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A level Biology
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cellular respiration oxidizes sugar and produces ATP in three main stages
– Glycolysis occurs in the cytoplasm
– The Krebs cycle and the electron transport chain occur in the mitochondria
6.8 Overview: Respiration occurs in three main stages
STAGES OF CELLULAR RESPIRATION AND FERMENTATION
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Mitochondrion
CO2 CO2
NADH
ATP
High-energy electrons carried by NADH
NADH
CITRIC ACID CYCLE
GLYCOLYSIS Pyruvate Glucose
and FADH2
Substrate-level phosphorylation
Substrate-level phosphorylation
OXIDATIVE PHOSPHORYLATION
(Electron Transport and Chemiosmosis)
Oxidative phosphorylation
ATP ATP
Cytoplasm Inner mitochondrial membrane
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Remember NADP+/NADPH from Photosynthesis???
• It was a high energy electron carrier!
• In respiration we have NAD+ that carries high energy electrons and a hydrogen ion in the form of NADH
• FAD is also an electron and hydrogen ion carrier and becomes FADH2
• These will become important in the ETC
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
REDOX reactions
• LEO goes GER
• Lose electron- oxidation
• Gain electron- reduction
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
6.6 Overview: Cellular respiration occurs in three main stages
• Stage 1: Glycolysis
– Glycolysis begins respiration by breaking glucose, a six-carbon molecule, into two molecules of a three-carbon compound called pyruvate
– This stage occurs in the cytoplasm
Copyright © 2009 Pearson Education, Inc.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
6.9 Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid
Figure 6.9A
Glucose Pyruvic acid
* Pyruvic acid = Pyruvate
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Summary of Glycolysis
• In
Glucose (6-C)
2 ADP
2 NAD+
• Out
2 pyruvate; 2(3-C)
2 ATP (net)
2 NADH
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Questions
• Where does glycolysis take place?
• Glycolysis energy yield?
• Breaks glucose into TWO ________.
• Animation
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
6.6 Overview: Cellular respiration occurs in three main stages
• Stage 2: The citric acid (Krebs) cycle
– The Krebs cycle breaks down pyruvate into carbon dioxide and supplies the third stage with electrons
– This stage occurs in the mitochondria
Copyright © 2009 Pearson Education, Inc.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle
6.10 Pyruvic acid is chemically groomed for the Krebs cycle
Figure 6.10
Pyruvic acid
CO2
Acetyl CoA (acetyl coenzyme A)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each acetyl group
6.11 The Krebs cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules
Figure 6.11A
Acetyl CoA
KREBS CYCLE
2 CO2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Citric Acid Production
The Krebs Cycle Section 9-2
Mitochondrion
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Citric Acid Production
Figure 9–6 The Krebs Cycle Section 9-2
Mitochondrion
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Summary
• In
Pyruvate -> Acetyl CoA
NAD+
FAD
ADP
• Out
CO2 (as waste)
NADH
FADH2
(LOTS OF ELECTRONS!!)
2 ATP
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Questions
• Where does the Krebs cycle take place?
• How many ATP are produced?
Animation
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
6.6 Overview: Cellular respiration occurs in three main stages
• Stage 3: Oxidative phosphorylation/Electron Transport Chain
– During this stage, electrons are shuttled through the electron transport chain
– As a result, ATP is generated through oxidative phosphorylation associated with chemiosmosis
– This stage occurs in the inner mitochondrion membrane
Copyright © 2009 Pearson Education, Inc.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The electrons from NADH and FADH2 travel down the electron transport chain to oxygen
• Energy released by the electrons is used to pump H+ into the space between the mitochondrial membranes
• In chemiosmosis, the H+ ions diffuse back through the inner membrane through ATP synthase complexes, which capture the energy to make ATP (same as photosynthesis!)
Chemiosmosis powers most ATP production
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
ATP
H+
Intermembrane space
O2
H2O
1 - 2
Inner mitochondrial membrane
H+ NAD+
H+
H+
H+ H+
H+ H+
H+
H+
H+
H+
H+
H+
Mitochondrial matrix
Electron flow
Electron carrier
Protein complex of electron carriers
NADH
FADH2 FAD
ATP synthase
P ADP +
Chemiosmosis
+ 2
OXIDATIVE PHOSPHORYLATION
Electron Transport Chain
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Summary
In
Oxygen
NADH (carrying electrons)
FADH2 (carrying electrons)
Out
H20
NAD+
FAD
LOTS OF ATP!!!!!
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
What’s the take away message???
• Glycolysis breaks down glucose into pyruvate
• Pyruvate is made into acetyl- CoA (releasing CO2)
• Krebs uses up acetyl- CoA and produces 2 ATP, more CO2, and LOTS OF ELECTRONS CARRIED BY NADH AND FADH2!
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules
6.14 Review: Each molecule of glucose yields many molecules of ATP
KREBS CYCLE
Electron shuttle across membranes
Cytoplasmic fluid
GLYCOLYSIS
Glucose 2
Pyruvic acid
2 Acetyl CoA
KREBS CYCLE
ELECTRON TRANSPORT CHAIN
AND CHEMIOSMOSIS
Mitochondrion
by substrate-level phosphorylation
used for shuttling electrons from NADH made in glycolysis
by substrate-level phosphorylation
by chemiosmotic phosphorylation
Maximum per glucose: Figure 6.14
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Mystery of the Toxic Flea Dip….
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
6.11 CONNECTION: Certain poisons interrupt critical events in cellular respiration
• There are three different categories of cellular poisons that affect cellular respiration
– The first category blocks the electron transport chain (for example, rotenone, cyanide, and carbon monoxide)
– The second inhibits ATP synthase (for example, oligomycin)
– Finally, the third makes the membrane leaky to hydrogen ions (for example, dinitrophenol)
Copyright © 2009 Pearson Education, Inc.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
ATP
H+
O2
H2O
1 - 2 H+ NAD+ NADH
FADH2 FAD
P ADP +
Chemiosmosis
+ 2
Electron Transport Chain
H+ H+ H+
H+
Rotenone Cyanide, carbon monoxide
H+
H+
Oligomycin
ATP synthase
DNP
H+
H+
H+
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Rotenone
• Rotenone is a common pesticide
• Rotenone interrupts the electron transport chain
• It prevents NADH from transferring its electrons and therefore prevents the production of ATP
• If NADH cannot transfer its electrons, there will be a substantial decrease of NAD+ molecules