5.7.3: The structure of the mitochondria

Question 1

Describe the structure of mitochondria.

Answer 1

May be rod shaped, thread-like or spherical

• Diameter 0.5-1.0 um
• length 2-5 um

Question 2

What makes up the envelope?

Answer 2

• Inner and outer phospholipid membrane.
• Inner membrane is folded into cristae (singular crista) for a large surface area.
• Outer membrane is smooth

Question 3

What is embedded into the inner membrane?

Answer 3

• Proteins that transport electrons

- Protein channels associated with ATP synthase enzymes that allow protons to diffuse through them.

Question 4

What is the space between the inner and outer mitochondrial membranes of the envelope called?

Answer 4

Intermembrane space

Question 5

describe the mitochondrial matrix and its contents.

Answer 5

• Enclosed by the inner membrane
• Semi-rigid and gel-like
• Contains mitochondrial ribosomes
• Contains looped mitochondrial DNA
• Contains enzymes for the link reaction and Krebs cycle.

Question 6

The matrix is where the link reaction and the Krebs cycle take place. What does it contain?

Answer 6

• Enzymes that catalyse the stages of these reactions.
• Molecules of coenzymes NAD and FAD
• Oxaloacetate.
• Mitochondrial DNA (codes for enzymes and proteins)
• Mitochondrial ribosomes

Question 7

What is the composition of the outer membrane?

Answer 7

-contains proteins, some of which form channels or carriers that allow passage of molecules, such as pyruvate, into the mitochondrion.

Question 8

How is the lipid composition of the inner membrane different from the lipid composition of the outer membrane?

Answer 8

• The lipid bilayer is less permeable to small ions such as hydrogen ions (protons) than is the outer membrane.
• The folds, crista, give a large surface area for the electron carriers and ATP synthase enzymes embedded in them.

Question 9

How are the electron carriers arranged?

Answer 9

In electron transport chains which are involved in oxidative phosphorylation.

Question 10

What is the intermembrane space involved in?

Answer 10

Oxidative phosphorylation

Question 11

Why is it useful that the inner membrane is in close contact with the mitochondrial matrix?

Answer 11

-Molecules of reduced NAD and reduced FAD can easily deliver hydrogens to the electron transport chain.

Question 12

What does each carrier protein contain?

Answer 12

• A cofactor

- A non-protein haem group that contains an iron ion.

Question 13

How are electron carriers oxido-reductase enzymes?

Answer 13

The iron ion can accept and donate electrons because it can become reduced (Fe2+) by gaining an electron and oxidised (Fe3+) when donating the electron to the next electron carrier.

Question 14

Electron carriers also have a coenzyme, what does this do?

Answer 14

-Using energy released from the electrons, it pumps protons from the matrix to the intermembrane space.

Question 15

How does a proton gradient form across the membrane?

Answer 15

Protons accumulate in the intermembrane space.

Question 16

What does the proton gradient cause?

Answer 16

A flow of protons through the channels of the ATP synthase enzymes to make ATP.

Question 17

Describe ATP synthase.

Answer 17

• Large and protrude from the inner membrane into the matrix.
• Protons can pass through them.