Download Energy Releasing Pathway

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 von Leibig 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 outlined the 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 Pathways
Figure 7.2
1. Glycolysis
a. Where located?
Figure 4.7
Figure 4.8
b. Steps
i. Investment
Three
components:
ii. Splitting
& iii. Harvest
Figure 7.3
i. Investment
Enzyme attaches a P from ATP to glucose after diffusing into the
cell. Prevents glucose from diffusing back out of cell.
Attach another P from second ATP to glucose
Generates a balanced molecule with a Pi at either end.
ii. Splitting
Enzyme cuts molecule into two G3P’s.
Liberates H+ and NAD+ steals the electrons from H+ to form NADH +
H +.
The hole left by the leaving H+ is backfilled by Pi.
This step balances the G3P with a P on either end.
This happens twice or once for each G3P.
How many NADH + H+ are formed per glucose?
iii. Harvest
Enzyme directly transfers a P from G3P to ADP to make ATP.
How many times does this happen to make how many ATP’s?
Makes two molecules of pyruvate.
Figure 7.4
Substrate-level phosphorylation (SLP)
or Direct Phosphorylation (ATP synthesis)
c. Outcomes
i. The ATP’s are used by the cell.
The next two outcomes only happen if
oxygen is present in the cell.
ii. The NADH + H+ transported to the mitochondria and
used in the electron transport chain.
iii. The 2pyruvic acids are each combined to Co enzyme A
(CoA) to go to the mitochondria and the Kreb’s cycle.
2. Transport to Mitochondria
a. Where located?
Figure 7.5
b. Steps
Taxi anyone?
i. Splitting
ii. Adding
Figure 7.6
i. Splitting = Enzyme splits off a CO2 from a pyruvate which
liberates electrons from Hydrogen and given to NAD+ to form
NADH + H+ to make a 2C acetyl group (acetic acid).
ii. Adding = Combine the acetyl group to Co-A to be transported
to the mitochondria.
c. Outcomes
i. The NADH + H+ transported to the mitochondria and
used in the electron transport chain.
The next three outcomes only happen if oxygen
is present in the cell.
ii. The 2pyruvic acids are each combined to Co enzyme A
(CoA) to go to the mitochondria and the Kreb’s cycle.
iii. CO2 diffuses into cytosol and lost.
3. Kreb’s Cycle
a. Where located?
Six step Kreb’s cycle  mitochondrial matrix
Figure 7.6
b. Steps
An enzyme adds acetic acid to oxaloacetic acid to make
citric acid. The cycle is divided into the destroying and
rearranging side.
Acetic acid
Oxaloacetic acid
Citric acid
Figure 7.6
i. Destroying
Enzyme combines acetic group with oxaloacetic acid to begin cycle.
Enzyme splits out CO2 and liberates H+ to NAD+ to make NADH + H+
How many CO2 are liberated per acetic acid? Per glucose?
As H+’s are removed then a P jumps on only to be removed to
form ATP.
ii. Rearranging
Enzymes reshapes molecule to liberate more H+’s to rebuild
oxaloacetic acid.
Liberates H+ and NAD+ or FAD+ steals the electrons to make
NADH + H+ or FADH2.
This happens twice or once for each acetic group.
c. Outcomes
iii. The NADH + H+ and FADH2 transported to the
mitochondria and used in the electron transport chain.
i. The ATP’s are used by the cell.
ii. CO2 diffuses into cytosol and lost as
waste.
4. Electron Transport Chain
a. Where located?
Inner Mitochondrial Membrane (Imm.)
b. Steps  Divided into build-up and Harvest
Figure 7.9
i. Build Up
NADH + H+ and FADH2 drop the electrons from H+ to a series of
re-dox proteins called cytochromes.
As electrons move down the chain they lose energy which is
used to move the H+ proton across the Imm. to establish potential
energy.
ii. Harvest
The electrons are eventually passed to an awaiting Oxygen atom.
The H+ proton moves back across the Imm. through ATP
synthase and to the waiting O2 to form water.
Conversion of energy (Potential to Kinetic) is used to form
ATP.
c. Outcomes
iii. Water moved out or used.
ii. NAD+ and FAD+ sent back to be reused.
i. ATP used by the cell.
5. Summary of Aerobic Respiration
Figure 7.8
C. Anaerobic Respiration
1. Fermentation
Fermentation uses only glycolysis for ATP
production.
Which kingdoms perform this strategy ?
2. Lactic Acid Shuttle
Animal cells use lactic acid shuttle and
Liver
D. Versatility
1. Pathways
2. Problems & Issues
What does this
picture explain
about your diet?
Figure 7.11