ETC Flashcards
define Substrate level Phosphorylation
Phosphorylation or high energy phosphate bond
formation occurs at substrate level
* It produces ATP directly
Define high energy compounds with examples
Substances that release energy higher than ATP
Phosphoenolpyruvate – 14.8 kcal/mol
1,3-bisphoshoglycerate – 11.8 kcal/mol
Creatine phosphate – 10.3 kcal/mol
ATP – 7.3 kcal/mol
energy released by Phosphoenolpyruvate
14.8 kcal/mol
energy released by 1,3-bisphoshoglycerate
11.8 kcal/mol
energy released by Creatine phosphate
10.3 kcal/mol
energy released by ATP
7.3 kcal/mol
SUBSTRATE LEVEL PHOSPHORYLATION IN SKELETAL MUSCLE
Creatine Phosphate- “energy rich” phosphate is formed from ATP in muscle
- can regenerate ATP as needed
net ATP made by oxidative phosphorylation
glycolysis- 6 ATP from 2 NADH
transition reaction- 6 ATP from 2 NADH
krebs cycle- 18 ATP from 6 NADH & 4 ATP from 2FADH2
total= 34 ATP
SHUTTLE SYSTEMS FOR THE TRANSPORT OF NADH
- Malate aspartate shuttle (malate shuttle)
- Glycerol 3-phosphate shuttle - in muscle and brain
define ELECTRON TRANSPORT CHAIN
Is the transfer of electrons from NADH and FADH2 to oxygen through series of e transporter on the inner mitochondria membrane
The electron derived combine with O2 and
the energy released from these oxidation-reduction process is used to drive the synthesis of ATP from ADP
COMPLEX I
‘NADH dehydrogenase’
- read notes
where is the H+ pumped into
from matrix to intermembrane space
what is the e flow in NADH dehydrogenase?
NADH-FMN- FE-S -Q
role of ubiquinone
-mobile e carrier
- transfers equivalents from flavoproteins to cytochromes
complex 2
succinate dehydrogenase
e flow in succinate dehydrogenase
suc- FAD- FeS- CoQ
complex iii and its e flow
cytochrome b-c1
CoQ —> Cyt b —> Cyt c1 —-> Cyt c
complex iv and its e flow
cytochrome C oxidase
cyt.c- cyt.a-a3 -O2
what is the terminal e acceptor
oxygen
at which complex water is formed and state the eq
cytochrome C oxidase
4H+ + 4e+ O2= 2H2O + ENERGY
which complex directly recieves FADH2
complex II
describe cytochrome
protein with heme grp( porphyrin ring +iron)
reversible state of iron depending on electron
fe2+- ferrous
fe 3+- ferric
content of each complex
I-FMN, FeS,Q,flavin prosthetic grp
II-FAD centre, FeS
III-heme grp ( porphyrin ring+ iron), FeS, Cyt b,Cyt c1
IV- cytochromes a+a3,Cu atoms,heme a & heme a3
THE ETC MECHANISM
1.High-energy electrons from NADH and FADH2 are passed along the ETC from one carrier protein to the next.
2.During electron transport, H+ ions build up in the intermembrane space, so it is positively charged.The other side of the membrane, from which those H+ ions are taken, is now negatively charged.
3. At the end of the chain, an enzyme combines these electrons with H+ ion and O2 to form water.
4. The inner membranes of the mitochondria contain ATP synthase.
5. As H+ ions escape through channels into these proteins, the ATP synthase
spins.
6. As it rotates, the enzyme grabs a low-energy ADP, attaching a phosphate (Pi), forming high-energy ATP.
The energy for the pumping comes from the coupled oxidation- reduction reactions
How is ATP generated
- The inner membranes of the mitochondria contain ATP synthase.
- As H+ ions escape through channels into these proteins, the ATP synthase
spins. - As it rotates, the enzyme grabs a low-energy ADP, attaching a phosphate (Pi), forming high-energy ATP.
The energy for the pumping comes from the coupled oxidation- reduction reactions
OXIDATIVE PHOSPHORYLATION definition
Synthesis of ATP from ADP (phosphorylation) that occur when NADH and FADH2 are oxidized by ETC (oxidation) through H+ gradient.
how do the protons in the intermembrane space enter the matrix?
through ATP synthase
where is ATP synthase located?
the inner mitochondrial membrane (IMM)
ATP SYNTHASE
“knob-and-stalk structure
* F1(knob) contains the catalytic subunits for ATP production
* F0 (stalk) has a proton channel which spans the membrane
Function:
synthesize ATP from ADP and inorganic phosphate (Pi) that generated by the proton motive force of the ETC
MECHANISM OF ATP SYNTHASE
- Protons pass through F0 unit
- Passing of proton, F1 unit become active
- Activated F1 catalyzes phosphorylation of ADP and Pi and produces ATP
CHEMIOSMOSIS
the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration.
CHEMIOSMOTIC HYPOTHESIS:
MITCHELL HYPOTHESIS (4)
Free energy generated by the transfer of electrons by ETC is used to produce ATP from ADP and Pi.
ETC is coupled to ADP phosphorylation by pumping of H+ across inner mitochondrial memb from matrix to space.
Generation of electrical (H+) and chemical (pH) gradient across the inner mitochondrial membrane (IMM)
Pumping of protons into the matrix through complex V
P:O ratio
Number of ATP made per O atom reduced
P/O for 1 NADH = 3:1
P/O for 1 FADH2 = 2:1
describe Electron Transport inhibitors
Inhibit ETC and ATP synthesis (as they are coupled)
* Site specific inhibitors
* Prevent passage of electrons by binding to
specific component of ETC
* Block oxidation-reduction reaction
state inhibitors of each complex
Complex I: Rotenone
Complex II: Carboxin
Complex III: Antimycin A
Complex IV: , Sodium azide,Cyanide
Carbon monoxide
describe ATP synthase inhibitors
-Oligomycin: Binds to Fo and close the proton channel.
-Atractyloside: Inhibits ATP-ADP exchange
describe uncouplers
- compounds that form channels for H+ to re-enter mitochindrial matrix without energy being captured as ATP
- energy is released as heat( non-shivering thermogenesis)
- oxidation is uncoupled from phosphorylation becoz energy cannot be trapped as ATP
state uncouplers
1.Thermogenin (natural)
– brown adipocytes (mammals)
- 90% of energy produced during ETC dissipated as heat to maintain body temp in infants
2. 2,4-dinitrophenol (2,4-DNP) -synthetic uncoupler
- H+ carrier that readily diffuses through mitochondrial membrane
3. High dose of aspirin, salicylates
