Energy Releasing Pathways (Cellular

Respiration)I. Introduction

A. History

1. Antoine Lavoisier in the 1700’s can make wine without living organisms

2. Wohler and VonLeibig supported this idea, but Schwann showed juice would not ferment without yeast. 3. In 1860 Pasteur proved ethanol amount proportional to the amount of yeast present

4. In 1897 the Buchner brothers == steps of glycolysis key to fermentation

5. In the early 1900’s Szent-Györgyi designed Citric Acid Cycle, failed to show relationship to fermentation

6. Krebs in 1938 linked glycolysis to citric Acid Cycle via enzyme CoA Kreb’s Cycle

Cellular Respiration or releasing energy from glucose with the use of O2.

Figure 7.1

B. Aerobic Respiration

Overview of Aerobic Respiration

Figure 7.2

1. Glycolysis

a. Where

Glycolysis cytoplasm

b. Steps

Investment

Splitting

& Harvest

Three components:

Figure 7.3

Investment1. Enzyme attaches a P from ATP to glucose after

diffusing into the cellPrevents glucose from diffusing back out of cell

2. Attach another P from second ATP to glucoseGenerates a balanced molecule with a P at either end.

Splitting 1. Enzyme cuts molecule into two G3P’s

2. Liberates H and NAD+ steals the electrons from H to form NADH + H+ 3. The hole left by the leaving H is backfilled by Pi This step balances the G3P with a P

on either endThis happens twice or once for each G3PHow many NADH + H+ are formed per glucose?

Harvest1. Enzyme directly transfers a P from G3P to ADP to make ATPHow many times does this happen to make how

many ATP’s?2. Makes two molecules of pyruvate

Substrate-level ATP synthesis

Figure 7.4

c. Outcomes

1. 2ATP are used by the cell.

2. NADH + H+ mitochondria and electron transport chain

The next two outcomes only happen if oxygen is present in the cell.

3. 2pyruvic acids are combined to CoA to go to the mitochondria and the Kreb’s cycle

2. Transport to Mitochondriaa.

Where

Cytoplasm to Mitochondrial Matrix

Figure 7.5

b. Steps

Taxi anyone?

Figure 7.6

Transport1. Enzyme splits off a CO2 from a pyruvate which

liberates electrons from H and given to NAD+ to form NADH + H+ to make a 2C acetyl group2. Combine acetyl group to Co-enzyme A to be transported to the mitochondria

c. Outcomes

1. NADH + H+ mitochondria and electron transport chain

The next two outcomes only happen if oxygen is present in the cell.

2. 2pyruvate combined to 2CoA go to the mitochondria and the Kreb’s cycle

3. Kreb’s Cyclea.

Where

Six step Kreb’s cycle mitochondrial matrixFigure 4.20

Figure 7.5

b. Steps

Acetic acid added to oxalacetic acid to make citric acid

Figure 7.6

Oxaloacetic acid

Citric acid

Acetic acid

Destroying 1. Enzyme combines acetic group with oxaloacetic

acid to begin cycle2. Enzyme splits out CO2 and liberates H to NAD+ to make NADH + H+ How many CO2 are liberated?

Rearranging1. Enzyme reshapes molecule to liberate more H’s to rebuild oxaloacetic acid

2. Liberates H and NAD+ or FAD+ steals the electrons to make NADH + H+ or FADH2

This happens twice or once for each acetic group

3. As H’s are removed then a Pi jumps on only to be removed to form ATP

c. Outcomes

1. ATP used

2. CO2 diffuses into cytosol and lost

3. NADH + H+ and FADH2 to electron transport chain

4. Electron Transport Chaina.

Where

Inner Mitochondrial Membraneprotein based reactions oxidation/reduction

reactions release energy to make ATP via ATP synthase

Figure 7.7

Inner Mitochondrial Membraneprotein based reactions oxidation/reduction

reactions release energy to make ATP via ATP synthase

Figure 7.7

b. Steps

Figure 7.8

Build Up

1. NADH + H+ and FADH2 drop the electrons from H to a series of re-dox proteins called cytochromes

2. As electrons move down the chain they lose energy which is used to move the H proton across the membrane to establish potential energy

Harvest 1. The electrons are eventually passed to an awaiting

Oxygen atom2. The H proton moves back across the membrane through ATP Synthase and to the waiting O2 to form water 3. Conversion of energy (Potential to Kinetic) is used to form ATP

c. Outcomes

1. ATP used

2. NAD+ and FAD+ sent back

3. Water moved out

Summary of Aerobic Respiration

C. Anaerobic Respiration1.

Fermentation

Fermentation == only glycolysis

2. Lactic Acid Shuttle

Animal cells == lactic acid shuttle and Liver

D. Versatility1.

Pathways

Figure 7.10

2. Problems

Is random effort rewarded?