cellular respiration
TRANSCRIPT
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Lecture 6b. Cellular Respiration
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For Reporter # 17
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• Living cells
– Require transfusions of energy from outside sources to perform their many tasks
• To keep working
– Cells must regenerate ATP
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• The giant panda
– Obtains energy for its cells by eating plants
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• Energy
– Flows into an ecosystem as sunlight and leaves as heat Light energy
ECOSYSTEM
CO2 + H2O
Photosynthesisin chloroplasts
Cellular respiration
in mitochondria
Organicmolecules
+ O2
ATP
powers most cellular work
Heatenergy
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• Respiration
- exchange of environmental O2 with CO2 from cells
Cellular respiration
– Is the most prevalent and efficient catabolic pathway
– Consumes oxygen and organic molecules such as glucose
– Yields ATP
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Metabolism
1) Anabolism (synthesis): Photosynthesis
2) Catabolism (breaking down): Respiration
• Catabolic pathways yield energy by oxidizing organic fuels
• The breakdown of organic molecules is exergonic (net loss of energy)
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• An overview of cellular respiration
Figure 9.6
Electronscarried
via NADH
GlycolsisGlucos
ePyruvate
ATP
Substrate-levelphosphorylation
Electrons carried via NADH and
FADH2
Citric acid cycle
Oxidativephosphorylation:
electron transport and
chemiosmosis
ATPATP
Substrate-levelphosphorylation
Oxidativephosphorylation
MitochondrionCytosol
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The Stages of Cellular Respiration: A Preview
• Respiration is a cumulative function of three metabolic stages
– Glycolysis
– The citric acid cycle
– Oxidative phosphorylation
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• Glycolysis
– Breaks down glucose into two molecules of pyruvate
– Means “splitting of sugar”
– Breaks down glucose into pyruvate
– Occurs in the cytoplasm of the cell
• The citric acid cycle
– Completes the breakdown of glucose
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• Oxidative phosphorylation
– Way to activate a molecule, an enzyme attaches an inorganic phosphate-group to a molecule
– Is driven by the electron transport chain
– Generates ATP
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For Reporter # 18
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• About 40% of the energy in a glucose molecule
– Is transferred to ATP during cellular respiration, making approximately 38 ATP
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• Cellular respiration
– Relies on oxygen to produce ATP
• In the absence of oxygen
– Cells can still produce ATP through fermentation
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• Glycolysis
Can produce ATP with or without oxygen, in aerobic or anaerobic conditions
Couples with fermentation to produce ATP
Fermentation
–unaerobic pathway of ATP production
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• In alcohol fermentation
– Pyruvate is converted to ethanol in two steps, one of which releases CO2
• During lactic acid fermentation
– Pyruvate is reduced directly to NADH to form lactate as a waste product
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Fermentation and Cellular Respiration Compared
• Both fermentation and cellular respiration
– Use glycolysis to oxidize glucose and other organic fuels to pyruvate
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Sources:
Lectures for Biology 7th Ed. (N. Campbell and J. Reece) by Chris Romero
• Starr, C. 2003. Biology: Concepts and Applications, 5th ed. Brooks/Cole, USA. 799 pp.