Topic 4, Lecture 2

Question 1

Describe the anatomy of the mitochondria.

Answer 1

Outer membrane, intermembrane space, inner membrane, matrix

Question 2

Describe the inner mitochondrial membrane

Answer 2

The inner membrane has cristae (folds) to allow for the electron transport chain (ETC). Because of the ETC, the inner membrane is about 75-80% proteins.

Question 3

Describe the outer mitochondrial membrane.

Answer 3

The outer membrane is not attached to the inner membrane like the nucleus. The outer membrane is composed of about 50% proteins and 50% lipids.

Question 4

Describe the mitochondrial matrix.

Answer 4

Hardest space to get to because we have to cross all of the other membranes.

Question 5

Describe mitochondrial “pores”.

Answer 5

Not really pores but channels. Made up of alpha helices and beta sheets.

Question 6

Describe the mitochondrial signal sequence.

Answer 6

The mitochondrial signal sequence is on the amino terminus, its long, no acidic amino acids, gets cleaved by signal peptidase.

Question 7

Describe the relation between alpha helices and the mitochondrial signal sequence.

Answer 7

Alpha helices make a full turn every 3.6 amino acids. There is a basic amino acid about every 3.6 amino acids on the mitochondrial signaling sequence. This causes the sequence to be amphipathic.

Question 8

Amphipathic

Answer 8

One side polar and one side nonpolar

Question 9

Is mitochondrial protein transport post- or co-translational?

Answer 9

Post-translational

Question 10

Do proteins enter the mitochondria folded or unfolded?

Answer 10

Unfolded

Question 11

How do mitochondrial proteins enter the mitochondria unfolded if the process is post-translational?

Answer 11

Cytosolic Hsp70 is bound to the protein to prevent folding.

Question 12

Describe the anatomy of the TOM complex.

Answer 12

TOM has a translocation channel and receptors

Question 13

What is the name of the location of where TIM23 moves up to touch the TOM complex?

Answer 13

Contact Site

Question 14

Does the mitochondrial signaling sequence get cleaved? If so, how?

Answer 14

Yes, signal peptidase

Question 15

Does the mitochondrial signaling sequence get cleaved? If so, how?

Answer 15

Yes, signal peptidase

Question 16

Describe the function of Hsp70.

Answer 16

Bind and stabilize unfolded or partly folded proteins to prevent aggregation, acts co-translationally

Question 17

What is the energy source for mitochondrial protein transport?

Answer 17

ATP hydrolysis of cytosolic and mitochondrial Hsp70 and the Proton Motive Force

Question 18

Why do we need to hydrolyze ATP in the mitochondrial matrix?

Answer 18

To power translocation, to keep the protein from going back out TIM23

Question 19

When does the proton motive force occur?

Answer 19

During cellular respiration

Question 20

OIL RIG

Answer 20

Oxidation is lose, reduction is gain

Question 21

Describe MIA40

Answer 21

Mia40 is reduced and oxidizes the imported protein. When this happens, the sulfur atoms on the cysteines are available for disulfide bonding.

Question 22

Why is disulfide bonding important for proteins in the intermembrane space?

Answer 22

The disulfide bonds make the protein too big to get back out through the TOM complex but still small enough to get through TIM23

Question 23

Oxidant

Answer 23

Something that removes and/or accepts electrons

Question 24

Signal Anchor

Answer 24

Some mitochondrial proteins have an extra sequence to decide which path they take, transmembrane domain/segment

Question 25

Discuss why transmembrane proteins are not solids.

Answer 25

Lateral exit sites, which allow proteins to be embedded into the membrane

Question 26

Which transmembrane protein puts proteins in the inner membrane to function in the intermembrane? What does it use to do that?

Answer 26

TIM23, transmembrane segment

Question 27

Which transmembrane protein puts proteins fully into the inner membrane? What does it use to do that?

Answer 27

TIM22, intermembrane space chaperones

Question 28

Which transmembrane protein puts mitochondrial proteins into the inner membrane?

Answer 28

OXA Complex

Question 29

Does OXA only work on mitochondrial encoded proteins?

Answer 29

No, OXA can also place nuclear encoded proteins

Question 30

How do intermembrane space proteins get put there?

Answer 30

By being embedded into the inner membrane, and then cleaved by a protease

Question 31

How do we get proteins into the outer membrane?

Answer 31

SAM Complex

Question 32

What are some examples of proteins that get embedded by the SAM complex?

Answer 32

Beta barrels, and alpha helices

Question 33

Describe the peroxisome signal sequence

Answer 33

Short, Carboxy terminus, permanent

Question 34

Is peroxisomal protein transport post- or co-translational?

Answer 34

Post-translational

Question 35

List the parts to peroxisomal transport.

Answer 35

Pex 5, 14, 2,10,12, Docking/Translocation Model

Question 36

How do we create peroxisomes?

Answer 36

Fission from the ER