Essay on Chapter 6 Cellular Repiration notes

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Chapter 6: Cellular Respiration

1

DuBoff, B., et al. (2012). Neuron, 75, 618–632

The Key Concepts

Cellular respiration breaks down organic compounds to produce ATP
Transfer of electrons stores energy for chemiosmosis

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What is Bioenergetics?

The application of thermodynamic principles to organisms and biological systems
The fundamental characteristics of all living things is the ability to carry out metabolism
Without metabolic processes life would not exist

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Releasing Chemical Energy

4

Respiration Uses ‘Redox’ Reactions

Carbons of Glucose are oxidized to CO2 a loss of electrons
O2 is reduced to 2 H2O a gain of electrons

5

Respiration Has 4 Parts
Glycolysis
(Breakdown of Glucose)

Cytosol

Breakdown of Pyruvate

Mitochondria Matrix

Krebs Cycle

Mitochondria Matrix

Electron Transport Chain

Mitochondria Inner
Membrane 6

Glycolysis

6 Carbon Glucose is broken down to two 3 Carbon Pyruvate molecules This produces ATP and NADH

7

NADH is simply an electron carrier

It can move electrons from one place in the cell to another

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Investment Phase: ATP is invested to make Glucose more energetic

Investing a little ATP to get a lot later
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Relative Change in Energy (kJ/mol)

Energy Investment

Energy Recovery

ADP + Pi
ATP
ADP + Pi
2 NAD+

ATP

2 NADH + H+

Glu
2 ADP + 2Pi
2 ATP

2 ADP + 2 Pi

2 ATP

2 Pyruvate

By end of Glycolysis the 2 ATP investment is recouped and 2 more ATP are obtained along with 2 molecules of NADH and 2 Pyruvate
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Glycolysis makes ATP by Substrate Level Phosphorylation

A- P P

A- P P P

P

PEP

Pyruvate

Substrate Level Phosphorylation - the production of
ATP by phosphate transfer from substrate to ADP
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We Now Move to the Mitochondrion

Pyruvate Import requires a transport protein
With the break down of
Pyruvate we see the first
CO2 released
More NADH is produced
CoA attaches to the remaining 2 carbons to produce Acetyl-CoA
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Conversion of Pyruvate to Acetyl-CoA

Addition of CoA makes the molecule more reactive like phosphorylating Glucose
Electrons are taken away to produce NADH
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The Citric Acid (Krebs’) Cycle
Nobel Prize in Medicine in 1953 for discovery of the
Citric Acid Cycle
Shared with Fritz Lipmann
(Harvard University) for discovery of Coenzyme A

Sir Hans Krebs
Sheffield University, UK
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The Citric Acid Cycle

The key points: per Acetyl-CoA
2 CO2 is released
3 NADH produced
1 FADH2 produced
1 ATP produced

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A Series of Redox Reactions

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Pyruvate
Oxidation

Glycolysis
Relative Change in Energy (kJ/mol)

ADP + Pi

Citric Acid Cycle

ATP
ADP + Pi
2 NAD+

ATP

Glu

2 NADH + H+
2 ADP + 2 Pi
2 ATP

2 ADP + 2 Pi

2 ATP
2 Pyruvate
2 CoA

2 NAD+
2 NADH + H+

2 NAD+ + 2 ADP + 2 Pi
2 NADH + H+ + 2 ATP
2 FAD + H+

2 FADH2
2 NAD+
2 NADH + H+

Oxaloacetate

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Energy Conversion

1 Glucose

6 ATP (4 in glycolysis and 2 in Citric Acid Cycle)

2 ATP to start glycolysis
10 NADH
2 FADH2
6 CO2
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All of the remaining energy is stored in NADH.
How do we get it out?

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Mitochondrial Electron Transport:
The Weird Part

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Inner membrane
Space
Complex I

Complex III cytochrome b

H+ H+

H+

Complex IV cytochrome c oxidase H+ Cytochrome c

eUQ

UQH2

e4 e-

H+
+
H

H+

H+

NADH

NAD+ + H+

4 H+ + O2
2 H2O

Mitochondrial Matrix

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During electron transport the reactions are exergonic – energy is given off at each step
Part of the energy is saved by actively transporting H+ ions across the inner membrane 22

So What Does the Electron Transport Chain Do?
1. Moves e- from NADH to O2 to make H2O
2. Moves H+ ions from the matrix to the inner membrane space (from low to high concentration)
This has produced a form of potential energy:

23 http://www.youtube.com/watch?v=GnW_NiiK2WE The ATP Synthase

The ATP Synthase uses 3 H+ to make 1 ATP from ADP

The energy comes from the concentration gradient
The potential energy of the concentration gradient is converted to chemical energy of ATP
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Chemiosmotic Theory

The ATPase uses 3 H+ to make 1 ATP from ADP
The…