Week 6 - Metabolism 2

Question 1

Why do we have mitochondria

Answer 1

Endosymbiosis - the prokaryotic mitochondria grows and the cell engulfed bacterium

Question 2

Describe the mitochondrial genome

Answer 2

Single circular chromosome in the matrix
37 genes in total

Question 3

How can mitochondrial DNA increase and decrease

Answer 3

Fusion increases it and fission decreases amount of mitochondrial DNA

Question 4

Describe transport of proteins in the mitochondria

Answer 4

Protein binds to import receptors, which binds to TOM complex and is inserted to membrane complex
Then TIM complex transloctes into the matrix where signal peptidase cleaves the signal off.

Question 5

How does pyruvate enter the mitochondria

Answer 5

Porins allow molecules up to 5000Da into intermembrane space. Pyruvate transported through porins.

Question 6

How do fatty acids enter mitochondria

Answer 6

Acyl CoA binds to carnitine to form acyl-carnitine which enters via acyl-carnitine translocase where the carnitine dissociates to leave Acyl-CoA

Question 7

How does NADH enter mitochondria

Answer 7

NAD reduces oxaloacetate to form malate, which enters and then is oxidised to reform NADH. The cycle then continues where aspartate leaves the membrane and forms oxaloacetate.

Question 8

Summarise the ETC

Answer 8

High energy electrons carried by NADH and FADH2 passed into chain
Energy lost by electrons as they move across
Energy used to pump protons across membrane, finally e goes to O and water is formed

Question 9

Describe complex I

Answer 9

Largest complex (NADH-CoQ reductase). NADH transfers electrons and NAD recycled. Complex I passes e along with 2 H to CoQ to form CoQH2. 4H pumped across membrane with energy

Question 10

Describe complex II

Answer 10

FADH2 is passed to complex II using Fe-S clusters, FAD recycled and CoQH2 is formed but not enough energy released to pump H across

Question 11

Describe complex III

Answer 11

CoQH2 donates electrons to complex III via Fe-S clusters and then cytochromes. The 2 protons then released into the space. 2 reduced cytochrome c is formed and 2 more H is pumped across the membrane

Question 12

What is the balanced equation for when the H is pumped and electrons are released

Answer 12

0.5 O2 + 2H+ + 2e- -> H2O

Question 13

What happens to the protons after the ETC

Answer 13

They enter ATP synthase, causing it to rotate and then exit into the matrix and ATP is regenerated