Mitochondria

Question 1

True or False: most scientists believe that the mitochondria evolved from the ER.

Answer 1

False. The dominant theory is that an early cell engulfed a prokaryote that became the mitochondria.

Question 2

How many membranes does the mitochondria have?

Answer 2

Two. An inner and outer.

Question 3

The mitochondria has porins for transporting molecules. Are they on the inner or outer membrane?

Answer 3

The outer. It is permeable to ions and small molecules, while the inner is impermeable.

Question 4

What are cristae?

Answer 4

They are folds in the inner membrane that increase surface area.

Question 5

Where does the citric acid cycle occur in the mitochondria?

Answer 5

The mitochondria matrix.

Question 6

True or False: there are ribosomes in the mitochondria.

Answer 6

True. They are used to translate mitochondrial DNA.

Question 7

What is the typical result of defects in the mitochondrial network?

Answer 7

The progression of numerous neurodegenerative diseases (e.g., Parkinson’s, Alzheimer’s)

Question 8

What is the mitochondrial network structured from?

Answer 8

A network of tubules that are mobile and can fuse with one another.

Question 9

Explain the difference between mitochondrial fission and fusion.

Answer 9

Fission is a breakdown of one into two, and fusion is the combination of two into one.

Question 10

True or False: matrix-destined proteins possess unique targeting presequence.

Answer 10

True

Question 11

What is the function of cytosolic chaperones in mitochondrial import?

Answer 11

Its job is to recognize proteins to be imported into the mitochondria

Question 12

True or False: matrix-destined proteins enter the mitochondria completely folded.

Answer 12

False. In order to pass into the porin, they must be partially unfolded.

Question 13

What is the name of the complex used to recognize a matrix protein’s N-terminal presequence at the surface of the mitochondria?

Answer 13

The TOM complex

Question 14

Where is the matrix protein passed after it has been recognized by the TOM complex at the surface of the mitochondria?

Answer 14

To the TIM23 complex in the inner membrane.

Question 15

True or False: the TOM complex and the TIM23 complex are physically connected.

Answer 15

True. This allows for the protein to translocate across the outer and inner membrane sequentially.

Question 16

What is the general charge on the matrix protein presequence, and why is it important?

Answer 16

It is very positively charged. The TOM and TIM23 complexes are driven by electrochemical charge, which is how the protein can move through them.

Question 17

What is the function of the TIM22 complex in the inner membrane?

Answer 17

It inserts proteins straight from the TOM complex into the inner membrane.

Question 18

Explain the function of mtHsp70 (a chaperone) in the mitochondria.

Answer 18

It pulls proteins into the matrix once they have successfully passed through the membrane, and prevent them from backsliding into the cytosol again.

Question 19

True or False: after a protein has entered the matrix, its presequence is snipped off.

Answer 19

True. MPP is the peptidase that cleaves it.

Question 20

Explain how the import of PINK1 protein into the mitochondria is linked to Parkinson’s.

Answer 20

Normally, PINK1 enters the matrix via TOM. For a person with Parkinson’s, PINK1 can’t enter the matrix. It accumulates in the cytosol, and signals autophagy to begin. This eventually induces apoptosis.