Glycolysis Flashcards
What is the principle pathway through which ATP is generated in the body?
glycolysis
Is glycolysis present in every cell type?
Yes
Where in the cell does glycolysis occur?
cytosol
Is glycolysis high in RBCs? Why or why not?
Yes. They don’t have mitochondria so their only source of ATP is glycolysis
What are the two phases of glycolysis?
1) Preparative phase
2) ATP-generating phase
What happens in the preparative phase of glycolysis?
take glucose, consumes 2 ATPs, and generates 2 triose phosphates
What happens in the ATP generating phase of glycolysis?
2 gylcerol triphoshphates (the triose phosphates from the preparative phase) are converted to 2 pyruvates, generating 4 ATP and 2 NADH
What are the NET products of aerobic glycolysis?
2 NADH, 2 ATP, and 2 pyruvates
What is the first regulated step of glycolysis?
Is this step an ATP consuming step?
glucose is phosphoylated into glc-6-p by hexokinase (glucokinase in the liver)
Yes. An ATP is needed
What happens after glc is phosphorylated into glc-6-p?
glc-6-p is converted to fructose-6-p by phosphoglucose isomerase
What happens after glc-6-p becomes fructose-6-p?
fructose-6-p is acted upon (in an ATP dependent fashion) by phosphofructokinase-1 making fructose-1,6- biphosphate
subject to negative feedback inhibition by ATP and citrate
What is the rate limiting enzyme in glycolysis?
phosphofructokinase-1 (PFK-1)
Why is phosphofructokinase-1 the rate limiting enzyme in glycolysis?
It has four allosteric enzymes on its structure (the most of all) that regulate its activity
What happens to fructose-1,6-biphosphate?
it undergoes a cleavage via an aldolase to generate the two triose phosphates, glyceraldhyde-3-phosphate and dihydroxyacetone phosphate (the two end products of the preparatory phase of glycolysis)
NOTE: these two can be interconverted via an isomerase
What are the intermediates of the preparative stage of glycolysis?
1) glucose
2) glc-6-p
3) fructose-6-p
4) fructose-1-,6-biphosphate
5) glyceraldhyde-3-phosphate and dihydroxyacetone phosphate
What is the committed step of glycolysis?
conversion of fructose-6-phosphate to fructose-1,6-biphosphate via phosphofructokinase-1
What is the major difference between hexokinase and glucokinase other than their location?
hexokinase is regulated through a feedback system. So if glucose is made into glc-6-p and not used, it will inhibit further kexokinase action.
Glucokinase will not be feedback inhibited
What is the first step of the ATP generating phase of glycolysis?
a de-hydrognase step
glyceraldeyhde-3-phosphate is converted to a high energy intermediate (1,3- bisphosphoglycerate). This step consumes NAD+ and produces NADH+