreases Hg’s affinity for oxygen

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16
Q

how can liver continue glycolysis in order to generate pyruvate for FA synthesis and glycogenesis in the presence of ATP?

A

PFK-2, an enzyme found mostly in liver, converts fructose 6-phosphate to F2,6-BP, which activates PFK-1

17
Q

which enzyme is responsible for trapping galactose in the cell?

A

galactokinase

18
Q

what enzyme in galactose metabolism results in a product that can feed directly into glycolysis, linking the two pathways?

A

galactose-1-phosphate uridyltransferase produces glucose 1-phosphate, a glycolytic intermediate, thus linking the pathways

19
Q

which enzyme is responsible for trapping fructose in the cell?

A

fructokinase, with a small contribution from hexokinase

20
Q

what enzyme in fructose metabolism results in a product that can feed directly into glycolysis, linking the two pathways?

A

aldolase B produces DHAP and glyceraldehyde (which can be phosphorylated to glyceraldehyde 3-phosphate), which are glycolytic intermediates, thus linking the pathways

21
Q

what are the reactants of the pyruvate dehydrogenase complex?

A

pyruvate, NAD+, CoA

22
Q

what are the products of the pyruvate dehydrogenase complex?

A

Acetyl-CoA, NADH, CO2

23
Q

how does acetyl-CoA affect PDH complex activity? why?

A

inhibits. signals cell is energetically satisfied. pyruvate can then be used to form other products, such as OAA for use in gluconeo

24
Q

what is the structure of glycogen?

A

core protein glycogenin with linear chains of glycose emanating out from center. if the chains are branched, the highest density is at periphery.

25
Q

what type of glycosidic links exist in a glycogen granule?

A

alpha-1,4 glycosidic links connect linear chains. branches are formed by alpha-1,6 glycosidic links.

26
Q

what are the two main enzymes of glycogenesis, and what does each accomplish?

A

glycogen synthase attaches the glucose molecule from UDP-glucose to the growing glycogen chain to form alpha-1,4. branching enzyme breaks an alpha-1,4 and attaches the oligoglucose as a branch by alpha-1,6.

27
Q

what are the two main enzymes of glycogenolysis, and what does each accomplish?

A

glycogen phosphorylase removes a glucose molecule from glycogen using a phosphate and creates glucose 1-phosphate.
Debranching enzyme breaks alpha-1,4 of a branch and forms new alpha-1,4. then, alpha-1,6 of remaining single glucose is broken to release free glucose.

28
Q

under what physiological conditions should the body carry out gluconeogenesis?

A

When the individual has been fasting for over 12 hours. Hepatic (and renal) cells must have sufficient energy for this process, which requires sufficient fat stores for beta-oxidation.

29
Q

what are the enzymes of gluconeogenesis that replace glycolytic enzymes, and which?

A
  1. Pyruvate carboxylase and PEP carboxykinase replace pyruvate kinase
  2. fructose 1,6-bisphosphatase replaces PFK-1
  3. glucose 6-phosphatase replaces hexokinase
30
Q

How does acetyl-CoA shift the metabolism of pyruvate?

A

inhibit PDC. activate pyruvate carboxylase. shift from burning pyruvate in TCA to making glucose. acetyl-CoA for this purpose comes mainly from beta-ox, not glycol.

31
Q

what are the two major metabolic products of the pentose phosphate pathway?

A

ribulose-5-phosphate and NADPH

32
Q

what are the functions of NADPH

A
  1. lipid biosynthesis
  2. bactericidal bleach formation in some white blood cells
  3. maintenance of glutathione stores to protect against reactive oxygen species

Dragon (23 decks)

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