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26 Cards in this Set
- Front
- Back
enzyme that phosphorylates glucose in most tissues
what is the resulting compound? |
hexokinase
G6P |
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in what organs does glucokinase substitute for hexokinase?
what is the difference between them? |
liver, beta cells of pancreas, intestines
glucokinase has a lower affinity for glucose, so these cells only use glucose when it is in high concentrations in the body |
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what is the most important regulatory enzyme in glycolysis
why? |
phosphofructokinase (PFK-1)
it catalyzes the committed step in glycolysis |
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what do kinases do?
what do phosphatases do? |
phosphorylate
de-phosphorylate |
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enzyme that catalyzes the final step in glycolysis
what is produced? |
pyruvate kinase
pyruvate |
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what is the last step of glycolysis
|
phosphoenolpyruvate (PEP) to pyruvate via pyruvate kinase
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what step of glycolysis produces 4 ATPs per molecule of glucose?
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PEP to pyruvate (the last step)
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what enzymes catalyze the steps of glycolysis that use up 1 ATP each?
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hexokinase/glucokinase and PFK-1
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hexokinase is inhibited by ____
glucokinase is inhibited by ____ |
G6P
F6P |
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allosteric inhibitor of PFK-1
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ATP (with the help of citrate)
|
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potent activator of PFK-1
how is this activator formed |
fructose 2,6-bisphosphate
it is formed from F6P via PFK-2 |
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effect of glucagon on glycolysis
when does this occur? |
via cAMP-dependent protein kinase, triggers phosphorylation of PKF-2, which reduces the enzyme's activity
this occurs when blood glucose is low |
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the common pathway for the metabolism of all fuels
|
citric acid cycle
|
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purposes of the citric acid cycle
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to produce substrates for the electron transport chain as well as precursors for various biosynthetic pathways
|
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4 key enzymes in the regulation of the citric acid cycle
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pyruvate dehydrogenase
citrate synthase isocitrate dehydrogenase alpha-ketoglutarate dehydrogenase |
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the activity of the citric acid cycle depends on the availability of ___ for several of the dehydrogenases
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NAD+
|
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the amount of NAD+ available for the citric acid cycle is related to ____
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the rate of NADH consumption in the process of oxidative phosphorylation
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what enzyme is responsible for creating acetyl CoA
|
pyruvate dehydrogenase
|
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what 4 groups of molecules allosterically inhibit PDH
what other enzyme do they activate, and what is it's function? |
NADH, acetyl CoA, ATP, and fatty acids
they stimulate PDH kinase, which phosphorylates PDH, reducing its activity |
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electrolyte that activates PDH phosphatase in muscle
what is it's effect? |
Ca++
restores the activity of PDH, stimulating the citric acid cycle |
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molecules that that activate PDH phosphatase (4)
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Ca2+, AMP, CoA, and NAD+
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effect that insulin has on the citric acid cycle
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stimulates PDH via activation of PDH phosphatase (when glucose is abundant)
|
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citrate synthase activity is limited by the availability of ___ and ___
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oxaloacetate and acetyl CoA
|
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two enzymes of the citric acid cycle that are inhibited by NADH
in muscle, however, ___ activates these enzymes |
isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase
Ca++ |
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two enzymes of the citric acid cycle that are inhibited by ATP
|
citrate synthase and isocitrate dehydrogenase
|
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what form of pyruvate kinase is the active one?
when is this form more prominent? |
dephosphorylated pyruvate kinase
more prominent w/ high blood glucose level |