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The Process of Cellular Respiration
Learning Objectives
 Describe what happens during glycolysis.
 Describe what happens during the Krebs cycle.
 Explain how high-energy electrons are used by the
electron transport chain.
 Identify how much ATP cellular respiration generates.
Photosynthesis and Cellular Respiration
Photosynthesis and cellular
respiration can be thought
of as opposite processes.
Why??
What do you think
Goes in and comes out?
Where in the cell do you
Think cellular respiration
takes place?
Cellular Respiration
The chemical summary of cellular respiration is:
Oxygen + Glucose  Carbon Dioxide + Water + Energy
What does the equation look like expressed in symbols?
6O2 + C6H12O6  6CO2 + 6H2O + Energy
Energy Review
• Energy Storing Molecules:
– ATP, NADPH (NAD+), FADH (FAD+), FADH2
• ATP supplies most of the energy that drives
metabolism in living things
• ATP releases energy when converted into ADP
Cellular Respiration Overview
Chapter 9
• Living things get most of the energy they
need from glucose.
– Autotrophs make glucose using
photosynthesis
– Heterotrophs get glucose from food they eat
• Cellular Respiration
– The process that releases energy by
breaking down glucose and other food
molecules in the presence of oxygen.
Figure 9–2
Cellular Respiration: An Overview
Mitochondrion
Electrons carried in NADH
Pyruvic
acid
Glucose
Glycolysis
Krebs
Cycle
Electrons
carried in
NADH and
FADH2
Electron
Transport
Chain
Mitochondrion
Cytoplasm
3 Stages of Cellular Respiration
• Glycolysis
• Krebs cycle
• Electron transport
Main source of energy
produced=
ATP!!!!
Glycolysis
Glyco = Glucose
lysis = Breakdown
• Occurs in the cytoplasm of
the cell
• One molecule of glucose is
converted to two molecules
of
pyruvic acid.
Glycolysis: ATP and NADH Production
Cell must use (invest) 2
ATP
Produces Energy Carrier
Molecules
4 ATP
2 NADH
And
2 Pyruvic acid
The End Result of Glycolysis
4 ATP molecule used for energy
2 NADH molecules Electron carriers to ETC
2 Pyruvic Acid Krebs Cycle
After step 1
• After this step there is a fork in the road
• If oxygen is present….
• If no oxygen….
• Lets explore one option today
The Krebs Cycle
Pyruvic acid is broken down into carbon dioxide in a series of
energy-extracting reactions.
• Aerobic Process =
Only occurs if oxygen is
present!!
• Occurs in the MATRIX
of the mitochondria (the
maze)
The Krebs Cycle
Pyruvic acid from glycolysis is used to make NADH, ATP, and FADH2,
with carbon dioxide as a by-product.
1 ATP
3 NADH
1 FADH2
CO2
The Krebs Cycle: Energy Extraction
For each turn of the cycle, a molecule of ADP is converted to
a molecule of ATP.
The End Result of the Krebs Cycle
1 ATP molecule used for energy
3 NADH molecules Electron carriers to ETC
1 FADH2 molecule Electron carrier
CO2 Byproduct
Electron Transport
Products from the Krebs cycle and glycolysis feed into the last
step of cellular respiration- NADH and FADH2
• Occurs in the folds of the
Inner Membrane of the
Mitochondria
• The electrons are
passed down a chain of
proteins until they reach
the final electron
acceptor…..oxygen!
• So this step is aerobic
(requires oxygen)
Electron Transport
Electron transport chain is composed of a series of electron
carriers located in the inner membrane of the mitochondrion.
Electron Transport
Electron transport uses the high-energy electrons from glycolysis
and the Krebs cycle to synthesize ATP from ADP.
Total ATP from Cellular Respiration
Glycolysis, the Krebs cycle, and the electron transport chain release
about 36 molecules of ATP per molecule of glucose.
2
2
CO2
32
Total ATP?
30 to 42