Energy conversion: Fermentation
Announcements
-No quiz during next week lab. session
-Write an informal summary about today lab.
I will discus this at the end of the lab.
-Photosynthesis will be taught in 2 lab. session
come prepared (as usual) and for the first week
exercise; read the protocol at page 5-5 to 5-11
Today
-Terminology
-Respiration
-Fermentation
-High energy bonds
-Terminal electron acceptors
- fermentation exercise
-The “Informal summary”
Terminology
-Polar = charged
-Non polar = uncharged
-Reduced =losing “O”
=acquiring “H atom”
=acquiring electrons
-Oxidized = acquiring “O atom”
=losing “H atom”
=losing electrons
-Hydrogen ion “H+” = proton
Terminology
-Metabolism: sum of total reaction that occur in a cell
and it consist of two types of processes
1- Catabolism:complex molecules are broken down
into simpler molecules with the
release of energy and reducing
power (electrons).
2- Anabolism:Synthesis of complex molecules from
simpler ones (building blocks) to form
cell structures and macromolecules,
this requires energy and often
reducing power.
Respiration
-it is defined as oxidation of a source of energy by
removal of electrons and donation to an inorganic
terminal electron acceptor.
-the terminal electron acceptor is “oxygen”, so it has
to happen in aerobic conditions.
Fermentation
-it is defined as an energy yielding process whereby
organic molecules serve as both electron donors
and electron accepters.
-it occur when there is no source for oxygen or when
the cell or organism evolved to live in an anaerobic
conditions
-some anaerobic conditions include deep levels of the
oceans, human and animal intestinal tracts or
air-proof flask
Who does what
-bacteria can either live in aerobic environment,
anaerobic environment or both (facultative anaerobic).
-yeast (baker yeast or Saccharomyces cerevisiae) is
a facultative anaerobic organism.
-human and animal cells generate energy by
respiration (human and animal skeletal muscle
cells can generate energy by fermentation).
-plant cells generate energy by respiration (when
oxygen is liberated from plants)
Fermentation versus respiration
A-where energy and reducing power are stored
-Energy carrier
-These are intermediate "high energy" carriers that
store this energy until the cell is ready to use it.
-Two main types
1- Adenosine TriPhosphate (ATP)
carrier of chemical
energy in the form
of high energy
phosphate bonds
Fermentation versus respiration
2-Nicotinamide Adenine Dinucleotide (NAD+)
is a carrier of hydrogen
and electrons and is
involved in many
oxidation-reduction
reactions in the cell
2e+H+
NAD+2e-+H+
NADH
Fermentation versus respiration
B- Do they have a common pathway
-glycolysis or Embden-Meyerhoff-Parnas pathway
(EMP) is a common pathway.
-it occur in the cytosol of the cell
2ADP+2Pi
2ATP
Glucose------------------->2 pyrovate
2NAD++4e-+2H+
2NADH
Fermentation versus respiration
C- what is the difference
-Basically, how the limited amount of NDA is
Regenerated and whether pyruvate molecules
undergo further catabolism.
-in fermentation, the electrons are passed to pyruvate
with the formation of end products that is the
excreted outside the cell.
Yeast cell
also Co2 is released
Fermentation versus respiration
Human and animal
skeletal muscle cell
Fermentation versus respiration
-in respiration
The reaction continues, where the pyruvate molecules
go into the citric acid cycle or Krebs cycle yielding
more ATP, NADH, and FADH.
-this occur in the matrix of mitochondria in
eukaryotes or in the cytosol in bacteria.
-the reduced molecules passes their electrons to O2
that serve as terminal electron acceptor. This process
is termed electron transport chain and occur at the
level of mitochondrial membrane in eukaryotes or
cell membrane in bacteria.
Fermentation versus respiration
Fermentation versus respiration
Fermentation versus respiration
-NADH get oxidized and the total process end
with the production of---Co2 + H2O.
-However, the electron transport chain result in
proton gradient outside the membrane, this gradient
is used to generate more ATP molecules using the
protonmotive force
Fermentation versus respiration
So, fermentation generate 2 ATP molecules, while
Respiration generate 36 ATP molecules
I got the picture
-start reading at the last paragraph of
page 29.
-Part B, add deionized water
up to 100ml
The informal summary
-it worth 18 points. It is due next week in lab.
-It is distributed as follow
1-abstract--- 6 points
2-introduction---3 points
3-experimental procedures--- 2 point
4-results----2 points
5-discussion--- 4 points
6-references---1
-it is a rehearsal for a formal one.