Download Stages of Cellular Respiration and Fermentation

Stages of Cellular
Respiration and
Fermentation
There are three that occur
continuously
Question
The break down of glucose is called
1.
A.
B.
C.
D.
Hydrolysis
Cytolysis
Dehydration synthesis
glycolysis
Question
2. The resulting products of glycolysis include
A.
B.
C.
D.
Sugar
ATP
ADP
water
Question
3. NAD and FAD molecules move the following
throughout the cell
A.
B.
C.
D.
Electrons
Hydrogens
Energy
All of the above
Question
4. The organic product of glycolysis is a
molecule containing ___ carbon atoms
called pyruvic acid
A.
B.
C.
D.
One
Two
Three
Four
Question
5. Pyruvic acid is formed in the cells _____.
A.
B.
C.
D.
Matrix
Stroma
Cytoplasm
Membrane
Question
6. After grooming pyruvic acid enters into the
second stage of aerobic cellular respiration
aka ___.
A.
B.
C.
D.
Krebs Cycle
Electron Transport chain
Substrate level phosphorylation
Chemiosmosis
Question
7. The Krebs cycle takes place in the ___of the
mitochondria.
A.
B.
C.
D.
Inter-membrane space
Outer membrane
Inner membrane
Matrix
Question
8. The products of the Krebs cycle include
A.
B.
C.
D.
ATP
NADH and FADH2
CO2
All of the above
Question
9. Chemiosmosis generates more ATP than
glycolysis because of the presence of
A.
B.
C.
D.
The electron transport chain
Oxygen
ATP synthase
All of the above
Question
10. Glycolysis is an ___ process
A.
B.
Aerobic
Anaerobic
Overview

First two (Glycolysis and Krebs) are exergonic





Break down glucose and other organic fuels
Glycolysis occurs in the cytoplasm
 Begins respiration by breaking glucose into 2 molecules
of pyruvic acid
Krebs Cycle occurs in the mitochondria
 Completes breakdown of glucose by decomposing a
pyruvic acid derivative into Carbon Dioxide
The cell makes a small amount of ATP during these
two stages
The main function of these two stages is to provide
electrons to the third stage of respiration
3rd Stage is the Electron
Transport Chain


Obtains electrons from NADH(the reduced
form of NAD), as well as from FADH2 (the
reduced form of FAD)
This process stores energy that ATP
Synthase uses to make most of the cell’s
ATP by chemiosmosis
Overview of Respiration
Glycolysis: Harvesting
Chemical Energy



“splitting of sugar”
Universal energy-harvesting process- all living
cells (an ancient process)
Begins with a single molecule of sugar


Ends with two molecules of pyruvic acid



6-Carbon sugar
Each has 3-Carbon sugar
As the reaction occurs it releases two molecules
of ATP by substrate-level phosphorylation and
reduces two molecules of NAD to NADH
Thus, banking energy in ATP and NADH
Glycolysis Breakdown



Between glucose and the pyruvic acids there are
intermediates.
Each chemical step leads to the next in succession
Starting materials: glucose (fuel), ADP and
inorganic phosphate, and NAD


Along with a little ATP- thus the cell must expend a little
energy to start glycolysis
Plus a few needed enzymes
Glycolysis continued…

2 sets of stages



First is preparatory and consumes energy
 ATP energy(2 molecules) is used to split glucose into
two smaller ones
Second is energy yielding.
 Because there are two pyruvic acids, all of these stages
occur in duplicate.
 NADH is produced along with the oxidation of sugar,
and 4 ATP are produced.
Thus, the net gain of ATP during Glycolysis is 2
ATP per molecule of glucose



Accounts for 5% of the energy that a cell can harvest
from a molecule of glucose
NADH in 2 set of stages account for an additional 16%
of potential ATP
Most organisms need a lot more energy than that!
Glycolysis
Details of Glycolysis
Pyruvic Acids get “groomed”
for the Krebs Cycle

Pyruvic acid diffuses through cytoplasm into the
mitochondria



It is oxidized while NAD+ is reduced to NADH
A carbon atom is removed/released as CO2
Coenzyme A (from B vitamin) joins with the 2-Carbon
molecule remaining to form acetyl coenzyme A (acetyl
CoA)
 Fuel molecule for the Krebs cycle
 For each molecule of glucose that entered glycolysis, two
molecules of acetyl-CoA enter the Krebs Cycle
Preparation for Krebs
Krebs Cycle

Coenzyme A helps the acetyl enter into the Krebs
cycle and then splits and is recycled


Only the 2-C acetyl enters
Each step is catalyzed by a specific enzyme



Disassembles acetyl CoA
Strips its electrons
Casts off 2 Carbons as CO2 per acetyl fragment that
enters into the Krebs cycle
Krebs Cycle Continued…




Each turn of the cycle yields one molecule of
ATP by substrate level phosphorylation
Also yields 3 NADH molecules and one molecule
of FADH2 molecule
Since there are two acetyl CoA molecules per
glucose molecule, the actual yield is: 2ATP, 6
NADH, and 2FADH2
By this point, the cell has gained a total of 4 ATP,
10 NADH and 2 FADH2

To actually use all of this energy, the cell must transfer
all of the energy in the NADH and FADH2 to ATP
Krebs Cycle

.
Chemiosmosis powers most
ATP production



Final stage: ETC and ATP synthesis by
chemiosmosis
With chemiosmosis, the spatial arrangement
of membrane bound proteins makes it
possible for mitochondria to use chemical
energy to create a H+ gradient
Can then use energy stored in the gradient to
drive ATP synthesis
Chemiosmosis in the
Membrane
The how, where, and why


ETC of cellular respiration is in the inner
membranes of the mitochondria.
Cristae (folds of the membrane) extend its
surface area.





Many copies of ETC and many ATP synthase
complexes
Can produce many ATP simultaneously
Pathway of electrons: NADHETC O2
Each oxygen atom combines with 2 electrons
and 2 hydrogens to form H2O ( one of the final
products of cellular respiration)
All carriers bind and release electrons in redox
reactions.
What happens when redox
occurs?




Use energy released from electrons to move H+
across the membrane from the matrix into the inner
membrane space.
The resulting H+ gradient stores potential energy
Poised to produce a LOT of ATP
ATP Synthase provides the channel to allow H+ ions
through


Contains the enzyme necessary to catalyze the
phosphorylation of ADP to ATP
As H+ ions pass through, they drive ATP synthesis
Finally




Via Chemiosmosis, the cell can couple the
exergonic reactions of the ETC to the endergonic
formation of ATP.
The total net yield of ATP per glucose molecule has
a maximum of 38.
This can be interfered with, ie. Certain poisons or
toxins
Without O2, chemiosmosis cannot occur. What
then???
ATP Yield
Poisons that can block the
ETC

Anaerobic alternatives



Some organisms, like yeast and bacteria can
survive without oxygen. They use only the 2
ATP generated from glycolysis
But how can they replenish the NAD+ from its
reduced form
Use Fermentation!
Types of Fermentation

Alcoholic Fermentation



Can convert pyruvic acids to CO2 and ethyl alcohol
Yeasts release alcoholic wastes into the environment, but
die if the alcohol becomes too concentrated
Lactic Acid Fermentation




Produces lactic acid when NADH is oxidized
No CO2 is produced
Used in dairy industry- cheese and yogurt
If you get a “stitch” it can be broken down by liver to end
muscle cramp
Fermentation
Oxygen-lacking conditions

Strict Anaerobes



Require anaerobic conditions
Oxygen is poisonous
Facultative anaerobes (E.coli) can make ATP
by fermentation or chemiosmosis depending
upon conditions
Cells use all kinds of organic food
sources
Also use food for biosynthesis
But where does all of this food
come from?


Photosynthesis
Time to reverse the reaction!