Week 5: Mitochondria

Question 1

What is the structure of mitochondrial DNA (mtDNA)?

Answer 1

Circular, 16.6 kb, no introns

Mitochondrial DNA is distinct from nuclear DNA in its structure and organization.

Question 2

How many genes does mitochondrial DNA (mtDNA) code for?

Answer 2

37 genes:
* 22 tRNAs
* 2 rRNAs
* 13 proteins (MRC subunits)

MRC subunits refer to the proteins that are part of the mitochondrial respiratory chain.

Question 3

What type of inheritance is associated with mitochondrial DNA (mtDNA)?

Answer 3

Maternally inherited

This means that mtDNA is passed down from mother to offspring.

Question 4

Is mitochondrial DNA (mtDNA) synchronized with cell division?

Answer 4

No

Mitochondrial DNA replication is independent of the cell cycle.

Question 5

What is homoplasmy in the context of mitochondrial DNA?

Answer 5

Identical mtDNA

Homoplasmy indicates that all mtDNA in a cell is the same.

Question 6

What is heteroplasmy in the context of mitochondrial DNA?

Answer 6

Mix of mutant and wild-type mtDNA

Heteroplasmy can lead to a variety of mitochondrial disorders.

Question 7

True or False: Mitochondrial DNA contains introns.

Answer 7

False

Mitochondrial DNA is unique in that it lacks introns.

Question 8

What is the process through which ATP is synthesized?

Answer 8

Oxidative Phosphorylation (OXPHOS)

OXPHOS is a key metabolic pathway that generates ATP using energy derived from the electron transport chain.

Question 9

What is the first key step in ATP synthesis during OXPHOS?

Answer 9

Electron Transport Chain (ETC)

The ETC involves the transfer of electrons from NADH to various proteins in the inner mitochondrial membrane.

Question 10

What does NADH donate to the Electron Transport Chain?

Answer 10

Electrons

NADH is generated in the Krebs cycle and serves as a crucial electron donor in the ETC.

Question 11

What does the Electron Transport Chain create across the inner membrane?

Answer 11

Proton gradient

This gradient is essential for driving ATP synthesis via ATP synthase.

Question 12

Name one proton pump involved in the Electron Transport Chain.

Answer 12

NADH-ubiquinone oxidoreductase

Other proton pumps include Succinate dehydrogenase, Ubiquinone-cytochrome c oxidoreductase, and Cytochrome c oxidase.

Question 13

What drives ATP synthase in chemiosmotic coupling?

Answer 13

Proton-motive force

The proton-motive force is generated by the proton gradient created during the ETC.

Question 14

What does ATP synthase convert ADP to?

Answer 14

ATP

ATP synthase is an enzyme that synthesizes ATP from ADP and inorganic phosphate using the energy from the proton gradient.

Question 15

Fill in the blank: The input for the reaction involving ATP synthesis includes _______.

Answer 15

Acetyl CoA + O2 + ADP

This reaction also produces CO2 and H2O as byproducts.

Question 16

True or False: The output of the ATP synthesis reaction includes CO2 and H2O.

Answer 16

True

These are the byproducts of the reaction where Acetyl CoA, O2, and ADP are converted into ATP.

Question 17

What is the primary function of mitochondria?

Answer 17

Producing ATP through aerobic metabolism

Mitochondria are often referred to as the power plants of the cell.

Question 18

Describe the structure of mitochondria.

Answer 18

Double membrane (outer and inner), inner membrane forms cristae, contains matrix and intermembrane space

The cristae increase the surface area for ATP production.

Question 19

What is the dynamic nature of mitochondria?

Answer 19

Undergoes fission and fusion, functions as a network interacting with other organelles

This dynamic behavior allows mitochondria to adapt to the cell’s energy needs.

Question 20

Fill in the blank: Mitochondria are known as the _______ of the cell.

Answer 20

power plants

Question 21

True or False: Mitochondria have a single membrane structure.

Answer 21

False

Mitochondria have a double membrane structure.

Question 22

What structures increase the surface area of the inner mitochondrial membrane?

Answer 22

Cristae

Cristae are folds of the inner membrane that enhance ATP production.

Question 23

What are the two distinct spaces within the mitochondria?

Answer 23

Matrix and intermembrane space

The matrix contains enzymes for the Krebs cycle, while the intermembrane space is involved in the electron transport chain.

Question 24

What is apoptosis?

Answer 24

Programmed cell death triggered by the release of cytochrome c from mitochondria

Apoptosis involves a caspase cascade leading to cell death.

Question 25

What is necrosis?

Answer 25

Inflammatory cell death

Necrosis is often caused by injury or disease.

Question 26

Who won the Nobel Prize in 1978 and for what contribution?

Answer 26

Peter Mitchell for the chemiosmotic theory

The chemiosmotic theory explains how ATP is generated in mitochondria.

Question 27

What is the size range of mitochondria?

Answer 27

1-2 um

Mitochondria are typically found in large numbers within cells.

Question 28

How many mitochondria can be found per cell?

Answer 28

10-100,000 per cell

Mitochondria occupy approximately 25% of the cytoplasm.

Question 29

What is the composition of the outer mitochondrial membrane?

Answer 29

50% lipid/protein, permeable to molecules <10 kDa

This allows small molecules to pass through easily.

Question 30

What is the composition of the inner mitochondrial membrane?

Answer 30

20% lipid/80% protein, houses respiratory proteins

The inner membrane is critical for ATP synthesis.

Question 31

Fill in the blank: Mitochondria release _______ to trigger apoptosis.

Answer 31

cytochrome c

This release initiates the caspase cascade.

Question 32

True or False: Necrosis is a form of programmed cell death.

Answer 32

False

Necrosis is characterized as inflammatory cell death.