Lecture 12: Mitochondria

Question 1

When was the theory of symbiogenesis thought of allegedly?

Answer 1

1905

Question 2

Who allegedly thought of the idea of symbiogenesis?

Answer 2

Konstantin Mereschkowski

Question 3

Which cell in the body has the most mitochondria?

Answer 3

Liver cells

Question 4

Which cell in the body has the least mitochondria?

Answer 4

Red Blood Cell

Question 5

Describe the membrane structure of Mitochondria

Answer 5

Double membrane structure with an outer and inner layer.
The outer membrane is smooth whilst the inner layer is highly folded into cristae. This is to increase surface area

Question 6

Where is the mitochondrial matrix located?

Answer 6

In the inner membrane

Question 7

What does the mitochondrial matrix have?

Answer 7

Enzymes that are involved in the citric acid cycle and the conversion of pyruvate to acetyl-CoA which are important steps in ATP production

Question 8

What do mitochondria contain their own of?

Answer 8

Contains its own DNA and ribosomes, allowing them to synthesise some of their own proteins and replicate independently of the cell

Question 9

I’m gonna use this acronym OMM, what does it mean?

Answer 9

Outer mitochondrial membrane

Question 10

ToD: The OMM is semi-permeable?

Answer 10

True

Question 11

What is the OMM made out of?

Answer 11

Lipids
Proteins
Porins

Question 12

Describe the role of Porins in the OMM

Answer 12

Forms large channels that allow the passage of molecules (up to a certain size) in and out of the mitochondria

Question 13

What is the role of the OMM? (3)

Answer 13

Separates the contents of the mitochondria from the cytosol of the cell

Regulates the exchange of metabolites, ions and proteins between the mitochondria and the cytoplasm

Plays a role in mitochondrial fission and fusion

Initiates apoptosis

Question 14

Name two receptors involved in the import of proteins/metabolites into the mitochondria

Answer 14

Voltage-dependent anion channel (VDAC)
Translocase of the outer membrane (TOM)

Question 15

How does the outer membrane initiate apoptosis?

Answer 15

Releases pro-apoptotic proteins such as cytochrome c

Question 16

Where are the pro-apoptotic proteins stored in the mitochondria?

Answer 16

The intermembrane space

Question 17

How many genes does the mitochondrial genome code?

Answer 17

37

Question 18

How are mitochondria inherited?

Answer 18

Exclusively maternal

Question 19

How many protein-coding regions are there in the mitochondrial genome?

Answer 19

13

Question 20

How many tRNA genes are there in the mitochondrial genome?

Answer 20

22

Question 21

What is the total length of the mitochondrial genome in terms of base pairs?

Answer 21

16,569

Question 22

What is a protein translocator (in the mitochondrial context)?

Answer 22

A complex of proteins

Question 23

What is the role of a protein translocator? (2)

Answer 23

Maintains the function and integrity of mitochondria

Responsible for the import of proteins into the mitochondria as well as the proper insertion of these proteins into the mitochondrial membranes.

Question 24

What is the role of the TOM complex?

Answer 24

Imports nucleus-encoded mitochondrial precursor proteins into the intermembrane space

Question 25

What proteins are the SAM complex made of?

Answer 25

B-barrel proteins

Question 26

Where is the SAM complex found?

Answer 26

Common in the outer membrane

Question 27

What is the role of the TIM23 complex? (2)

Answer 27

Transports some of the proteins into the matrix, while helping to insert transmembrane proteins into the inner membrane

Question 28

What is the role of the TIM22 complex? (1)

Answer 28

Mediates the insertion of a sub-class of inner membrane proteins
e.g carrier proteins for ADP, ATP and Pi

Question 29

What is the role of the OXA complex?

Answer 29

Mediates the insertion of inner membrane proteins that are synthesised in the mitochondrion

Question 30

Proteins destined for the mitochondrial matrix are first synthesised where?

Answer 30

Cytosolic ribosomes

Question 31

What is the name of the protein that cytosolic ribosomes make for the mitochondrial matrix?

Answer 31

Precursor proteins

Question 32

What do precursor proteins have to direct them to the mitochondria?

Answer 32

N-terminal mitochondrial targeting sequence (MTS)

Question 33

What recognises the precursor proteins on the outer membrane?

Answer 33

Translocase of the outer membrane (TOM) complex

Question 34

How do the precursor proteins make it through the outer mitochondrial membrane

Answer 34

The TOM complex forms a protein-conducting channel

Question 35

After the precursor protein has passed through the TOM complex, where is it transferred next?

Answer 35

The inner membrane (TIM) complex on the inner mitochondrial membrane.

This forms a second protein-conducting channel that allows the precursor protein to cross the inner membrane

Question 36

What binds to the precursor protein in the mitochondrial matrix and assists in its folding and assembly?

Answer 36

The mitochondrial matrix-localised chaperones (Heat shock protein 70)
Co-chaperones

Question 37

What section of the protein needs to be cleaved off to mature the protein?

Answer 37

Mitochondrial Targeting Sequence

Question 38

Name the two peptidases needed to cleave the protein

Answer 38

Mitochondrial Processing Peptidase (MPP)
Mitochondrial Intermediate Peptidase (MIP)

Question 39

Where is the mature protein released into during the final stage?

Answer 39

Mitochondrial matrix