Oxidative phosphorylation, fermentation Flashcards
Does FADH2 and NADH donate an equivalent number of electrons?
yes a number of 2 electrons for oxygen reduction, the electron transport chain provides about one-third less energy for ATP synthesis when the electron donor is FADH2 rather than NADH.
whats the difference between FADH2 and NADH
FADH2 adds its electrons to the electron transport chain from within complex II, at a lower energy level than NADH does.
Electrons from NADH passed among proteins of the ETC with the help of…
coenzyme Q and cytochromes (iron atom) to O2
Does ETC generate ATP directly?
NO
Cytochromes
- most of the remaining electron carriers between ubiquinone and oxygen are proteins called cytochromes.
- their prosthetic group called a heme group has an iron atom that accepts and donates electrons.
Electron transport chains has several types of cytochromes…
each a different protein with a slightly different electron carrying heme group
chemiosmosis
process, in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work such as the synthesis of ATP
-use of a H+ gradient to drive work
Osmosis
flow of H+ across a membrane
ETC + Chemiosmosis =
oxidative phosphorylation
ETC Chemiosmosis summary
- NADH( glycolysis and TCA) and FADH2 (TCA) transfer electrons to ETC
- ETC complexes located on the mitochondrial inner membrane
- series of redox reactions transfers electrons
- H+ pumped into inter-membrane space
- electrons delivered to 1/2 O2
Proton motive force (inter membrane space-> mitochondrial matrix)..
drives ATP synthesis
Most ATP is produced by….
oxidative phosphorylation is the mitochondrion
Supply of pyruvate to mitochondria
supply can limit rate of oxidative phosphorylation (production of NADH, FADH2 by Krebs cycle)
Transport protein
mitochondrial pyruvate carrier (MPC)
yeast->mammals
normal chemiosmosis
protons re-enter the mitochondrial matrix through ATP synthase, generating ATP
-the are coupled (mitochondria)
uncoupled mitochondria
in some situations/species/tissues:
proton gradient “uncoupled from ATP synthesis”
Chemiosmosis is an energy-coupling mechanism…
that used energy stored in the form of and H+ gradient across a membrane to drive cellular work
ex. in mitochondria it comes from exergonic redox reactions and ATP synthesis is the work performed
uncoupling protein
a mitochondrial inner membrane protein that can dissipate the proton gradient before it can be used to provide the energy for oxidative phosphorylation
also called leaky mitochondria.
brown fat (Uncoupled)
- in neonates and hibernators, brown from high density of mitochondria
- high density of UCP in mito. inner membrane
- generate heat without shivering
what does uncoupled mitochondria do?
- oxidize NADH from glycolysis and TCA but produce no ATP
- only 4 (from glycolysis and Krebs cycle)/32 possible ATP from glucose molecule
- inefficiency in conversions of ingested macromolecules to energy
any given amount of food generates less ATP…
Less excess energy to be stored
some poisons uncouple mitochondria
malonate-make the inner membrane permeable to ions including protons
eg. 2,4 dinitrophenol
Rotenone
blocks NADH dehydrogenase
reactive oxygen species
chemically reactive molecules containing oxygen.
ex. oxygen ions and peroxides
catabolism of other substrates
other organic molecules can be the source of electrons for cellular reparations
catabolism of other substrates: carbohydrates
glycolysis accepts a wide range of carbohydrates
catabolism of other substrates: proteins
- digested to amino acids
- feed glycolysis or the citric acid cycle
- ammonia produced- nitrogenous waste
catabolism of other substrates: fats/lipids
-digested to glycerol and generates acetyl CoA by beta oxidation
Anabolism (biosynthesis)
use of small molecules to build other substance
- directly from food
- from glycolysis
- from the citric acid cycle
some organisms that normally use oxidative phosphorylation..
can produce some ATP in the absence of oxygen
