Biology 101 Module 7

1. 7-1
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McGraw-Hill Education.
Chapter 7 Energy
for Cells

2. 7.1 Cellular Respiration
In this section, the following objectives will be covered:
– Explain the role of cellular respiration in a cell.
– List the four phases of cellular respiration, and identify the location of
each within a cell.
– Describe the parts and functions of the mitochondria in cellular
respiration.

3. 7-3
Cellular
Respiration
Produces ATP molecules
Essentially the reverse of
photosynthesis
Requires oxygen
and glucose;
produces carbon
dioxide and water
Reason
you
breathe

4. Cellular Respiration

5. 7-5
Cellular Respiration
Involves Redox Reactions
Oxidation = removal of hydrogen atoms
• Hydrogens removed from glucose
• Gives waste product carbon dioxide
Reduction = addition of hydrogen atoms
• Oxygen accepts hydrogens
• Become waste product water

6. 7-6
Glucose
Is Broken
Down in
Steps
– There are 4 phases of complete
glucose breakdown: glycolysis, the
preparatory (prep) reaction, the citric acid
(Krebs) cycle, and the electron transport
chain (ETC)
– Glucose broken down slowly in steps rather
than one sudden release of energy
– Allows energy to be captured and used to
make ATP
– Coenzymes (nonprotein helpers) join with
hydrogen to carry energy from phase to
phase
– NAD+
→ NADH
– FAD+
→ FADH2

7. 7-7
The Four Phases of Complete
Glucose Breakdown

8. 7.2 Outside the Mitochondria: Glycolysis
In this section, the following objective will be covered::
– Summarize how glycolysis partially breaks down glucose, including
initial reactant and products of the reaction.

9. 7-9
Glycolysis
– Takes place in the
cytoplasm
– Glucose (6 carbons)
broken down into two
molecules of pyruvate (3
carbons)
– Divided into:
– Energy-investment steps
– Energy-harvesting steps

10. 7-10
Glycolysis:
Energy-
Investment Step
– 2 ATP transfer
phosphates to glucose
– Activates them for next
steps
– Every reaction needs
some activation energy

11. 7-11
Glycolysis:
Energy
Harvesting
Steps
– Substrate-level ATP
synthesis produces
four ATP
– Net gain of 2 ATP
– 2 NADH made

12. 7-12
Glycolysis Totals
Next step depends on
oxygen availability
• With oxygen, pyruvate
enters mitochondria
• Without oxygen, pyruvate
undergoes reduction
outputs
glucose 2 pyruvate
2 NAD+
4 ADP + 4 P
Inputs
2 ADP
2 NADH
net

13. 7.3 Outside the Mitochondria:
Fermentation
In this section, the following objective will be covered::
– Explain why fermentation pathways are beneficial when oxygen is not
available.

14. 7-14
Fermentation
Fermentation—anaerobic
breakdown of glucose
Generates only two ATP
total in absence of Oxygen
Oxygen is required for the
complete breakdown of glucose in
aerobic respiration

15. 7-15
Glycolysis
Still
Occurs as
Normal

16. 7-16
Fermentation:
Animal Cells
– Pyruvate reduced to lactate
– Brief burst of energy for muscle cells
– Recovery from oxygen deficit
complete when enough oxygen is
present to completely break down
glucose
– Lactate converted back to pyruvate or
glucose

17. 7-17
Fermentation:
Microorganisms
– Bacteria and other microorganisms use
fermentation to produce:
– Lactate and other organic acids
OR
– Alcohol and carbon dioxide
– Yeast (fungus)—carbon dioxide makes
bread rise, ethanol made into wine
and beer

18. The
Anaerobic
Pathways
2 type of Fermentation
reactions based on the type
of organism

19. 7-19
Fermentation
Inputs
2 lactate or
2 alcohol and 2 CO2
2 ADP
glucose
4 ADP + 4 P
Outputs
net

20. The Anaerobic
Pathways
– Glycolysis and Fermentation work
together to recycle NADH so that
the 2 ATP can continue to be
made
– Large organisms can only survive
on this for short periods of time
while many bacteria and
microorganisms only use
anerobic pathways

21. In this section, the following objective will be covered::
– Describe the parts and functions of the mitochondria in cellular
respiration.
– Identify the inputs and outputs of each pathway of aerobic cellular
respiration (prep reaction, citric acid or Krebs cycle, and ETC).
– Explain the role of oxygen in cellular respiration.
7.4 Inside the Mitochondria

22. 7-22
Inside the
Mitochondria
Mitochondrion: location
of aerobic respiration
Cristae: location of the
electron transport chain
Cytoplasm: location of
glycolysis
Matrix: location of the
prep reaction and the
citric acid cycle

23. 7-23
The
Preparatory
Reaction
– Occurs in mitochondrial matrix
– Produces a substrate that enters the
citric acid cycle
– Occurs twice per glucose molecule
– Pyruvate oxidized, CO2 molecule
given off
– NAD+ → NADH
– 2-carbon acetyl group attached to
CoA to give acetyl-CoA

24. 7-24
The Preparatory Reaction
Pyruvate from glycolysis is oxidized to
a 2-carbon acetyl group that is carried
by CoA to the critic acid cycle.

25. 7-25
The
Citric
Acid
Cycle
– Aka The Krebs Cycle
– Occurs in matrix of mitochondria
– Acetyl CoA transfer acetyl group to C4
molecule—produces citric acid (6 carbons)
– CoA returns to preparatory reaction for reuse
– Acetyl group oxidized to carbon dioxide
– NAD+ → NADH and FAD → FADH2
– Substrate-level ATP synthesis produces ATP
– Two cycles for each glucose molecule

26. 7-26
The Citric Acid Cycle
Additional oxidation reactions produce
another NADH and an FADH2 and
regenerate the original 4-carbon
molecule.
The loss of two CO2 results
in a new 4-carbon
molecule.
Each 2-carbon acetyl group
combines with a 4-carbon
molecule to produce citric
acid, a 6-carbon molecule.
ATP is produced by
substrate-level ATP
synthesis.
Twice, oxidation reactions
produce NADH, and CO2 is
released.

27. 7-27
The Electron
Transport
Chain
– Located in cristae of
mitochondria
– Series of carriers pass
electrons from one to the
other
– NADH and FADH2 deliver
electrons then are recycled
to the earlier phases
– Hydrogen atoms
attached consist of e−
and H2
– Carriers accept only e−
not H2

28. 7-28
The Electron
Transport
Chain
– High-energy electrons
enter/low-energy
electrons leave
– As pair of electrons
passed from one carrier
to the next, energy is
released
– Will be captured for ATP
production
– Final electron acceptor
is oxygen—forms water

29. The Electron
Transport Chain

30. 7-30
ATP
Synthase
– ATP synthesis carried out by
ATP synthase in inner
mitochondrial membrane
– Carriers of electron transport
system pass electrons
– Energy used to pump H+
from
matrix into intermembrane
space—creates H+
gradient
– ATP synthase uses energy to
make ATP

31. 7-31
The ETC in the Cristae
– Orange arrow indicates flow of electrons through carriers in ETC
– H+
ions accumulate in intermembrane space and are then used to in the ATP
synthase complex to form ATP

32. In this section, the following objective will be covered::
– Recognize how alternate metabolic pathways allow proteins and fats
to be used for ATP production.
7.5 Metabolic Fate of Food

33. 7-33
Metabolic
Fate of Food
Energy yield from glucose
metabolism:
– Maximum of 38 ATP
made
– Some cells make only 36
ATPs or less
– 36–38 ATP about 40% of
available energy in a
glucose molecule
– Rest is lost as heat

34. 7-34
Alternative
Metabolic Pathways:
Fats and Proteins
– Cells can use other energy
sources such as proteins and fats
– Fatty acids have longer carbon
chains—yields more ATP
– Intermediates can also be used
to make other products
– Extra food made into fat for
storage

35. Chapter 7
Objective Summary
– You should now be able to:
– 1. Explain the role of cellular respiration in a cell.
– 2. List the four phases of cellular respiration, and identify the location of each within a cell.
– 3. Describe the parts and functions of the mitochondria in cellular respiration.
– 4. Summarize how glycolysis partially breaks down glucose, including initial reactant and products
of the reaction.
– 5. Explain why fermentation pathways are beneficial when oxygen is not available.
– 6. Identify the inputs and outputs of each pathway of aerobic cellular respiration (prep reaction,
citric acid or Krebs cycle, and ETC).
– 7. Explain the role of oxygen in cellular respiration.
– 8. Recognize how alternate metabolic pathways allow proteins and fats to be used for ATP
production.