Cellular Respiration and
Fermentation
Chapter 9
Big Idea #1
Chemical Energy and Food
• Organisms get the energy
they need from food!
• How do cells use this
food?
– They don’t just burn food,
they break it down gradually
getting all the nutrients and
energy out
Chemical Energy and Food
• Energy stored in food is
expressed in units of
calories
– The amount of energy
needed to raise 1 gram of
water by 1° Celsius
– 1 gram of glucose
releases 3811 calories of
heat energy when it is
used
Chemical Energy and Food
• The Calorie (big
C) that you see on
food labels is
actually a
kilocalorie, or
1000 calories.
Chemical Energy and Food
• So only plants break down
food right?
–WRONG!
–All living organisms break
down energy sources
–This is called cellular
respiration
Cellular Respiration
• If oxygen is available, energy is
released from food
• Here is a summary:
Oxygen + sugar  carbon dioxide +
water + ENERGY
OR
6O2 + C6H12O6  6CO2 + 6H2O +
ENERGY
Cellular Respiration
• There are 3
stages of cellular
respiration
1. Glycolysis
2. Kreb’s cycle
3. Electron
transport chain
Cellular respiration
• These stages are called
pathways
• Pathways that require
oxygen are aerobic
– Kreb’s cycle
– Electron transport chain
Cellular Respiration
• Pathways that DO NOT
require oxygen are anaerobic
–glycolysis
What is the relationship between
photosynthesis and cellular respiration?
• Photosynthesis
“deposits” the
energy and cellular
respiration
“withdraws” that
energy.
• Photosynthesis removes CO2
from the atmosphere and cellular
respiration puts it back.
• Photosynthesis releases O2 into
the atmosphere and cellular
respiration uses that O2 to release
energy from the food.
9.1 Quiz
1. In what ways are cellular respiration and
photosynthesis considered opposite
processes?
2. The Greek word glukus means “sweet,”
and the Latin word lysis refers to a
process of loosening or decomposing.
Based on this information, write a
definition for the word glycolysis.
Review
• There are 3 stages of
cellular respiration
1. Glycolysis
-
produces only a small
amount of energy.
Most of glucose’s
energy (90%) remains
locked in the chemical
bonds of pyruvic acid
at the end of
glycolysis.
Review
2. Kreb’s cycle
- During the
Krebs cycle, a
little more energy
is generated from
pyruvic acid.
Review
3. Electron transport
chain
- produces the bulk of
the energy in cellular
respiration by using
oxygen, a powerful
electron acceptor.
Review
• Aerobic
processes
require oxygen
to take place
– Kreb’s cycle
– Electron
transport chain
Review
• Anaerobic
processes DO
NOT require
oxygen to take
place
– glycolysis
The Process of Cellular Respiration
• Glycolysis is the first step of
CR
– Means “sugar breaking”
– Involves many steps
transforming glucose
– The end result is 2 molecules of
a 3-carbon molecule called
pyruvic acid and 2 ATP
Fill in your chart:
Glycolysis
Materials
Materials used/consumed produced/made (net total)
2 ATP
2 ATP
1 sugar/glucose (C6H12O6)
2 NADH
2 Pyruvic Acid
http://www.science.smith.edu/departments/
Biology/Bio231/glycolysis.html
• In the presence
of oxygen,
pyruvic acid
produced in
glycolysis moves
into Kreb’s cycle
– Named after
Hans A. Krebs,
British biochemist
• During Kreb’s cycle, pyruvic acid is
broken into carbon dioxide (CO2) in a
series of energy extracting steps
– This happens in the mitochondrial matrix
• 2 ATP
molecules are
produced,
along with
many
electrons and
CO2
molecules
Fill in your chart:
Kreb's Cycle
Materials
Materials
used/consumed
produced/made
2 pyruvic acids (2 cycles)
2 ATP
8 NADH
6 CO2
1 citric acid
Electron Transport Chain
• Electrons come from both glycolysis and
Kreb’s cycle
• The electron transport chain uses the high
energy electrons from glycolysis and
Kreb’s cycle to convert ADP  ATP
Electron Transport Chain:
Step 3
Electron Transport
Hydrogen Ion Movement
Channel
Mitochondrion
Intermembrane
Space
ATP synthase
Inner
Membrane
Matrix
ATP
Production
Electron Transport Chain
• One “cycle” of the electron transport chain
yields 32 molecules of ATP
Electron Transport Chain
Materials
used/consumed
Materials produced/made
NADH
H2O
32 ATP
The Totals
• How much energy does cellular respiration
generate?
– Together, glycolysis, the Krebs cycle,
and the electron transport chain release
about 36 molecules of ATP per molecule
of glucose.
ATP
The Totals
– Glycolysis: 2 ATP
– Kreb’s cycle: 2 ATP
– Electron Transport
Chain: 32 ATP
• Total: 36 molecules
of ATP per 1
molecule of glucose
Fermentation
• What element does cellular
respiration need to proceed?
–Oxygen!
• What happens when no oxygen is
available for cellular respiration?
–Cells proceed into fermentation
Fermentation
• In the absence of oxygen,
fermentation releases energy from
food molcules by producing ATP
• There are 2 types of fermentation:
– Alcoholic fermentation
– Lactic acid fermentation
Fermentation
• Alcoholic fermentation produces ethyl
alcohol and carbon dioxide
– Yeasts and other microorganisms
– Alcoholic beverages and rising bread
Pyruvic acid + NADH  Alcohol + CO2 + NAD+
Fermentation
• Lactic Acid Fermentation converts
pyruvic acid from glycolysis into lactic
acid
– Process used to make cheese, yogurt,
sour cream, pickles, kimchi
– Muscle cells are lactic acid fermenters
Pyruvic acid + NADH Lactic acid + NAD+