4.2 Aerobic Respiration Flashcards
Decarboxylation rxn
Chem. rxn that removes a carboxyl group to form CO2
Dehydrogenation
The removal of a hydrogen atom from a molecule
Proton gradient
A difference in proton (H+ ion) concentration across a membrane
Proton-motive force
A force that moves protons because of a chemical gradient (electrochemical gradient) of protons across a membrane
Chemiosmosis
A process in which ATP is made using the energy of the electrochemical gradient and the ATP synthase enzyme
NAD+ and NADH
Nicotinamide adenine
dinucleotide
NAD+ can be reduced to form NADH
NADH can be oxidized to donate electrons
FAD and FADH2
Flavin adenine dinucleotide
FAD can be reduced to form FADH2
FADH2 can be oxidized to donate electrons
GTP
Guanosine triphosphate
Can be used to generate ATP
What to do with Pyruvate?
- The 2 molecules of Pyruvate that are
synthesized by Glycolysis still contain
about 75% of the energy stored in
Glucose - Pyruvate oxidation and the Citric Acid
Cycle help to harvest the remaining
available energy
Pyruvate Oxidation
- Carboxyl Group is removed – creates CO2
- NAD+ steals electrons from remaining molecule to
become NADH - Coenzyme A attaches to molecule to form Acetyl
CoA
2 Pyruvate + 2 NAD+ + 2 CoA –>
2 Acetyl CoA + 2 NADH + 2 H+ + 2 CO2
The Citric Acid Cycle
- Consists of 8 enzyme catalyzed
reactions - Used to create Energy Carrier
Molecules (NADH and FADH2) - Creates 2 ATP (1 per pyruvate)
- Converts the remaining carbon from
pyruvate into CO2
ETC
- Uses energy from electrons to pump protons
across the cell membrane to create a
concentration gradient - Accepts electrons from energy carriers
- Consists of 4 protein complexes and shuttle
molecules
Electron Transport Chain:
A series of
membrane bound molecules that transfers
electrons
Important Points to Remember
The cycle keeps moving because
oxaloacetate (the first reactant) is
regenerated
- Every step is catalyzed by reactions
- GTP (guanosine triphosphate) is used to
make ATP
- NADH and FADH2 will be used later to
make ATP
What enters the ETC?
All of the Carbon from Glucose
has already been turned into
Carbon Dioxide
NADH and FADH2 are now
used to power the ETC
Complex I (NADH Dehydrogenase)
- Oxidizes NADH (loses electrons)
into NAD+ - Hydrogen atoms are pumped
across the membrane as
electrons move through the
complex
Complex II (Succinate Dehydrogenase)
FADH2 is oxidized by complex II
and donates electrons
Energy from electrons is used to
pump protons across the
membrane
Ubiquinone
- Ubiquinone (UQ) is used to move
electrons from complex I and
complex II to Complex III - Ubiquinone is a hydrophobic
molecule found within the inner
mitochondrial membrane
Complex III (Cytochrome Complex)
- Electrons transferred from
Ubiquinone move to Complex III - Complex III transfers the electrons to
Cytochrome C (another electron
shuttle) which can then move
electrons to Complex IV
Complex IV (Cytochrome Oxidase)
- Electrons are transferred from
Cytochrome c to complex IV - Electrons combine with Hydrogen ions
and an oxygen atom to form water - Movement of electrons drives the
pumping of more Hydrogen across the
cell membrane
Increasing Electronegativity
- The electrons move through the ETC
because each complex is more
electronegative than the last - Oxygen is the final electron acceptor
and has the highest electronegativity
(thus oxygen drives the process)
Chain Reaction
- Oxygen causes complex IV to steal
electrons from complex III which then
steals electrons from complex II which
then steals electrons from complex I
which then steals electrons from NADH - This chain reaction is what ultimately
drives the ETC
Chemiosmosis
- Proton gradient created by the
ETC drives ATP synthesis - Protons flow through ATP
Synthase (a membrane
protein) which phosphorylates
ADP
Uncoupling Electron Transport and
Chemiosmosis
- Special Uncoupling Proteins are used as
an alternative route for protons to flow
back into the matrix of the
mitochondria - Instead of producing ATP these proteins
help convert the energy into thermal
energy to keep animals warm
