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Biochem > Week 5 > Flashcards

Week 5 Flashcards

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1
Q

glycolysis takes place in

A

the cytosol of a cell

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2
Q

glycolysis has how many phases?

A

2

  • energy-requiring
  • energy-releasing
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3
Q

describe energy-requiring phase of glycolysis

A
  • uses 2 ATP
  • starting molecule: glucose
  • rearranged and 2 phosphate groups are attached which makes the sugar unstable to split into two phosphate-bearing 3-carbon sugars
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4
Q

what is the modified sugar intermediate in the energy-requiring phase of glycolysis

A

fructose 1,6-bisphosphate

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5
Q

what are the 3-carbon sugars formed when fructose 1,6-bisphosphate splits

A

glyceraldehyde-3-phosphate

DHAP (which is converted into glyceraldehyde-3-phosphate

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6
Q

describe energy-releasing phase of glycolysis

A

3-carbon sugars are converted into pyruvate by a series of rxns in which 2 ATP and one NADH are made. This repeats twice so a total of 4 ATP and 2 NADH are produced

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7
Q

aerobic pathway glycolysis

A

glucose is oxidized to pyruvate and oxidations continues in mitochondria to generate acetyl-CoA

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8
Q

NAD+ and aerobic pathway

A

it is regenerated by transport of reducing equivalents across the mitochondrial membrane with use of glycerolphosphate shuttle and maltate shuttle

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9
Q

anaerobic pathway glycolysis

A

glucose is oxidized to lactate in the presence or absence of oxygen

occurs in RBS, skeletal muscle under anaerobic conditions, impaired activity of pyruvate dehydrogenase complex

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10
Q

NAD+ and anaerobic pathways

A

regenerated by reduction of pyruvate to lactate

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11
Q

conversion of glucose to glucose-6-phosphate uses what enzymes

A

glucokinase or hexokinase

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12
Q

does the conversion of glucose to glucose-6-phosphate use atp?

A

yes

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13
Q

glucokinase and hexokinase are an example of

A

isozymes

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14
Q

isozyme

A

enzymes that different in amino acid sequence but catalyze the same chemical rxn

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15
Q

hexokinase

A
  • low Km for glucose
  • found in tissues other than liver
  • rapidly saturated
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16
Q

glucokinase

A
  • high Km for glucose
  • found in liver or pancreas
  • not rapidly saturated
  • can remove glucose from bloodstream to allow excess glucose to be stored as glycogen
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17
Q

enzyme for the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate

A

phosphofructokinase-1 (PFK1)

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18
Q

phosphofructokinase-2

A

can convert fructose 6-phosphate to phosphofructokinase-2 as a shunt of glycolysis
activated by dephosphorylation

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19
Q

fructose 2,6-bisphosphate

A

will enhance activity of PFK1

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20
Q

fructose 1,6-bisphosphate is a

A

feedforward activator of pyruvate kinase

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21
Q

does conversion of fructose 6-phosphate to fructose 1,6-bisphosphate use atp

A

yes

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22
Q

enzyme for the conversion of phosphoenolpyruvate to pyruvate

A

pyruvate kinase

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23
Q

pyruvate kinase is regulated by

A

feedforward regulation

allosterically activated by fructose 1,6-bisphosphate

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24
Q

pyruvate from glycolysis can

A
  • enter TCA cycle through pyruvate dehydrogenase complex
  • convert to lactate under anaerobic
  • transminate to alanine
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25
hexokinase inhibited by
glucose 6-phosphate
26
glucokinase + reg by
insulin
27
phosphofructokinase-1 + reg by
insulin
28
phosphofructokinase-1 activated by
F 2,6-p | AMP
29
phosphofructokinase-1 inhibited by
atp | citrate
30
pyruvate kinase + reg by
insulin
31
pyruvate kinase - reg by
glucagon mediated phosphorylation
32
pyruvate kinase activated by
F 1,6-P
33
pyruvate kinase inhibited by
atp | alanine
34
pyruvate dehydrogenase complex co-factors
thiamin lipoate FAD
35
regulation of pyruvate dehydrogenase complex in TCA
acetyl coA NADH phosphorylation by pyruvate dehydrogenase kinase (inactivates)
36
Deficiencies in PDC can result in
lactic acidosis
37
aconitase in TCA is inhibited by
fluoroacetate
38
isocitrate dehydrogenase is negatively regulated by what in TCA
NADH
39
isocitrate dehydrogenase is positively regulated by what in TCA
ADP | Ca2+
40
cofactors of alpha-ketoglutarate dehydrogenase in TCA
thiamine lipoate FAD
41
negative regulator of alpha-ketoglutarate dehydrogenase in TCA
NADH
42
positive regulator of alpha-ketoglutarate dehydrogenase in TCA
Ca2+
43
this enzyme is inhibited by arsenite in TCA
alpha-ketoglutarate dehydrogenase
44
this enzyme catalyzes substrate level phosphorylation in TCA
succinate thiokinase
45
this is the only enzyme of the TCA embedded in the mitochondrial membrane
succinate dehydrogenase
46
the net result of glucose oxidation through glycolysis is
2 ATP 2 NADH 2 pyruvate
47
the process of glycolysis stats with
the phosphorylation of glucose by hexokinase or glucose kinase to glucose 6-phosphate
48
in glycolysis, under aerobic conditions, the pyruvate will
enter into mitochondria and be oxidized to acetyl-coA to enter the tca cycle
49
the three irreversible steps are catalyzed by
hexokinase or glucokinase phosphfructokinase 1 pyruvate kinase
50
pyruvate dehydrogenase complex
oxidized the pyruvate produced by glycolysis to acetyl-coA under aerobic conditions
51
an enzyme that is a key transition point between cytosolic metabolism and mitochondrial metabolism
pyruvate dehydrogenase complex
52
PDC requires
as cofactors - thiamin diphosphate - lipoamide - FAD NAD to move the rxn forward
53
PDC is regulated
allosterically | covalent modifications
54
allosteric regulation of PDC
activated by NAD+ and pyruvate inhibited by acetyl-coA and NADH
55
when PDC is phosphorylated
it is inactivated and the production of acetyle-Coa is reduced
56
PDC is phosphorylated by
pyruvated dehydrogenase kinase
57
pyruvate dehydrogenase kinase regulation
most active when acetyl-coA, NADH, ATP are high
58
PDC is dephosphorylated by
phosphatase
59
phosphatase is activatedby
high levels of CA and insulin this therefore means these high levels activate PDC and increase acetyl-coA production
60
A deficiency in which of the following cofactors would result in decreased activity of the pyruvate dehydrogenase complex? a. thiamin b. biotin c. vit C d. folate
thiamin
61
this is responsible for generating over half of the atp from the oxidation of fuels
TCA cycle
62
the substrate for TCA ___ is generated by the oxidation of...
acetyl-coA - fatty acids - glucose - amino acids - ketone bodies
63
each turn of the TCA cycle produces ___ for each acetyl-coA
3 NADH 3 FADH2 2 carbon dioxide 1 GTP
64
key regulatory enzymes TCA
isocitrate dehydrogenase | alpha-ketoglutarate dehydrogenase
65
isocitrate dehydrogenase is activated
by ADP and Ca
66
alpha-ketoglutarate dehydrogenase is activated by
Ca
67
the regulatory enzymes for TCA are sensitive to
the ratio of ATP to ADP and the ratio of NADH to NAD
68
primary inhibitor for the regulatory enzymes of TCA are
NADH
69
a TCA enzyme requires cofactors. what is the enzyme and its cofactors
alpha-ketoglutarate thiamin lipoate FAD
70
oxaloacetate as an intermediate
can be directly transaminated to aspartate and vice versa
71
alpha-ketoglutarate as an intermediate
can be transminated to glutamate and vice versa
72
propionate as an intermediate
a product of odd-chain FA oxidation that can enter TCA as succinyl CoA
73
alanine as intermediate
transaminated to pyruvate through the pyruvate carboxylase reaction
74
compounds taken out of the TCA cycle
- oxaloacetate for gluconeogenesis in the fasted state as reduced form to be reconverted to phosphoenolpyruvate - citrate moved from mitochondria to cytosol to be used for fatty acid synthesis in fed state
75
Alcohol metabolism increases the production of NADH, increasing the ratio of NADH/NAD+ in the cell. How would you expect this to impact the activity of the TCA cycle?
decreased activity of the TCA cycle
76
Pyruvate dehydrogenase kinase catalyzes a reaction that results in...
the phosphorylation and inactivation of E1 subunit of PDC under conditions where acetyl-coA or NADH are elevated
77
A deficiency in thiamine can reduce the activity of the pyruvate dehydrogenase complex. Under these conditions, you would expect to have a higher than normal blood concentration of?
pyruvate - The pyruvate dehydrogenase complex oxidizes pyruvate, therefore if the complex is deficient pyruvate levels would elevate and be converted to lactate through anaerobic metabolism.
78
What is a summary of the TCA cycle
the process completely oxidizes an acetyl group to carbon dioxide
79
TCA produces ___ which is used to...
produce ATP in the ETC
80
What TCA intermediate is required in the cytosol for fatty acid synthesis?
citrate
81
In order for glucose to be retained in the cell, what modification must occur?
phosphorylation
82
the conversion of glucose to glucose 6-phosphate is ___ in all cells except those in the ____. Why?
irrevisible | kidney and liver because they have the enzyme glucose 6-phosphatase to remove the phosphate
83
Pyruvate dehydrogenase complex is highly regulated. The enzyme will be most active when what compound is high?
pyruvate
84
Certain metabolic conditions will reduce flux through the TCA cycle due to an increase in TCA cycle inhibitors. Elevation of what would be an example of a compound that will reduce activity through the TCA?
NADH
85
this enzyme catalyzes net transfer out of the TCA cycle into gluconeogenesis
phosphoenolpyruvate carboxykinase
86
formation of oxaloacetate from pyruvate is catalyzed by
pyruvate carboxylase
87
pyruvate caboyxlase and acetyl-coA
high levels of acetyl-coA activate pyruvate carboxylase and inhibit pyruvate dehydrogenase ensuring adequate oxaloacetate

Biochem (8 decks)

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