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Chapter 6How Cells Harvest Chemical Energy
Introduction to Cell Metabolism
Glycolysis
Aerobic Cell Respiration
Anaerobic Cell Respiration
O2 CO2BREATHING
Lungs
CO2 O2Bloodstream
Muscle cells carrying out
CELLULAR RESPIRATION
Sugar + O2 ATP + CO2 + H2O
Breathing and Cell Respiration are related
Glucose Oxygen gas Carbon dioxide
Water Energy
Cellular Respiration uses oxygen and glucose to produce Carbon dioxide, water, and ATP.
Burning glucose in an experiment
Energy released from glucose
(as heat and light)
100%
Energy released from glucose
banked in ATP
“Burning” glucosein cellular respiration
About 40%
Gasoline energy converted to movement
Burning gasolinein an auto engine
25%
How efficient is cell respiration?
Loss of hydrogen atoms
Glucose
Gain of hydrogen atoms
Energy
Reduction and Oxidation
OILRIG
Oxidation is losing electrons
Reduction is gaining electrons
Glucose gives off energy as is is oxidized
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+
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+
Reduction and Oxidation
These co-enzymes are very important for cell respiration because they transfer high-energy electrons to electron transport systems (ETS).
Reduction and Oxidation
As the electrons move from carrier to carrier, energy is released in small quantities.
Electron transport system (ETS)
Generation of ATP
There are two ways to generate ATP
Chemiosmosis
Substrate-Level Phosphorylation
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.
Generation of ATP
Chemiosmosis
ATP can also be made by transferring phosphate groups from organic molecules to ADP
Figure 6.7B
substrate
product
Enzyme
Adenosine
Adenosine
Generation of ATP
Substrate Level Phosphorylation
ATP can also be made by transferring phosphate groups from organic molecules to ADP
Figure 6.7B
substrate
product
Enzyme
Adenosine
Adenosine
Generation of ATP
Substrate Level Phosphorylation
General Outline
Glucose
Pyruvic Acid
Glycolysis
OxygenAerobic
No OxygenAnaerobic
Transition ReactionKrebs CycleETS
36 ATP
Fermentation
Glycolysis
Where? The cytosol
What? Breaks down glucose to pyruvic acid
Glycolysis
Steps – A fuelmolecule is energized,using ATP.
1 3
1
GlucoseStep
2
3
4
Glucose-6-phosphate
Fructose-6-phosphate
Glyceraldehyde-3-phosphate (G3P)
Step A six-carbonintermediate splits into two three-carbon intermediates.
4
Step A redoxreaction generatesNADH.
55
1,3-Diphosphoglyceric acid(2 molecules)
6
Steps – ATPand pyruvic acidare produced.
6 9 3-Phosphoglyceric acid(2 molecules)7
2-Phosphoglyceric acid(2 molecules)8
2-Phosphoglyceric acid(2 molecules)
9
(2 moleculesper glucose molecule)
Pyruvic acid
Fructose-1,6-diphosphateEnergy In: 2 ATP
Energy Out: 4 ATP
NET 2 ATP
General Outline
Glucose
Pyruvic Acid
Glycolysis
OxygenAerobic
No OxygenAnaerobic
Transition ReactionKrebs CycleETS
36 ATP
Fermentation
General Outline of Aerobic Respiration
Glycolysis
Krebs Cycle
Electron Transport System
Transition Reaction
Transition Reaction
Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle
Acetyl CoAPyruvic Acid
General Outline of Aerobic Respiration
Glycolysis
Krebs Cycle
Electron Transport System
Transition Reaction
Krebs Cycle
Where? In the Mitochondria
What? Uses Acetyl Co-A to generate ATP, NADH, FADH2, and CO2.
Krebs Cycle
Krebs Cycle
General Outline of Aerobic Respiration
Glycolysis
Krebs Cycle
Electron Transport System
Electron Transport System
Figure 6.12
Intermembranespace
Innermitochondrialmembrane
Mitochondrialmatrix
Proteincomplex
Electroncarrier
Electronflow
ELECTRON TRANSPORT CHAIN ATP SYNTHASE
Electron Transport System
Electron Transport System
For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules
Overview of Aerobic Respiration
General Outline
Glucose
Pyruvic Acid
Glycolysis
OxygenAerobic
No OxygenAnaerobic
Transition ReactionKrebs CycleETS
36 ATP
Fermentation
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 few ATP are produced per glucose
Fermentation
