3. • Overview: Life Is Work• Overview: Life Is Work
• Living cells
– Require transfusions of energy from outside
sources to perform their many taskssources to perform their many tasks
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4. • The giant panda• The giant panda
– Obtains energy for its cells by eating plants
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 9.1

5. • Energy• Energy
– Flows into an ecosystem as sunlight and
leaves as heat Light energy
ECOSYSTEMECOSYSTEM
CO + H O
Photosynthesis
in chloroplasts
C ll l
Organic
+ OCO2 + H2O Cellular
respiration
in mitochondria
molecules
+ O2
ATP
powers most cellular work
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Heat
energyFigure 9.2

6. Capacity to do work
Kinetic energy
› energy of motion
› moving objects perform work by imparting motion to› moving objects perform work by imparting motion to
other matter
› Water gushing through dam turn turbines
› Light to power photosynthesis› Light to power photosynthesis
Potential energy
St d› Stored energy
› Based on location or structure
› Energy stored in molecules

7. Totality of an organism’s chemical process
CATABOLIC PATHWAYSCATABOLIC PATHWAYS
Release energy by breaking down complex
molecules to simpler compoundsmolecules to simpler compounds
Cellular respiration
ANABOLIC PATHWAYS
Consume energy to build complicated molecules
f i lfrom simpler ones
Protein synthesis from amino acids

9. ExergonicExergonic
› Proceeds with a net release of energy
› occurs spontaneously
› “Downhill”
Endergonic
› Absorbs free energy from its surrounding
St f› Stores free energy
› Non spontaneous
› “Uphill”› Uphill

10. Transfer of electrons from a LESS
electronegative substance to a MORE
l i b ?electronegative substance?
Downhill reaction or Uphill reaction?

11. Adenosine Triphosphate
Immediate source of energy that powers
cellular work

12. Phosphates bonds
are so fragile
V t bl- Very unstable

13. When ATP is hydrolyzed, it releases free
energyenergy
Th ll l th tThe cell couples the energy to
endergonicendergonic processprocess by transferring a
phosphate group from ATP to somephosphate group from ATP to some
other molecule
PHOSPHORYLATIONPHOSPHORYLATION
Phosphorylated intermediate- morePhosphorylated intermediate more
reactive (less stable)

16. -Aerobic respiration
-FermentationFermentation

20. “The wholesale release of energy from fuel
is difficult to harness efficiently for
i k”constructive work”
Cellular respiration does not oxidize
glucose in one step

21. Three metabolic stages
1. Glycolysisy y
› Cytosol
› Breakdown of glucose into 2 molecules of pyruvate
2. Krebs cycle
› Mitochondrial matrix
› Decomposes pyruvate into CO› Decomposes pyruvate into CO2
3. Electron Transport chain and oxidative
phosphorylationphosphorylation
› Inner membrane of mitochondria

23. Substrate
phosphorylationphosphorylation
› When any enzyme
transfers a
phosphate group
from a substrate to
ADPADP

24. Oxidative phosphorylation
› Electrons are passed from one electron acceptor› Electrons are passed from one electron acceptor
to another
› Energy released at each step is used to make ATP
› Accounts for 90% of ATP generated

25. 1. Energy investment Phasegy
2. Energy payoff phase

26. Glucose enters the cell
DEBIT: 2 ATP molecules
Ready for splitting

27. Downhill reaction
S b t t h h l ti
Water extraction forms double bond
Substrate phosphorylation

29. Aka Citric Acid Cycley

33. •Occurs in the inner
membrane of mitochondria

34. Inc electronegativityInc electronegativity
Final electron
acceptoracceptor

35. ETC makes no ATP directly
How does the mitochondrion couple ETC
and energy release to ATP synthesis?gy y
CHEMIOSMOSIS

36. H+ gradient couples the redox reactions
of ETC to ATP synthesis
PROTON MOTIVE FORCE

37. NADH- 3 pumps= 3 ATPsNADH 3 pumps= 3 ATPs
FADH2 – 2 pumps= 2 ATPs

41. Fermentation enables some cells toFermentation enables some cells to
produce ATP without the use of oxygen
Cellular respiration
› Relies on oxygen to produce ATPyg p
In the absence of oxygenyg
› Cells can still produce ATP through
fermentation

42. GlycolysisGlycolysis
› Can produce ATP with or without oxygen, in
aerobic or anaerobic conditionsaerobic or anaerobic conditions
› Couples with fermentation to produce ATP

43. Fermentation consists ofFermentation consists of
› Glycolysis plus reactions that regenerate NAD+,
which can be reused by glyocolysiswhich can be reused by glyocolysis

44. In alcohol fermentation
› Pyruvate is converted to ethanol in two steps,
one of which releases CO2

45. D i l ti id f t tiDuring lactic acid fermentation
› Pyruvate is reduced directly to NADH to form
lactate as a waste productlactate as a waste product

48. Both fermentation and cellular respiration
› Use glycolysis to oxidize glucose and other
organic fuels to pyruvate

49. Fermentation and cellular respiration
› Differ in their final electron acceptor
Cellular respiration
› Produces more ATP

50. • Pyruvate is a key juncture in catabolism• Pyruvate is a key juncture in catabolism
Glucose
CYTOSOL
Pyruvate
No O2 present O presentNo O2 present
Fermentation
O2 present
Cellular respiration
Ethanol
or
lactate
Acetyl CoA
MITOCHONDRION
CitricCitric
acid
cycle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 9.18

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

53. Comparison of ETC in Photosynthesis and
RespirationRespiration

55. Mitochondria ChloroplastMitochondria
Electrons from food
molecules (oxidation
Chloroplast
Do not need food to
make ATPmolecules (oxidation
of food molecules)
make ATP
light drives theg
electron flow down an
ETC and H+ gradient
formationformation.