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?