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BIOLOGY - CLUTCH
CH.9 - RESPIRATION
CONCEPT: REDOX REACTIONS
Redox reaction – a chemical reaction that involves the transfer of electrons from one atom to another
□ Oxidation – loss of electrons
□ Reduction – gain of electrons
EXAMPLE:
● The combustion of fuels releases energy.
EXAMPLE:
● Electron carrier – molecules capable of accepting electrons, and donating them, as part of electron transport
□ NAD+ – coenzyme that easily transitions between and oxidized and reduced state, and acts as an electron carrier
□ FADH – coenzyme that easily transitions between and oxidized and reduced state, and acts as electron carrier
EXAMPLE:
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CONCEPT: REDOX REACTIONS
Electron transport chain: a series of molecules that transfer electrons through a series of redox reactions
EXAMPLE:
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CONCEPT: CELLULAR RESPIRATION
Cellular respiration is a series of metabolic pathways that converts the energy in nutrients into ATP.
● Aerobic respiration involves oxygen.
EXAMPLE:
● Aerobic respiration can be broken up into 5 steps:
EXAMPLE: Glycolysis à Pyruvate Oxidation à Citric Acid Cycle à Electron Transport Chain à Oxidative Phosphorylation
1. Glycolysis: glucose (6-C) is broken down into 2 pyruvate (3-C)
□ Supplies electron carriers
□ Generates a small amount of ATP via substrate-level phosphorylation
EXAMPLE:
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CONCEPT: CELLULAR RESPIRATION
2. Pyruvate (3-C) is oxidized to acetyl CoA (2-C)
□ Supplies an electron carrier
EXAMPLE:
3. Citric Acid Cycle: acetyl CoA (2-C) combines with oxaloacetate and is fully oxidized
□ Supplies electron carriers
□ Generates an ATP indirectly via substrate-level phosphorylation
EXAMPLE:
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CONCEPT: CELLULAR RESPIRATION
4. Electron Transport Chain: electron carriers deposit electrons to power proton pumps
□ Generates ATP indirectly via electrochemical gradient
EXAMPLE:
5. Oxidative Phosphorylation: protons move down their concentration gradient, powering ATP synthase
□ Generates a large amount of ATP via oxidative phosphorylation
EXAMPLE:
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CONCEPT: GLYCOLYSIS
Glycolysis is a series of 10 biochemical reactions that catabolize glucose.
□ 1 glucose + 2 ATP + 2 NAD+à 2 pyruvate + 4 ATP + 2 NADH
□ Occurs in the cytosol
● Glycolysis has 2 phases:
EXAMPLE: 1.)
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2.)
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CONCEPT: GLYCOLYSIS
● Phosphofructokinase carries out the second phosphorylation, and is a key regulation point.
EXAMPLE:
Glycolysis Accounting
PRACTICE:
Glycolysis
ATP
NADH
FADH2
Start Molecule
End Molecule
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CONCEPT: PYRUVATE OXIDATION
Pyruvate moves from the cytosol to the mitochondrial matrix.
● The pyruvate dehydrogenase complex removes a fully oxidized carbon, and transfers coenzyme A to the molecule.
□ NAD+ is reduced to NADH
EXAMPLE:
● NADH provides negative feedback to pyruvate dehydrogenase.
EXAMPLE:
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CONCEPT: CITRIC ACID CYCLE
The citric acid cycle is a series of reactions that take place in the mitochondrial matrix.
● The citric acid cycle has four phases:
1. Citrate synthesis: acetyl CoA combines with oxaloacetate to form citrate
2. Decarboxylation: series of reactions that reduce 2 NAD+, and result in the loss of 2 CO2
3. Phosphorylation: GTP is synthesized via substrate-level phosphorylation, in some cells it is then used to form ATP
4. Regeneration: final reactions of the cycle that regenerate oxaloacetate, reduce 1 NADH, and reduce 1 FADH2
● Generates 3 NADH, 1 FADH2, and 1 ATP/GTP for each acetyl CoA
EXAMPLE:
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CONCEPT: CITRIC ACID CYCLE
● Citrate synthase synthesizes citrate from acetyl CoA and oxaloacetate.
● Citrate synthase is negatively regulated by ATP.
EXAMPLE:
● The enzymes which catalyze the reactions resulting in the loss of CO2 are negatively regulated NADH.
● ATP negatively regulates the enzyme of the second reaction.
EXAMPLE:
● Phosphofructokinase is regulated by ATP, ADP, and citrate.
EXAMPLE:
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CONCEPT: CITRIC ACID CYCLE
PRACTICE:
Glycolysis Pyruvate Oxidation Citric Acid Cycle
ATP
NADH
FADH2
Start Molecule
End Molecule
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CONCEPT: ELECTRON TRANSPORT CHAIN
The electron transport chain receives electrons from NADH and FADH2, and passes them through a series of electron
donors and acceptors embedded in the inner mitochondrial membrane.
EXAMPLE:
● The electron transport chain is organized as a series of redox reactions between protein complexes I, II, III, and IV.
● Most of the compounds involved are proteins with cofactors and prosthetic groups that specialize in redox reactions.
□ Cytochromes have iron-containing heme prosthetic groups.
EXAMPLE:
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CONCEPT: ELECTRON TRANSPORT CHAIN
● Ubiquinone and cytochrome c act as electron shuttles between the complexes.
□ Ubiquinone is a lipid soluble molecule (quinone) and can travel through the inside of the membrane.
□ Ubiquinone picks up electrons from NADH at complex I, and from FADH2 at complex II.
□ Cytochrome c picks up electrons from complex III and delivers them to the final complex.
EXAMPLE:
● Complexes I, III, and IV act as proton pumps.
□ Complex I pumps H+ from the mitochondrial matrix, into the intermembrane space
□ Complex III pumps H+ from the mitochondrial matrix, into the intermembrane space
□ Complex IV pumps H+, and uses H+ to form water
● Oxygen is the final electron acceptor, forming water.
EXAMPLE:
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CONCEPT: OXIDATIVE PHOSPHORYLATION
The proton pumps create an electrochemical gradient that stores energy.
EXAMPLE:
● ATP synthase uses the proton-motive force from the electrochemical gradient to power ATP synthesis.
□ ATP synthase synthesizes ATP through oxidative phosphorylation.
● Chemiosmosis is the movement of H+ ions across the membrane, with their electrochemical gradient. EXAMPLE:
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CONCEPT: OXIDATIVE PHOSPHORYLATION
ATP Accounting
EXAMPLE:
PRACTICE: Glycolysis Pyruvate
Oxidation Citric Acid
Cycle ETC Oxidative
Phosphorylation
ATP
NADH
FADH2
Start Molecule
End Molecule
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CONCEPT: ANAEROBIC RESPIRATION
Some organisms perform anaerobic respiration, using something other than oxygen as the final electron acceptor.
□ Obligate anaerobes – oxygen is toxic
□ Facultative anaerobes – can perform respiration with or without oxygen
EXAMPLE:
● Sulfur bacteria use sulfate (SO4-) as their final electron acceptor, forming H2S.
● Methanogens use CO2 as their final electron acceptor, forming CH4.
EXAMPLE:
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CONCEPT: FERMENTATION
Fermentation allows glycolysis to continue in the absence of respiration, by regenerating NAD+.
● Alcohol fermentation – pyruvate is converted to ethanol, releasing CO2 and oxidizing NADH
● Lactic acid fermentation – pyruvate is reduced directly by NADH
EXAMPLE:
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CONCEPT: METABOLIC CROSSROADS
Glycolysis and the citric acid cycle are a crossroads for many metabolic pathways.
● Proteins can be deaminated and converted to acetyl CoA, pyruvate, and intermediates of the citric acid cycle.
● Fats can be broken into glycerol and fatty acids.
□ Glycerol can be converted to G3P.
□ Fatty acids can undergo beta-oxidation to become acetyl CoA.
EXAMPLE:
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