MBC: Cell integrity: oxidative phosphorylation

Question 1

Where does it take place?

Answer 1

Inter-membrane space of mitochondria (inner membrane)

Question 2

Equations for the re-oxidation of NADH AND FADH2? Enthalpy changes for these reactions?

Answer 2

NADH+ H+ + 1/2O2 –>NAD+ +H2O
-223 kj/mol

FADH2+ H+ + 1/2O2 –> FAD+ H2O
-170kj/mol

Question 3

Definition of chemiosmosis?

Answer 3

The diffusion of H+ ions through the stalked particles down the proton gradient

Question 4

What does the ETC consist of ? Names?

Answer 4

ETC made of 4 membrane proteins and two mobile electron carriers.

membrane proteins are :
Complex I- NADH dehydrogenase
complex II- succinate dehydrogenase
complex III- Q- cytochrome C oxireductase
complex IV- cytochrome C oxidase

mobile carriers are:
co-enzyme Q (Ubiquinone)
Cytochrome C

Question 5

Roles of the 4 Complexes?

Answer 5

Accepts electrons from NADH and FADH2, and in doing so it accepts a proton too in an aqueous environment

Question 6

where does succinate dehydrogenase sit?

How does it communicate with CoQ?

Answer 6

inner mitochondrial membrane

uses FAD to directly interact with coenzyme Q

It uses FAD as a cofactor and can communicate directly with Coenzyme Q which is also in the membrane. As electrons are passed from FADH2 to Coenzyme Q it also picks up a pair of protons, thereby regenerating FAD and forming QH2.

Question 7

How is QH2 formed?

Name of the other product formed?

Answer 7

electrons passed from FADH2 to coenzyme Q,simultaneously picking up a pair of protons.

This regenerates FAD and forms QH2

Question 8

function of each membrane protein complex and mobile carriers?

Answer 8

There are four protein complexes (labeled complex I-IV) in the electron transport chain, which are involved in moving electrons from NADH and FADH2 to molecular oxygen.

Complex I establishes the hydrogen ion gradient by pumping four hydrogen ions across the membrane from the matrix into the intermembrane space.

Complex II receives FADH2, which bypasses complex I, and delivers electrons directly to the electron transport chain.

Ubiquinone (Q) accepts the electrons from both complex I and complex II and delivers them to complex III.

Complex III pumps protons through the membrane and passes its electrons to cytochrome c for transport to the fourth complex of proteins and enzymes.

Complex IV reduces oxygen; the reduced oxygen then picks up two hydrogen ions from the surrounding medium to make water.