24 terms

Glycolysis

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glycolysis
a metabolic process that breaks down glucose into 2 pyruvate molecules and release energy for the body in the form of ATP; occurs in cytosol; catabloic pathway; means "splitting of sugar,"; no CO2 is released
G step 1
Glucose enters the cell and is phosphorylated by the enzyme hexokinase; the charge of the released phosphate group traps the glucose because the membrane is impermeable to ions; makes glucose more chemically reactive; energy payoff ; requires investment of 1 ATP
hexokinase
transfers a phosphate group from an ATP to a sugar in the second step of glycolysis
G step 2
Glucose 6-phosphate is rearranged by phosphoglucoisomerase to convert to its isomer fructose-6-phosphate; energy investment
phosphoglucoisomerase
turns glucose-6-phosphate to fructose-6-phosphate (isomers)
G step 3
phosphofructokinase transfers a phosphate from another ATP in glycolysis. with a phosphate group on each end, the sugar is ready to split; the main regulatory step of glycolysis. PFK is feedback-inhibited by ATP; energy investment; This step commits the carbon skeleton to glycolysis, a catabolic process, as opposed to being used to synthesize glycogen, an anabolic process
phosphofructokinase
an allosteric enzyme that controls the rate of glycolysis
G step 4
uses aldolase to break fructose-1-6-bisphosphate into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate; energy investment
aldolase
this enzyme cuts the 6-carbon sugar into 2 3-carbon sugars; 2 sugars are isomers of each other
G step 5
isomerase converts Glyceraldehyde 3-phosphate to Dihydroxyacetone phosphate and back again until the net result is two molecules of Glyceraldehyde 3-phosphate; energy investment
isomerase
catalyzes the reversible conversion between Glyceraldehyde 3-phosphate to Dihydroxyacetone phosphate
G step 6
Triose Phosphate dehydrogenase creates 3-biphosphoglycerate; occurs twice, to each Glyceraldehyde 3-phosphate molecule; stores some energy in 2 NADH; energy payoff
Triose Phosphate dehydrogenase
enzyme catalyzes two reactions: the sugar is oxidized by the transfer of e's from H+ to NAD+ (very exergonic reaction) and the enzyme uses the energy to attach a phosphate group (from the cytosol) to the oxidized substrate;
3-biphosphoglycerate
product of step 6 that is very high in potential energy
G step 7
the phosphate of the 3-biphosphoglycerate is added to ADP to create 2 ATP in an exergonic reaction; glucose from step 1 is now an carboxyl organic acid; energy payoff
phosphoglycerokinase
the enzyme that takes the phosphate of the 3-biphosphoglycerate is added to ADP to create 2 ATP in an exergonic reaction;
G step 8
relocates the remaining phosphate group that hasnt been taken from the carboxyc acid from the bottom to the middle; energy payoff
phosphoglyceromutase
converts 3-phosphoglycerate to 2-phosphoglycerate (isomers)
G step 9
uses enolase to convert 2-phosphoglycerate to phosphoenolpyruvate, makes the phosphate group still attatched very unstable; energy payoff
enolase
extracts a water molecule and causes a double bond to form in 2-phosphoglycerate creating phosphoenolpyruvate
G step 10
transfers remaining phosphate from phosphoenolpyruvate (PEP) to ADP creating ATP; energy payoff
pyruvate kinase
phosphoenolpyruvate to pyruvate and release 2 atp
energy investment phase
first 5 steps; , the cell actually spends ATP to phosphorylate the fuel molecules. This investment is repaid with dividends
energy payoff phase
steps 6-10; when ATP is produced by substrate-level phosphorylation and NAD+ is reduced to NADH by oxidation of the food; makes up the ATP used in 1-5; The net energy yield from glycolysis, per glucose molecule, is 2 ATP plus 2 NADH
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