Glycolysis Glycolysis

Glucose
?glycolysis anaerobic respiration
2 Pyruvate ? ? ? 2 Lactate (sent to liver to be converted back to glucose)
Requires mitochondria and O2 ?pyruvate dehydrogenase
acetyl-CoA
?
TCA Cycle
Glycolysis is the metabolic process of converting 1 molecule of glucose to 2 molecules of pyruvate through a
series of 10 enzyme catalyzed reactions. All the steps of glycolysis occur in the cytosol of a cell and do not
require O2.
Note: converting pyruvate to acetyl-CoA and then acetyl-CoA entering the TCA cycle indirectly
requires O2.
Overall Reaction:
Glucose + 2ADP + 2NAD+ + 2Pi ? 2 pyruvate + 2ATP + 2NADH + 2H+ + 2H2O
Glucose Facts:
A) Main fuel source of brain. The brain uses about 120 g of glucose per day.
Only fuel source for red blood cells, cornea, lens (because these cells have no mitochondria).
Kidney, medulla, testes, leukocytes, white muscle fibers use a lot of glucose because these cells have very few
mitochondria.
B) Starch is the storage form of glucose in plants, and glycogen is the storage form of glucose in animals. The
liver and the muscles are the main storage sites for glycogen. We only store enough glycogen to survive on for
about 1 day.
C) The body maintains a constant level of glucose in the blood.
1) Ingest Glucose
2) Glucose passes through cells of intestinal tract and enters portal blood ? bloodstream
3) Pancreas monitors the level of glucose in the bloodstream and produces hormone regulators of blood
glucose levels
? levels too low, produces glucagons which signals the liver to put more glucose into the bloodstream
?levels too high, produces insulin which signals cells to increase uptake of glucose and signals liver to
take in glucose and store it as glycogen
Glycolysis Pathway:
See figure 14-1 for the glycolysis pathway.
Glycolysis occurs in three stages:
Priming stage- 1-3 consisting of a phosphorylation (kinase), an isomerization, and a second phosphorylation
(kinase). The strategy here is to trap the glucose inside the cell and to form a compound that
can be readily cleaved into symmetrical, phosphorylated three-carbon units.
Splitting stage- 4-5 The strategy here is to cleave fructose into two three-carbon units that are readily
interchangeable.
Oxidoreduction-phosphorylate stage-6-10 consisting of a redox reaction (dehydrogenase), two
dephosphorylation reactions, an isomerase (mutase), and a lyase (enolase). In this stage, ATP is harvested when
the three-carbon fragments are oxidized to pyruvate.