How Cells Harvest Chemical Energy

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Chapter 9 How Cells Harvest Chemical Energy
Introduction to Cell Metabolism Glycolysis Aerob
ic Cell Respiration Anaerobic Cell Respiration
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Breathing and Cell Respiration are related
BREATHING
O2
CO2
Lungs
Muscle cells carrying out
CO2
O2
Bloodstream
CELLULAR RESPIRATION
Sugar O2 ? ATP CO2 H2O
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How efficient is cell respiration?
Energy released from glucose banked in ATP
Energy released from glucose (as heat and light)
Gasoline energy converted to movement
100
About 40
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Burning gasolinein an auto engine
Burning glucose in an experiment
Burning glucosein cellular respiration
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Reduction and Oxidation
OILRIG Oxidation is losing electrons Reduction
is gaining electrons
Loss of hydrogen atoms
Energy
Glucose
Gain of hydrogen atoms
Glucose gives off energy and is oxidized
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Reduction and Oxidation OILRIG Gain
or loss of electrons is often in the form of
hydrogen. The hydrogen is then passed to a
coenzyme such as NAD
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Reduction and Oxidation What are some common
co-enzymes? NAD and FAD
NAD 2 H ? NADH H
FAD 2 H ? FADH2
Remember that H 2 electrons and 2H
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Reduction and Oxidation These co-enzymes are
very important for cell respiration because they
transfer high-energy electrons to electron
transport systems (ETS).
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Reduction and Oxidation As the electrons move
from carrier to carrier, energy is released in
small quantities.
Electron transport system (ETS)
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Generation of ATP There are two ways to
generate ATP Chemiosmosis Substrate-Level
Phosphorylation
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Generation of ATP Substrate Level
Phosphorylation
Enzyme
ATP can also be made by transferring phosphate
groups from organic molecules to ADP
Adenosine
substrate
Adenosine
product
Figure 6.7B
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Generation of ATP Substrate Level
Phosphorylation
Enzyme
ATP can also be made by transferring phosphate
groups from organic molecules to ADP
Adenosine
substrate
Adenosine
product
Figure 6.7B
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General Outline
Glucose
Glycolysis
No Oxygen Anaerobic
Oxygen Aerobic
Pyruvic Acid
Transition Reaction
Fermentation
Krebs Cycle
ETS
36 ATP
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Glycolysis Where? The cytosol What? Breaks
down glucose to pyruvic acid
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Steps A fuelmolecule is
energized,using ATP.
Glucose
1
3
Step
Glycolysis
1
Glucose-6-phosphate
2
Fructose-6-phosphate
Energy In 2 ATP
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Fructose-1,6-diphosphate
Step A six-carbonintermediate splits into
two three-carbon intermediates.
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4
Glyceraldehyde-3-phosphate (G3P) (TRIOSE
PHOSPHATE)
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Step A redoxreaction generatesNADH.
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1,3-Diphosphoglycerate(2 molecules)
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Steps ATPand pyruvic acidare produced.
3-Phosphoglycerate(2 molecules)
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Energy Out 4 ATP
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2-Phosphoglycerate(2 molecules)
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2-Phosphoglycerate(2 molecules)
NET 2 ATP
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Pyruvic acid
(2 moleculesper glucose molecule)
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Transition Reaction/Pre-Krebs/Link Reaction
Occurs in the Matrix
Each pyruvic acid molecule is broken down to
form CO2 and a two-carbon acetyl group, which
enters the Krebs cycle. An Oxidative
Decarboxylation Reaction
Pyruvic Acid
Acetyl CoA
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Krebs Cycle Where? In the Mitochondria/
Specifically in the matrix What? Uses Acetyl
Co-A to generate ATP, NADH, FADH2, and CO2.
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Krebs Cycle
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Krebs Cycle
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Electron Transport System
Proteincomplex
Intermembranespace
Electroncarrier
Innermitochondrialmembrane
Electronflow
Mitochondrialmatrix
ELECTRON TRANSPORT CHAIN
ATP SYNTHASE
Figure 6.12
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Electron Transport System
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CHEMIOSMOSIS

• The coupling of ATP synthesis to electron
  transport via a concentration gradient.
• It is the MECHANISM for oxidative phosphorylation
  in Aerobic C.R. and Photosynthesis

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Generation of ATP Chemiosmosis
Cells use the energy released by falling
electrons in the ETS to pump H ions across a
membrane Uses the enzyme ATP synthase.
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Generation of ATP Chemiosmosis
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Electron Transport System
For each glucose molecule that enters cellular
respiration, chemiosmosis produces up to 38 ATP
molecules
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Overview of Aerobic Respiration
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General Outline
Glucose
Glycolysis
No Oxygen Anaerobic
Oxygen Aerobic
Pyruvic Acid
Transition Reaction
Fermentation
Krebs Cycle
ETS
36-38 ATP
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Fermentation
Requires NADH generated by glycolysis.
Where do you suppose these reactions take place?
Yeast produce carbon dioxide and ethanol
Muscle cells produce lactic acid
Only a 2 ATP are produced per glucose
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Fermentation