9.3 Glycolysis Pathway Flashcards
what is the primary pathway for ATP production under anaeroboic conditions and in cells lacking mitochondria?
glycolysis
where does glycolysis take place?
in the cytosol
what 4 reactants does glycolysis use?
1 glucose, 2 NAD+, 2 ADP, 2 Pi
what 5 products does glycolysis generate?
2 pyruvates, 2 NADH, 2 H+, 2 ATP, 2 H20
what does the glucose in glycolysis generate?
2 pyuvates
what does the NAD+ in glycolysis generate?
2 NAD+ make 2 NADH and 2 H+
what do the 2 ADP and 2 Pi of glycolysois generate?
2 ATP
give the overall reaction equation of glycolysis
glucose + 2 NAD+ + 2 ADP + 2Pi double arrow (reversibly yield) 2 pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O
what is the overall energy of the glycolysis reaction? what does this mean in terms of the steps
overall is -2,850 kj/mol which is hella energy and since cells are not large enough, energy would be wasted if all done at once, so the reaction is broken down into smaller steps for more efficient energy usage
what are the 2 stages of glycolysis?
stage 1: 5 steps of investing ATP
stage 2: 5 steps of earning ATP
what do kinases do? how are they used in glycolysis?
transfer a phosphate group between ATP and another substrate; used in glycolysis to make or consume ATP
what do isomerases do? how are they used in glycolysis?
change the structure of a substrate while the molecular formula remains the same; used in glycolysis to create isomers
what dp phosphatases do? how are they used in glycolysis?
remove a phosphate group from a substrate without using ATP; used in glycolysis to release Pi
list 6 classes of enzymes involved in glycolysis
- kinases
- isomerase
- phosphatases
- aldolases
- mutases
- enolases
what is consumed in stage 1 of glycolysis?
2 ATP
what does stage 1 of glycolysis create and produce? (2)
- negatively charged molecules that can’t diffuse out of the cell
- produces 2 glyceraldehyde-3-phosphates for stage 2
what are the most important steps of stage 1 of glycolysis and why? (be able to list them out here)
steps 1 and 3 because they are irreversible and consume ATP
what is reaction 1 of glycolysis?
glucose and ATP are converted to glucose-6 phosphate and ADP by either hexokinase (in body cells) or glucokinase (in pancreas and liver cells)
what happens structurally in reaction 1 of glycolysis?
a phosphate group is added to C6 of glucose
list 4 key points of reaction 1 of glycolysis
- it is irreversible because delta G is very negative! (single arrow in rxn)
- 1 ATP is consumed (out of 2 in this stage)
- phosphorylation precents glucose from leaving the cell
- Mg2+ is required for all kinase reactions to shield negative charges
how does glucose-6-phosphate inhibit hexokinase? what does this mean?
G6P binds to hexokinase and inhibits ATP binding by allosteric regulation; means that the 1st step of glycolysis can be regulated by product inhibition feedback
what is reaction 2 of glycolysis?
glucose-6-phosphate is converted to fructose-6-phosphate by phosphpglucose isomerase
what happens structurally during reaction 2 of glycolysis?
the six-membered ring is converted to a 5-membered ring and the carbonyl is moved from C1 to C2
what is a key point about the activation energy of reaction 2 of glycolysis?
it occurs near equilibrium (low activation energy) so it is a concentration-driven reaction
what happens in reaction 3 of glycolysis?
fructose-6-phosphate and ATP are converted to phosphofructokinase-1 (PFK-1) and ADP by fructose-1,6-bisphosphate
what happens structurally in reaction 3 of glycolysis?
the OH is removed from C1 and a phosphate group is added to C1
list 4 key points about reaction 3 of glycolysis
- it is irreversible!! (single arrow!)
- 1 ATP is consumed
- allosterically regulated by energy charge
- rate limiting step for the entire glycolysis pathway!!!
list 3 activators of PFK-1 and a commonality among them
- AMP
- ADP
- fructose-2,6-bisphosphate
(all signal low energy charge within cell, activate to get glycolysis going to get more energy)
list 2 inhibitors of PFK-1
- phosphoenolpyruvate
- ATP
what happens in reaction 4 of glycolysis?
fructose-1,6-bisphosphate is converted to dihydroxyacetone phosphate and glyceradehyde-3-phosphate by aldolase
what happens structurally in reaction 4 of glycolysis?
our 5-membered ring is split open to yield the two products, each with their own phosphate group
list 3 key points about reaction 4 of glycolysis
- low activation energy, occurs near equilibrium, concentration driven
- reverse aldo condensation
- cellular metabolist concentrations favor forward reaction
what happens in reaction 5 of glycolysis?
dihydroxyacetone phosphate is converted to another glyceraldehyde-3-phosphate by triose phosphate isomerse, with an enediol intermediate
list 3 key points about reaction 5 of glycolysis
- the activation energy is low, equilibrium, concentration driven
- both products from reaction 4 enter the pathway
- products of reaction 5 are quickly removed in steps 6 and 7
describe stage 2 of glycolysis
- 2 G3Ps enter
- 4 ATP produced
- 2 NADH produced
- 2 H+ produced
- reaction 10 is irreversible!!
whawhat is the net ATP gain of glycolysis and why?
net gain of 2; although 4 are produced in stage 2, 2 are invested in stage 1
what is important to remember about the reactants and products of stage 2 of glycolysis?
everything happens twice! because 2 G3P enter!!
what happens in reaction 6 of glycolysis?
2 G3P, 2 NAD+,and 2 Pi are converted to 2 1,3-bisphosphoglycerates, 2 NADH, and 2 H+ by glyceraldehyde-3-phosphate dehydrogenase
what happens structurally in reaction 6 of glycolysis
remove an H from G3Ps, use it to reduce NAD+, and add phosphate groups to the G3Ps
list 3 key points of reaction 6 of glycolysis
- 2 NADH produced
- oxidation of C1
- product quickly consumed, reaction is coupled with step 7 so concentration favors the forward reaction
what happens in reaction 7 of glycolysis?
2 1,3-bisphosphoglycerates and 2 ADPs are converted to 2 3-phosphpglycerates and 2 ATPs byy phosphoglycerate kinase
what happens structurally in reaction 7 of glycolysis?
the phosphate groups are removed from the 1,3-bisphosphoglycerates and added to the ADPs to form 2 ATPs
list 3 key points about reaction 7 of glycolysis
- 2 ATP produced
- reaction is coupled with step 6
- intermediate is 2,3-bisphosphoglycerate
describe the side reaction that occurs in reaction 7 of glycolysis erythrocytes
2 1,3-bisphosphoglycerates are converted to 2 2,3-BPGs!!! by bisphosphoglycerate mutase, which as we know decreases binding of O2 and loows RBCs to deliver their O2!!; then is converted to 3-phosphoglycerate in regular reaction 7
what happens in reaction 8 of glycolysis?
2 3-phosphoglycerates are converted to 2 2-phosphoglycerates by phosphoglycerate mutase
what happens structurally in reaction 8 of glycolysis
the phosphate group is shifted from C3 to C2
what happens in reaction 9 of glycolysis?
2 2-phosphoglycerates aare converted to 2 phsophoenolpyruvates (PEPs) and 2 H2Os by enolase
what happens structurally in reaction 9 of glycolysis?
a dehydration reaction occurs to remove 2 H and 1 O for the H2O release
what happens in reaction 10 of glycolysis?
2 PEPs and 2 ADPs are converted to 2 pyruvates and 2 ATPs by pyruvate kinase
what happen structurally in reaction 10 of glycolysis?
the phosphate groups are removed from PEPs and added to ADPs to form ATPs
list 3 key points about reaction 10 of glycolysis
- irreversible!!! single arrow in rxn!!
- 2 ATP produced
- is actually 2 coupled reactions of PEP to enolpyruvate to pyruvate
