Question

Mitochondrial enzyme- cytochrome c oxidase activity lab

1. What are the four main components of complex 4 or cytochrome c oxidase?

2. What happened to the absorption 55nm after addition of mitochondrial preparation and why?

Answer 1

Answer:

1) The enzyme cytochrome c oxidase (or called as complex IV) is a large protein complex located in the membrane and found in mitochondrion of eukaryotes and in membrane of bacteria as well. It is an essential enzyme due to its regulatory role in the respiratory electron transport chain of mitochondria (or bacteria). It is the last enzyme which is located in the mitochondrial (or bacterial) membrane thus, catalyze the last step of the respiratory electron transport chain (oxidative phosphorylation).

It is a large protein, consists of 14 protein subunits and several metal prosthetic sites however, the four main components of Complex IV are:

1. Two hemes
2. A cytochrome a
3. A cytochrome a₃
4. Two copper centers (Cu_A and Cu_B centers)

The function of the enzyme complex IV involve to receives an electron from each of four cytochrome c molecules, and then transfers those electrons to one oxygen molecule. Thus, the molecular oxygen reduced to two molecules of water and ATP synthesized during the reaction. As during the catalysis, the enzyme binds to four protons from the inner aqueous phase of mitochondria (to make water). And four protons are translocated across the membrane which results to a transmembrane difference of proton electrochemical potential. And this proton electrochemical potential is than used by ATP synthase to synthesize the ATP.

Answer 2

Answer:

1) The enzyme cytochrome c oxidase (or called as complex IV) is a large protein complex located in the membrane and found in mitochondrion of eukaryotes and in membrane of bacteria as well. It is an essential enzyme due to its regulatory role in the respiratory electron transport chain of mitochondria (or bacteria). It is the last enzyme which is located in the mitochondrial (or bacterial) membrane thus, catalyze the last step of the respiratory electron transport chain (oxidative phosphorylation).

It is a large protein, consists of 14 protein subunits and several metal prosthetic sites however, the four main components of Complex IV are:

1. Two hemes

2. A cytochrome a

3. A cytochrome a3

4. Two copper centers (CuA and CuB centers)

The function of the enzyme complex IV involve to receives an electron from each of four cytochrome c molecules, and then transfers those electrons to one oxygen molecule. Thus, the molecular oxygen reduced to two molecules of water and ATP synthesized during the reaction. As during the catalysis, the enzyme binds to four protons from the inner aqueous phase of mitochondria (to make water). And four protons are translocated across the membrane which results to a transmembrane difference of proton electrochemical potential. And this proton electrochemical potential is than used by ATP synthase to synthesize the ATP.