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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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