Glycolysis
and
Fermentation
Unit 4: Energize Your
Life
Ch 9-1
Glycolysis
• Glyco = glucose
Lyse = break down
• One molecule of glucose
(C6H12O6) is broken in half
• This produces 2 molecules of
pyruvic acid (a 3-carbon
compound)
Glycolysis
• Glycolysis occurs in the
cytoplasm.
• Glycolysis does NOT require
oxygen. It is anaerobic!!!
• Glycolysis also occurs very
rapidly. It can produce thousands
of ATP molecules in a few
milliseconds.
Glucose to ATP
• Glycolysis is a chemical reaction
that releases energy from glucose.
• The initial energy COST of this
chemical reaction is 2 ATP
molecules.
• 4 molecules of ATP are produced.
• Net gain of 2 ATP!!!
Electron Carriers in Glycolysis
• One of the reactions in glycolysis
removes 4 high-energy electrons
and converts NAD+ into NADH.
• Each NADH carries 2 electrons.
• NADH transfers the energy to the
Electron Transport Chain (ETC).
• Without NAD+, glycolysis can NOT
occur! All of the NAD+ molecules are
needed to transport electrons.
Glycolysis
Glucose
2 Pyruvic acid
To the electron
transport chain
Fermentation
• Fermentation is also anaerobic.
• Fermentation happens after
glycolysis IF the cell does NOT
have Oxygen.
• Fermentation releases energy
from food molecules in the
absence of oxygen.
Fermentation
• There are 2 main types of
fermentation:
–Alcoholic Fermentation
–Lactic Acid Fermentation
• Occur in the cytoplasm
Alcoholic Fermentation
Pyruvic acid + 2NADH 
alcohol + CO2 + 2NAD+
Examples: wine and bread
(the alcohol evaporates when baked)
Lactic Acid Fermentation
Pyruvic acid + 2NADH 
lactic acid + CO2 + 2NAD+
Examples: milk, yogurt, & muscles
Exercise
• Without oxygen, the body is not able
to produce enough ATP.
• When you perform ANAEROBIC
exercise, you are depriving your
muscles of oxygen.
• Your muscles go through LACTIC
ACID FERMENTATION!
• The lactic acid is what makes you
sore!!!
If the cell has oxygen…
• Aerobic—process that occurs in
the presence of oxygen
• Pyruvic Acid goes to the
mitochondria; fermentation does
NOT occur
–Kreb’s Cycle
–Electron Transport Chain
• To be continued…