Loading....
Coupon Accepted Successfully!

Biochemistry

Open Flashcards

Carbohydrates

Question
38 out of 78
 

Which of the following is an effect of dinitrophenol on oxidative phosphorylation.



A Inhibition of cytochrome b

B Blockade of both electron transport and ATP synthesis

C Inhibition of ATP synthesis with normal electron transport

D Inhibition of electron transport but not ATP synthesis.

Ans. C Inhibition of ATP synthesis with normal electron transport

Fig.: Proposed sites of inhibition (-) of the respiratory chain by specific drugs, chemicals, and antibiotics. The sites that appear to support phosphorylation. BAL, dimercaprol. TTFA is an Fe-chelating agent. Complex, NADH: ubiquinone oxidoreductase; complex II, succinate: ubiquinone oxidoreductase; complex Ill, ubiquinol: ferri cytochrome c oxidoreductase; complex IV, ferr cytochrome C: oxygen oxidoreductase.

Respiratory chain and inhibition (Must read)

a. Component of the respiration chains are arranged in order of increasing Redox-potential.

b. H+ or electron (e) (Reducing equivalents) flow through the chain in steps form more electro negative

component to the more electro +ve through a redox potential 1.1 volt from NAD+/NADH to O2/2H2O.

c. ‘Q’ or Ubiquinone or, Co-enzyme Q — linking between flavoprotein and cyt. b. It is mobile; Q is

constituent of the mitochondrial lipid. Structure of the Q is similar to vit. K and vit E, and planto quinone (All characterized by Poly-iso-pyrenoid side chain.* cyt. c:- is only soluble cyt.)

d. One glucose, on complete combustion gives — 2870 KJ energy but only 68% of the energy is conserved or captured in the form of ATP.

NAD — dehydrogenase 3ATP, P: O ratio =2.5

Flavoprotein (FAD) — dehydrogenase = 2ATP, P:O ratio =1.5

e. Conditions limiting the rate of Respiration:

5-states:

State 1 — Availability of ADP and substrate

State 2— Availability of substrate only

State 3 — The capacity of the respiratory chain itself when all substrates and components are present in saturating amounts.

State 4 — Availability of ADP only. (State 4 is most important, generally most cells in the resting state are instate 4, and respiration is controlled by the availability of ADP)

State 5 — Availability of O2 only.

6. Inhibitors of Respiratory chains : 3—types: -

a. Inhibitors of respiratory chain proper

b. Inhibitors of oxidative phosphorylation

c. UN couplers of oxidative phosphorylation.

a. Barbiturate (Amobarbital), Piecrcidin A and Rotenone (Insecticide and fish poisons): - they prevent oxidation of substrate that communicates directly with respiratory chain via — NAD-linked deHase by blocking the transfer from FeS to Q

b. Dimercaprol (BAL) and Antimycin A: - inhibit respiratory chain between cyt. b and cyt C

c. H2S, CO. CN- (cyanide): - inhibits cyt. Oxidase (cyt. aa3) and totally arrest the respiration.

d. Caboxin and TTFA: - inhibits transfer of ‘H+ or ‘e’ from succinate deHase to Q; whereas Malonate is a competitive inhibitor of succinate deHase

e. Oligomycin — block oxidation and phosphorylation

f. UN couplers to dissociate oxidation in the Respiratory chain from phosphorylation.

Eg. Dinitrophenol: - Oxidation proceeds without phosphorylation i.e. electron transfer occurs

(oxidation) without ATP formation (phosphorylation)

Dinitrocresol, penta chlorophenol and CCCP inhibit in similar manner as dinitrophenol.

CCCP (m-chloro carbonyl cyanide phenylhydrazone) is 100 times as active as dinitrophenol.

g. Atractyloside: - inhibits oxidative — phosphorylation, it is considered to inhibits the transport of ADP into the mitochondria and of ATP out of the membrane.

h. Malate shuttle: - for transfer of reducing equivalents (H+ or ‘e) from cytosol into mitochondria consists of keto glutarate transporters, glutamate-Aspartate transporter, malate de Hase and transaminase.

i. MELAS (Mitochondrial myopathy, encephalopathy Lactic acidosis, and seizures (- is an inherited condition due to NADH: Ubiquinone oxidoreductase (complex —P) or cyt. aa3 deficiency.

Carbohydrates Flashcard List

78 flashcards
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
25)
26)
27)
28)
29)
30)
31)
32)
33)
34)
35)
36)
37)
38)
39)
40)
41)
42)
43)
44)
45)
46)
47)
48)
49)
50)
51)
52)
53)
54)
55)
56)
57)
58)
59)
60)
61)
62)
63)
64)
65)
66)
67)
68)
69)
70)
71)
72)
73)
74)
75)
76)
77)
78)