Unit I Glycolysis Flashcards
What does glycolysis mean?
carbohydrate breakdown
Is glycolysis anerobic or aerobic?
anerobic
How many pyruvates are produced from 1 glucose molecule?
2
Besides pyruvate, what other key products are made from glycolysis?
ATP and NADH
What is fast glycolysis?
pyruvate is converted to lactic acid and alanine
What is slow glycolysis?
pyruvate is sent to mitochondria and used in aerobic metabolism instead
Glycolysis yields precursors for which aerobic systems?
Krebs and ETS
Where in the cell does glycolysis take place?
the cytosol
To enter krebs, the product pyruvate from glycolysis, must first become what?
first it’s sent to the mitochondria and then converted to acetyl-CoA
What is the fate of glucose in glycolysis?
to become ATP or a precursor for aerobic metabolism
What is the prep step in glycolysis?
phophorylation glucose
Phosphorylating glucose does what?
it traps it in the cell so it cant get out
The product of phosphorylating glucose is what?
glucose-6-phosphate
What is the enzyme that helps produce G-6-P?
hexokinase
What is coupled with hexokinase in the making of G-6-P?
ATP
Is the reaction of glucose to G-6-P endergonic or exergonic?
endergonic
Is glucose to G-6-P reversible or irreversible?
irreversible
G-6-P to fructose-6-phosphate is catalyzed by which enzyme?
phosphoglucose isomerase
is G-6-P to F-6-P irreversible?
yes
F-6-P to Fructose-1,6-bisphosphate is catalyzed by which enzyme?
phosphofructokinase “PFK”
What is PFK coupled with in the phosphorylation of F-6-P?
ATP
Is the phosphorylation of F-6-P a key rate limiting step?
yes
What are the rate limiting steps of the first half of glycolysis?
glucose to G-6-P and F-6-P to F-1,6-BP
What is the purpose of glycolysis?
to make ATP, pyruvate, and precursors for aerobic metabolism
What are the two products of splitting F-1,6-BP?
Dihydroxyacetone phosphate and Glyceraldehyde-3-Phosphate
What catalyzes the reaction of F-1,6-BP to DHAP and G-3-P?
aldolase
Is F-1,6-BP to DHAP and G-3-P a reversible reaction?
yes
DHAP gets converted to what in glycolysis?
G-3-P
what reacts with DHAP to make G3P?
triose phosphate isomerase
Is the isomerization of DHAP a reversible reaction?
yes
How many pyruvates does glycolysis make again?
2
In the redox reaction of G-3-P what is the product?
1,3-bisphosphoglycerate
What is the enzyme in the redox reaction of G-3-P?
G3P-dehydrogenase
What catalyzes the reaction of 1,3-BPG to 3-PG
phosphoglycerate kinase
What is 3-PG converted to in glycolysis?
2-phosphoglycerate
What catalyzes the reaction of 3-PG to 2-PG?
phosphoglycerate mutase
2-PG is catalyzed to phosphoenolpyruvate by what enzyme?
enolase
Is the dehydration of 2-PG a reversible reaction?
yes
PPE is catalyzed to pyruvate by what enzyme?
pyruvate kinase
What is the third and final irreversible reaction in glycolysis?
PPE to pyruvate
How many ATP are yielded in glycolysis?
two
List the key regulatory enzymes of glycolysis
hexokinase, PFK, and Pyruvate kinase
Is hexokinase an isozyme?
yes
What is an isozyme?
different version of the enzyme
Hexokinase I-III is for
energy production
Hexokinase IV is for
blood glucose homeostasis
What is another name for hexokinase IV?
glucokinase
Which type(s) of hexokinase have a high affinity for glucose? (low Km)
Hexokinase I-III
Hexokinase I-III is inhibited by what?
by its product G-6-P
Where is glucokinase located?
in the liver and beta cells of the pancreas
Does glucokinase have a high or? low affinity for glucose?
low affinity but a high Km
What is the purpose of glucokinase having a lower affinity?
so that the brain and muscle can capture glucose more easily
Is glucokinase inhibited by its product?
no it is not
What is glucokinase stimulated by in the liver?
insulin and fructose
What is hexokinase stimulated by in the muscle?
glucose
When an excess of glucose is present in the liver what does glucokinase do?
increases uptake and converts it to fat and glycogen
Inhibition of PFK would also cause the inhibition of?
hexokinase
What is the rate limiting step of glycolysis?
PFK (F6P to F-1,6-BP)
When ATP binds to PFK, what does it do?
ATP will decrease PFK’s activity
Would a high energy charge inhibit or stimulate PFK?
It would inhibit
What would have to happen to pH to inhibit PFK?
it would have to significantly decrease
An intermediate of Krebs that also inhibits PFK
citrate
What is an allosteric enzyme?
an enzyme with many active sites
Would waste or end products inhibit or stimulate glycolysis?
inhibit
What alternate pathways can G6P be used in?
glycogen synthesis or pentose phosphate pathway
Describe PFK-1
catalyzes formation of F-1,6-BP and is used in glycolysis
Describe PFK-2
catalyzes formation of F-2,6-BP in a different pathway
What is the most potent activator of PFK-1?
F-2,6-BP
What would yield F-2,6-BP?
the phosphorylation of F6P by PFK-2
What stimulates PFK-2?
insulin
What does PFK-2 stimulate?
glycolysis and PFK in the liver
What does PFK-2 inhibit?
gluconeogenesis
What decreases F-2,6-BP?
glucagon
What is the enzyme of the third irreversible step in glycolysis?
pyruvate kinase
what is pyruvate kinase inhibited by?
alanine or ATP
What would stimulate pyruvate kinase (PK)?
F-1,6-BP
In the liver, phosphorylation of PK would?
inactivate liver PK
In the liver, what reactivates PK?
dephosphorylation
PFK is linked to PK through a?
feedforward link
What are the fates of pyruvate from glycolysis?
alanine, lactate,and aerobic metabolism
What must happen to pyruvate to become alanine?
It must gain an amine group
What converts pyruvate to lactate?
lactate dehydrogenase
What is lactate dehydrogenase coupled with in the conversion of pyruvate to lactate?
NADH
What happens when pyruvate accumulates in an exercising muscle?
it is converted to lactate
What does the presence of lactate do to glycolysis?
It speeds it up
The increase of NAD from the production of lactate would stimulate or inhibit G3P dehydrogenase?
stimulate
A large amount of lactate would stimulate or inhibit glycolysis?
inhibit
A significant drop in pH inhibits or stimulates PFK?
inhibits
Where is fructose phosphorylated to be used in glycolysis?
in the muscle and kidney
When fructose is phosphorylated in the muscle and kidney what is produced?
F6P
What phosphorylates frucotse to F6P in the muscle and kidney?
hexokinase
What is coupled with hexokinase to convert Fructose to F6P in the muscle and kidney?
ATP
When would fructose be used in glycolysis over glucose when in the muscle and kidney?
when there is a large amount of frutcose
Why is glucose used before fructose?
because of hexokinase’s affinity for glucose
In the liver, what converts fructose to F1P?
fructokinase
What is coupled with fructokinase in the conversion of fructose to F1P?
ATP
In the liver, what converts F1P to Glyceraldehyde and DHAP?
F-1P-aldolase
In the liver, what converts glyceraldehyde to G3P?
triose kinase
In the liver, what converts DHAP to G3P?
triose phosphate isomerase
In the liver, what is the key entry point into glycolysis?
G3P
For galactose entry into glycolysis, what is most important?
that it be converted into G6P
