Glycolysis Flashcards
Where does glycolysis take place
the cytosol
where does the citric acid cycle occur
in the mitochondria
where does the pentose phosphate pathway occur
in the cytosol
where does most of gluconeogeneis occur
in the cytosol
what does the glut transporter relie on ?
The glut transporter requires facilitated diffusion.
what kind of transport is the the glut transporter?
This is an example of secondary active transport because it is going against the concentration gradient.
how does glucose enter the cell?
Before we can even break glucose down, we have to find a way to even bring it into the cell first. It uses a transporter that brings it into the cell, this transporter is called GLUT 1
is insulin signaled during starvation or well fed?
well fed
describe the role of insulin
insulin is a hormone that is signaled during a well fed state, it increases glucose transporters on cell, the overall goal is to get sugar out of the blood stream and store it.
where are enzymes for glycolysis found?
Enzymes of glycolysis are located in the cytosol, where they are only loosely associated, if at all, with each other or with other cell structures.
Glycolysis converts glucose to __ C3 units
Glycolysis converts glucose to two C3 units
how many reactions are in glycolysis
10
in which reactions is ATP invested?
in reactions 1 and 3
in which reactions of glycolysis is ATP generated
7 and 10
NAD can be thought of as an ___ shuttle
electron shuttle.
Write the overall reaction of glycolysis
Glucose + 2NAD+ + 2 ADP + 2 Pi ➔ 2 pyruvate + 2 NADH + 2 ATP + 2 H20 + 4 H+
Which steps of glycolysis are not reversible?
1,3,10
describe step 1 of glycolysis
Reaction 1 of glycolysis is the transfer of a phosphoryl group from ATP to glucose to form glucose-6-phosphate (G6P) in a reaction catalyzed by hexokinase.
what is the enzyme used in step one of glycoysis
Hexokinase
what 3 sugars can hexose work on
glucose, D-mannose, and D-fructose.
what is the name of the enzyme that is found in the liver but works similar to hekokinase ?
glucokinase,
does hexokinase undergo confirmational changes?
yes
Explain how the confirmational change in hexokinase works
The two lobes that form its active site cleft swing together by up to 8 Å so as to engulf the glucose in a manner that suggests the closing of jaws.
This movement places the ATP close to the —C6H2OH
what role does the exclusion of water play in hexokinase ?
Active site polarity is reduced by exclusion of water, thereby expediting the nucleophilic reaction process
What is the second substrate that is necessary for hexokinase ?
Mg2+–ATP complex
What is the role of Mg2+ in hexokinase?
Mg2+ shields the negative charges of the ATP’s α- and β- or β- and γ-phosphate oxygen atoms, making the γ-phosphorus atom more accessible for nucleophilic attack by the C6-OH group of glucose
explain what an isomerase can do
it can change an aldose to a ketose
what is the name of the second enzyme used in glycolysis
phosphoglucose isomerase (PGI)
reaction 2 of glycolysis is a an isomerization of an ____ to a _____
Isomerization of an aldose to a ketose
in words explain reaction 2 of glycolysis
Reaction 2 of glycolysis is the conversion of G6P to fructose-6-phosphate (F6P) by phosphoglucose isomerase (PGI)
explain the difference between disphosphate and biphosphate
The product is a bisphosphate rather than a diphosphate because its two phosphate groups are not attached directly to each other.
what step is One of the pathway’s rate-determining reactions.
reaction 3
T/F AMP is an allosteric effector of PFK
True, Activity of PFK is enhanced allosterically by several substances, including AMP
list 2 things that Inhibit PFK allosterically
Inhibited allosterically by several other substances, including ATP and citrate.
reaction _#__ is an aldol cleavage (retro aldol condensation)
Reaction 4 is an aldol cleavage (retro aldol condensation)
Does GAP or DHAP continue along glycolytic pathway?
Only one of the products of the aldol cleavage reaction, GAP, continues along the glycolytic pathway
what is the relation between DHAP and GAP
DHAP and GAP are ketose–aldose isomers (like F6P and G6P).
What is the name of the enzyme in last part of the investment phase
Triose phosphate isomerase (TIM) catalyzes this process in Reaction 5 of glycolysis, the final reaction of Stage I
what is the name of the intermediate between DHAP and GAP
Enediol intermediate
what is the name of the enzyme that first contained alpha beta barrels?
TIM was the first protein found to contain an α/β barrel (also known as a TIM barrel),
what is a very significant thing about the enzyme tim ?
TIM has achieved catalytic perfection
rate of the bimolecular reaction between enzyme and substrate is diffusion controlled, so product formation occurs as rapidly as enzyme and substrate can collide in solution
how many molecules of GAP do we have at the end of the first stage of glycolysis?
2
How many ATP are consumed after the end of the investment phase of glycolysis ?
2
name the enzyme in step 6
glyceraldehyde-3-phosphate dehydrogenase (GAPDH)
Describe step 6 in words
Reaction 6 of glycolysis is the oxidation and phosphorylation of GAP by NAD+ and Pi as catalyzed by glyceraldehyde-3-phosphate dehydrogenase (GAPDH)
What is the driving force for reaction 6
Aldehyde oxidation, an exergonic reaction, drives the synthesis of the “high-energy” acyl phosphate 1, 3-bisphosphoglycerate (1,3-BPG)
name the enzyme in reaction 7
phosphoglycerate kinase (PGK).
PGK is ____ in appearance
PGK is bilobal in appearance
How many domains are found on the phosphoglycerate kinse binding site?
2, Mg2+–ADP-binding site is located on one domain, ~10 Å from the 1,3-BPG-binding site, which is on the other domain.
The appearance of PGK is remarkably similar to that of which other enzyme?
The appearance of PGK is remarkably similar to that of hexokinase.
What reactions are coupled in glycolysis ?
GAPDH and PGK Reactions Are Coupled
what is the common intermediate whose consumption in the PGK reaction “pulls” the GAPDH reaction forward
1,3-BPG is the common intermediate whose consumption in the PGK reaction “pulls” the GAPDH reaction forward
describe reaction coupling and name a reaction that is coupled
Slightly unfavorable reaction can be coupled to a highly favorable reaction so that both reactions proceed in the forward direction.
GAPDH and PGK Reactions Are Coupled
does an endergonic reaction have a negative or positive delta g
positive
does an exergonic reaction have a negative or positive delta g
negative
what does of substrate-level phosphorylation mean?
This production of ATP, which does not involve O2, is an example of substrate-level phosphorylation
give an example of substrate level phosphorlation in glycolysis
PGK strongly exergonic nature of the transfer of a phosphoryl group from 1,3-BPG to ADP makes the overall synthesis of NADH and ATP from GAP, Pi, NAD+, and ADP favorable.
This production of ATP, which does not involve O2, is an example of substrate-level phosphorylation
what is a mutase?
Mutase catalyzes the transfer of a functional group from one position to another on a molecule
what is the enzyme in reaction 9 ?
Reaction 9 of glycolysis, 2PG is dehydrated to phosphoenolpyruvate (PEP) in a reaction catalyzed by enolase
what would occur to glycolysis if flouride ions were released?
Fluoride ion inhibits glycolysis by blocking enolase activity. In the presence of Pi, F– blocks substrate binding to enolase by forming a bound complex with Mg2+ at the enzyme’s active site
is reaction 10 of glycolysis coupled?
yes. Reaction 10 of glycolysis, its final reaction, pyruvate kinase (PK) couples the free energy of PEP cleavage to the synthesis of ATP during the formation of pyruvate
which 2 cations does reaction 10 require?
both monovalent (K+) and divalent (Mg2+) cations
why is reaction 10 an example of substrate level phosphorylation?
PK reaction is highly exergonic, supplying more than enough free energy to drive ATP synthesis (another example of substrate-level phosphorylation).
what are the 3 products of glycolysis?
ATP, NADH, PYRUVATE
What is the net yield of ATP per glucose
Net yield of 2 ATP per glucose
the 4 ATP produced in the return phase were produced via ___ level _____
Initial investment of 2 ATP per glucose in Stage I and the subsequent generation of 4 ATP by substrate-level phosphorylation
how many NADH are produced in glycolysis?
Glucose is oxidized to the extent that two NAD+ are reduced to two NADH
what does NADH represent?
Represent a source of free energy than can be recovered by their subsequent oxidation.
Why must NADH be reoxidized ?
NADH must be reoxidized by other means in order to keep the glycolytic pathway supplied with NAD+
How many pyruvate molecules produced per glucose?
Two pyruvate molecules produced through the partial oxidation of each glucose are still relatively reduced molecules.
why is pyruvate is metabolized in anarobic metabolism?
In anaerobic metabolism, pyruvate is metabolized to a lesser extent to regenerate NAD+
what cation is essential for kinase activity?
Mg2+ is essential for kinase activity
is G6P an example of a ketone or aldehyde
the aldehyde is g6p
is F6P an example of a ketone or aldehyde
F6P is the ketone
What is the function of step 2 of glycolysis?
we must use isomerase to convert from g6p to f6p in this step so that when aldolase cut this , there are 2 3 carbon chains.
What is an isomerase?
The enzyme is isomerase, because they are 2 isomers . So anytime we see an isomerase we would think that there was some kind of structural change and no atp would be needed.
The enzyme that puts phosphates on things is called a ____
the enzyme that puts phosphates on things is called kinase.
if something has a large delta g is it it reversible or irreversible?
Things that are irreversible are very large, they are + or minus greater than 10.
what is an allosteric effector?
what is an allosteric effector: it is something that interacts or binds with an enzyme not in its active site. It does not directly compete with the active site.
would AMP cause a shift to the left or the right? would ATP cause a shift to the left or the right?
AMP is letter c on the graph - it shows a smaller km - shifts to the left
ATP and citrate would be letter B- it shows a larger km - shifts to the right
what does an isomerase do?
isomerase is the enzyme because we are changing an aldehyde to a ketone. these are isomers of one another, which explains why the enzyme is isomerase.
what does a dehydrogenase do?
dehydrogenases: they do oxidation and reduction reactions. We can look at the NAD is the reaction and tell if it is being oxidized or reduced. in this case the NAD is gaining an H so it is being reduced
what is the first step that we see substrate level phosphorylation?
in step 7. we make an ATP in this step, this is the first instance of this is substrate level phosphorylation. we are making ATP with out oxygen or water.
what is a mutase? And in which step is an enzyme like this used
enzyme moves just the functional group only = mutase enzyme. Like in reaction 8
what are 2 LIMITING FACTORS OF GLYCOLYSIS ?
2 LIMITING FACTORS OF GLYCOLYSIS IS THAT WE DO NOT REGENERATE NAD OR INORGANIC PHOSPHATE
