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General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 22• The path that
electrons take on their way down from glucose to oxygen involves many stops
NADH and Electron Transport Chains
Figure 6.6
1/2(from food via NADH)
2 H+ 2 e−Energy forsynthesis
of
Electron transport chain 2 e−
2 H+1 /2
Slide 23• The first stop is an electron acceptor
called NAD+
• The rest of the path consists of an electron transport chain
Slide 24
• Cellular respiration is an example of a metabolic pathway
• All of the reactions involved in cellular respiration can be grouped into three main stages
The Metabolic Pathway of Cellular Respiration
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 25 A Road Map for Cellular RespirationCytosol
Mitochondrion
High-energyelectronscarriedby NADH
High-energyelectrons carriedmainly byNADH
Glycolysis
Glucose2
Pyruvicacid
KrebsCycle Electron
Transport
Figure 6.7
Slide 26
Stage 1: Glycolysis• A molecule of glucose is split into two
molecules of pyruvic acid
Slide 27
• Glycolysis breaks a six-carbon glucose into two three-carbon molecules
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 28
Figure 6.8
Glucose
2 Pyruvic acid
Slide 29 • Glycolysis makes some ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP
Figure 6.9
Enzyme
Slide 30
Stage 2: The Krebs Cycle• The Krebs cycle completes the breakdown
of sugar
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 31 • In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA
Figure 6.10
CoA
1
2
3Pyruvic
acid
Aceticacid
Coenzyme A
Acetyl-CoA(acetyl-coenzyme A)
CO2
Slide 32
• The Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2
Slide 33
Figure 6.11
Input
Acetic acid
ADP
3 NAD+
FAD
KrebsCycle
Output
2 CO21 2
3
4
5
6
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 34
Stage 3: Electron Transport• Electron transport releases the energy your
cells need to make the most of their ATP
Slide 35
• The molecules of electron transport chains are built into the inner membranes of mitochondria
Slide 36
• When the hydrogen ions flow back through the membrane, they release energy
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 37
Figure 6.12
Proteincomplex
Electroncarrier
Innermitochondrialmembrane
Electronflow
Electron transport chain ATP synthase
Slide 38The Versatility of Cellular
Respiration• Cellular respiration can “burn” other kinds of
molecules besides glucose
Slide 39
Figure 6.13
Food
Polysaccharides Fats Proteins
Sugars Glycerol Fatty acids Amino acids
Amino groups
Glycolysis Acetyl-CoA
KrebsCycle Electron
Transport
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 40 Adding Up the ATP from Cellular Respiration
Figure 6.14
Cytosol
Mitochondrion
Glycolysis
Glucose2
Pyruvicacid
2Acetyl-
CoA
KrebsCycle Electron
Transport
bydirectsynthesis
by directsynthesis
byATPsynthase
Maximumper
glucose:
Slide 41 FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY
• Some of your cells can actually work for short periods without oxygen
• Fermentation
Slide 42
• Human muscle cells can make ATP with and without oxygen
Fermentation in Human Muscle Cells
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 43
• Glycolysis is the metabolic pathway that provides ATP during fermentation
Slide 44
Figure 6.15a
2 ADP+ 2
Glycolysis
Glucose2 NAD+
2 Pyruvicacid + 2 H+
2 NAD+
2 Lacticacid
(a) Lactic acid fermentation
Slide 45
• Various types of microorganisms perform fermentation
Fermentation in Microorganisms
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Slide 46
Figure 6.15b
2 ADP+ 2
2 ATPGlycolysis
Glucose2 NAD+
2 Pyruvicacid
2 CO2 released
+ 2 H+
2 NAD+
2 Ethylalcohol
(b) Alcoholic fermentation
Slide 47 • The food industry uses yeast to produce various food products
Figure 6.16
Slide 48
• Ancient bacteria probably used glycolysis to make ATP long before oxygen was present in Earth’s atmosphere
EVOLUTION CONNECTION:LIFE ON AN ANAEROBIC EARTH
– Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy
General Biology 1004 Chapter 6 Lecture Handout, Summer 2005Dr. Frisby
Chapter 6 Study Objectives
1. Explain why we breathe faster when we exercise.2. Explain why an athlete switches from aerobic to anaerobic metabolism during strenuous
exercise.3. Explain why aerobic metabolism is better for an athlete than anaerobic metabolism.4. Describe where photosynthesis occurs, and explain why this process is important to
ecosystems.5. Define and compare autotrophs and heterotrophs, producers and consumers.6. Explain how the processes of photosynthesis and cellular respiration are complementary to
each other.7. Compare the processes of cellular respiration and breathing.8. Write and explain the overall equation for cellular respiration.9. Explain how the processes of oxidation and reduction are used to transfer electrons from
food molecules to NADH, the electron transport chain, and oxygen.10. Compare the reactants, products, and energy yield of the three stages of respiration
(glycolysis, Krebs cycle, and electron transport chain), then indicate where each processoccurs in the cell.
11. Compare the reactants, products, and energy yield of fermentation in human and yeastcells, then indicate where this process occurs in each type of cell.
12. Explain why it is likely that glycolysis is a primitive form of metabolism.