CONCEPT OF RESPIRATORY CHAIN

-ANUSHA SHARMA

(@nu)

What is respiration?

 The act or process of inhaling and exhaling; breathing. Also called ventilation.

 The oxidative process occurring within living cells by which the chemical energy of organic molecules is released in a series of metabolic steps involving the consumption of oxygen and the liberation of carbon dioxide and water.

What does happen when respiration occurs? The oxygen which is in taken in

respiration . It helps in the process of catabolism

Catabolism: complex food molecules to small particles and get converted to acetyl coA

Respiration chain

The energy librated during the oxidation of food molecules is made available with in mitochondria as reducing equivalents (NADH and FADH2)

Mitochondria contains the respiratory chain which collects and transport reducing equivalents directing them to their final reaction with oxygen to form water

The passage of electrons in ETC is associated with the loss of free energy ,this free energy is utilized to generate ATP.

this respiration chain occurs in the mitochondria in the inner membrane( matrix, Cristal )

Components of respiration chain

The inner mitochondria membrane can be disrupted into 5 distinct respiratory or enzyme complex denoted as complex   I, II, III,  IV and V .

. NADH-Q oxidoreductase, succinate-Q reductase, Q-cytochrome c oxidoreductase, and cytochrome c oxidase are also called Complex I, II, III, and IV, respectively

And complex V is responsible for ATP synthesis

Pyruvate and alpha –ketoglutarate dehydrogenase and feS are other components

Complex of ETC

Complex 1 Has NADH binding site

NADH reductase activity NADH - NAD+

NADH ---> FMN--->FeS---> ubiquinone

ubiquinone ---> ubiquinone H2

4 H+ pumped/NADH

Complex II

succinate ---FAD—ubiquinone Contains coenzyme Q FADH2 binding site

FAD reductase activity FADH2 -- FAD

Complex III ubiquinone - ubiquinone ox while cyt C gets reduced Also contains cytochromes b

proton pump 4H+

Adds to gradient8 H+ / NADH 4 H+ / FADH2

Complex IVreduction of oxygencytochrome oxidasecyt a+a3 red ---> oxidized stateoxygen ---> water

2 H+ + 2 e- + ½ O2 -- 2 H2Otransfers e- one at a time to oxygen

Pumps 2H+ outTotal of 10 H+ / NADHTotal of 6 H+ / FADH2

TotalsProton gradient created as electrons

transferred to oxygen forming water

10 H+ / NADH6 H+ / FADH2

Complete mechanism