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FERMENTATION: ANAEROBIC
HARVESTING OF ENERGY
© 2012 Pearson Education, Inc.
6.13 Fermentation enables cells to produce ATP
without oxygen
 Fermentation is a way of harvesting chemical energy
that does not require oxygen. Fermentation
– takes advantage of glycolysis,
– produces 2 ATP molecules per glucose, and
– oxidizes NADH back to NAD+
 Fermentation allows an anaerobic path for recycling
NADH back to NAD+.
High O2
Mitochondria (TCA and ETC)
Pyruvate
(from glycolysis)
Little O2
© 2012 Pearson Education, Inc.
Cytoplasm (Fermentation)
Lactic Acid Fermentation
 Animals and certain bacteria
can oxidize NADH through
lactic acid fermentation, in
which
2 ADP
2 P
2 ATP
Glycolysis
Glucose
2 NAD
2 NADH
– NADH is oxidized to NAD+ and
– pyruvate is reduced to lactate.
2 Pyruvate
2 NADH
2 NAD
Animation: Fermentation Overview
© 2012 Pearson Education, Inc.
2 Lactate
Alcohol Fermentation
2 ADP
2 P
2 ATP
 In this process Yeasts (singlecelled fungi)
– oxidize NADH back to NAD+
and
– convert pyruvate to CO2 and
ethanol.
2 NAD
Glycolysis
 The baking and winemaking
industries have used alcohol
fermentation for thousands of
years.
Glucose
2 NADH
2 Pyruvate
2 NADH
2 CO2
2 NAD
2 Ethanol
© 2012 Pearson Education, Inc.
6.14 EVOLUTION CONNECTION: Glycolysis
evolved early in the history of life on Earth
 Glycolysis is the universal energy-harvesting
process of life.
 The role of glycolysis in fermentation and
respiration dates back to
– life long before oxygen was present,
– when only prokaryotes inhabited the Earth,
– about 3.5 billion years ago.
© 2012 Pearson Education, Inc.
6.14 EVOLUTION CONNECTION: Glycolysis
evolved early in the history of life on Earth
 The ancient history of glycolysis is supported by its
– occurrence in all the domains of life and
– location within the cell, using pathways that do not
involve any membrane-bounded organelles.
© 2012 Pearson Education, Inc.
CONNECTIONS BETWEEN
METABOLIC PATHWAYS
© 2012 Pearson Education, Inc.
Cellular Respiration Pathways are Intersection
between Catabolic and Anabolic reactions
 Metabolism = sum total of chemical reactions
occurring in an organism
 Catabolism = Chemical reactions that break down
molecules (energy releasing)
– Ex: cellular respiration, hydrolysis of complex
molecules
 Anabolism = Chemical reactions that build up
molecules (energy requiring)
– Ex: photosynthesis, dehydration reactions to build
macromolecules
© 2012 Pearson Education, Inc.
6.15 Cells use many kinds of organic molecules as
fuel for cellular respiration
 Glucose is primary fuel for respiration and fermentation, ATP
can be generated using
– carbohydrates
– fats
– Proteins
 Fats yield more than 2x as much ATP per gram than carbs or
protein
– 1 g carb = 4-5 Cal
– 1 g protein = 4-5 Cal
– 1 g fat = 10 Cal
Figure 2.2C
Catabolic Pathways
Carbohydrates
Sugars
Food
Fats
Proteins
Glycerol Fatty acids
Amino acids
Amino
groups
Glucose
G3P
Pyruvate
Glycolysis
Pyruvate
Oxidation
Acetyl CoA
ATP
Citric
Acid
Cycle
Oxidative
Phosphorylation
Fig. 7.12a
ATP needed
to drive
biosynthesis
Anabolic Pathways
ATP
Food molecules provide raw
materials for biosynthesis
Citric
Acid
Cycle
Pyruvate
Oxidation
Acetyl CoA
Glucose Synthesis
Pyruvate
G3P
Glucose
Amino
groups
Amino acids
Proteins
Fatty acids Glycerol
Fats
Cells, tissues, organisms
Sugars
Carbohydrates
Cells use intermediates
from cellular respiration
for the synthesis of
other organic
molecules.
1
2
4
5
12
Stored
10
Glycolysis
8
9
Pyruvate
Acetyl-CoA
Krebs
cycle
3
Stored
11
6
7