ATP moves from the mitochondrial matrix to the cytosol via the ATP-ADP translocase membrane transport protein. The translocase tightly couples the exchange of ADP for ATP as ATP exits. Uncouplers act to transport hydrogen ions across the inner mitochondrial membrane to the matrix without passing through ATP synthase. This short-circuits the proton gradient and results in energy being released as heat rather than being used to synthesize ATP. The malate-aspartate shuttle transfers reducing equivalents in the form of NADH from the cytosol into the mitochondrial matrix.

3. • ATP move from the mitochondrial matrix to the
cytosol via a specialized membrane transport protein,
“ATP-ADP translocase.”
• Translocase is tightly coupled to the exchange of ADP
for ATP as ATP exits.
3

4. Movement of ATP/ADP Through
translocase

5. These compounds
through increasing
the permeability of the IMM
Failure of formation of the electrochemical gradient
ATP formation stops while oxidation proceeds.
A- Uncouplers

7. They act by transporting H+ to
inside the mitochondria without
passing through F₀F1
And energy is released as heat.

8. 1. 2,4 dinitrophenol
2. Dinitrocresol
3. Snake venoms phospholipases
4. Pentachlorophenol
5. trifluorocarbonyl-cyanide phenyl
hydrazone

9. 2,4-dinitrophenol (DNP)
۞A small lipophilic molecule
۞A protein carrier
۞Can easily diffuse through
the IMM
۞Also used as drug to lose
weight
۞Due to many side effects
FOOD & DRUG
ADMINISTRATION has
banned this drug

10. : The lipophilic substance that promote
transport of ions across membranes.
e.g. antibiotic valinomycin facilitates the entry of H+
through the IMM.
2. Some endogenous compounds when increased act as
uncouplers: Bilirubin, Thyroxine & long chain free fatty acids
Bilirubin is, however, yet to be proved beyond doubt.

11. • It is considered as a
• It is present in the brown adipose tissue of newly
born, some people and hibernating animals.
• It allows protons to pass the mitochondrial
matrix without passing F0-F1 complex.
• No ATP is formed and energy is released in the
form of heat.

12. • Completely blocks F₀ so it inhibits
ATP synthesis
• Example: oligomycin (antibiotic)

14. • This is achieved by the compound

15. • Hibernating animals also uncouple ATP synthesis
to generate heat (nonshivering thermogenesis).
• In brown adipose tissue (which is very rich in
mitochondria), uncoupling protein (UCP) or
“thermogenin,” forms a pathway for the flow of
protons back into the matrix.
• This short circuits the proton gradient, generating
heat.
• Some flowers also generate heat this way to
voltalize fragrances that attract insects to fertilize
their flowers.

16. • The inner mitochondrial membrane is
impermeable to NADH. So the NADH produced in
cytosol can’t directly enter the mitochondria.
• Two different “shuttles” are operative to do this
job:
– Glycerol 3-phosphate shuttle (transfers electrons to
FADH2 .
– Malate-aspartate shuttle (transfers electrons to
NADH)
16

17. 17

18. 18
Aminotransferase
Aminotransferase
Cytosolic Malate
dehydrogenase
Mitochondrial
Malate
dehydrogenase

19. aspartate -ketoglutarate oxaloacetate glutamate
Aminotransferase (Transaminase)
COO
CH2
CH2
C
COO
O
COO
CH2
HC
COO
NH3
+
COO
CH2
CH2
HC
COO
NH3
+
COO
CH2
C
COO
O+ +

20. All enzymes participating in biological oxidation
belong to class oxidoreductase.
Major categories are:
1. Oxidases
2. Dehydrogenases
3. Hydroperoxidases
4. Oxygenases

21. • They catalyse the elimination of hydrogen
from substrate, which is mostly used to form
water.
• e.g. cytochrome oxidase, tyrosinase,
monoamine oxidase & some flavoprotiens.

22. Dehydrogenases
Catalyse reversible transfer of hydrogen from
on substrate to another
Thus bring about oxidation-reduction
reactions.

23. Examples
• NAD+ : e.g. glycerol 3-phosphate dehydrogenase
• NADP + : e.g. enoyl reductase
• FMN : e.g. NADH dehydrogenase
• FAD : e.g. succinate dehydrogenase
• Cytochromes: e.g. all Cytochromes of ETC (b, c & c1)
except terminal cytochrome complex belong to this
group.

24. Hydroperoxidases
• They prevent harmful effects of H2O2
produced by aerobic dehydrogenase.
• e.g. peroxidase and catalase

25. Oxygenases
• Catalyse direct incorporation of oxygen into
the substrate molecule.
• e.g. Dioxygenases and Monooxygenases

26. Electron transport in
Prokaryotes
• Lack mitochondria
• Set of e- carriers and enzymes of oxidative
phosphorylation are bound to inner cell
membrane.