Lesson 11: Glycolysis Flashcards
glycolysis
literally means “the breaking of glucose”
- net exergonic process in cells and under standard conditions
glucogenesis
is the “biochemical reversal” of glycolysis
cellular localization of glycolsis
- glycolysis occurs in the cytoplasm on eukaryotes and prokaryotes
- is anaerobic, independent of O2
STAGE 1
2 ATP investment
reactions 1-4
0 reduced coenzymes
net negative delta G
Reaction 1:
Name of RXN: Hexokinase
RXN:
Glucose + ATP –>. Glucose -6- phosphate + ADP
Enzyme Name: Hexokinase (or gluckokinase)
—- Phosphoryl group is added to C-6—–
- transferase, far from equi, no reversible under cellular conditions, ATP consumed (kinase)
Reaction 2:
Name of RXN: Phosphoglucoseisomerase
RXN: Glucose-6-Phosphate –> Fructose-6-phosphate
Enzyme Name: Phosphoglucoiosomerase
—– 6 membered ring is converted to a 5 membered ring—-
- Isomerase, Near equi, reversible under cellular conditions depending on [G6P] and [F6P]
Reaction 3:
Name of RXN: Phosphofructokinase
RXN:
Fructose -6-P —> Fructose - 1,6 BP
—- (OH to PO4)—-
Enzyme Name: Phosphofructokinase - 1
- transferase, far from equil, not reversible under cellular conditions, kinase, 2nd and last energy inverstiture of glycolysis
!!!!! when a cell wants to turn off glycolysis, it turns it of here!!!!!
Reaction 4:
Name of RXN: Aldolase
RXN:
Fructose-1,6 Biphosphate –>
Glyceraldehyde -3-P and Dihydroxyacetone - P
Enzyme Name: Aldolase
—–ring opened up —–
- near equil undner cellular conditions, hydrolase, [DHAP] and [GAP] quickly pulled away so Q is less than 1
STAGE 2
- total of 4ATP synthesized in stage II via substrate level phosphorylations
- total of 2 NADH + H+ synthesized
- end product is 2 molecules of pyruvate
Reaction 5:
Name of RXN: Triose phosphate isomerase
RXN:
Dihydroxyacetone - Phosphate –> Glyceraldehyde-3-Phosphate
Enzyme Name: Triose phosphate isomerase
- ketose to aldose isomerization, near equil, rxn easily reversible under cellular conditions
!!!!!! at the end of this step, 2 GAP molecules move throguh the rest of glycolysis
Reaction 6:
Name of RXN: Glyceraldehyde 3 phosphate dehydrigenase (GAPDH)
RXN:
Glyceradldehyde-3-phosphate + Pi + NAD+ —> 1,3 Bisphosphoglycerate (1,3 BPG) + NADH + H+
Enzyme:
Glyceraldehyde 3 phosphate
- No ATP consumed Pi is utilized, another phosphoryl trasnfer reaction – NAD+ is a cofactor and first time NADH + H+ produeced, Near rxn
!!!!! lot of potential energy in 1,3 BPG
Reaction 7:
Name of RXN: Phosphoglycerate Kinase
RXN:
1,3 Bisphophoglycerate + ADP –> 3 - Phosphoglycerate + ATP
Enzyme Name:
Phosphoglycerate Kinase
Reaction 8:
Name of RXN: Phophoglycerate Mutase
RXN:
3-Phosphoglycerate –> 2- Phosphoglycerate
Enzyme Name: Phosphoglycerate mutase
Near EQ rxn, mustases function like isomerases except the phosphte that ends up on C-2 is not the same one that came from C-3
Reaction 9:
Name of RXN: Enolase
RXN:
2-phosphoglycerate –> phosphoenolpyruvate + H2O
Enzyme Name: Enolase
- near eq rxn, belongs to a class of enzymes called lyases ( to make or break double bonds through removal of water)
Reaction 10:
Name of RXN: Pyrivate Kinase
RXN: phosphoenolpyruvate + ADP –> pyruvate + ATP
Enzyme Name: pyruvate kinase
- far from eq rxn, transferase, kinase, free energy pf RP hydrolysis is conserved in the synthesis of ATP in our second and last SUBSTRATE LEVEL PHOSPHORYLATION
which reactions are far from eq:
1,3,10
glycolysis summary
- 10 rxns total
- only 1,3 and 10 are far from eq.
- 2 ATP as inputs
- 4 total ATP as output ) for a net of +2 ATP)
- 2 NAD+ as input
- 2NADH + H+ as outputs (these move onto ETC under aerobic conditions)
- 1 glucose yields 2 pyrivate
- catabolic pathway
Homolactic Fermentation
NADH+ +H recycled to form NAD+ (lactae dehydrogenase)
ex: muscle cells
Alcoholic Fermentation
Pyrivate (w/ pyruvate decarboxylase) –> acetaldehyde –> ethanol
