Mitochondria

Question 1

Describe the structure of mitochondria

Answer 1

• Double membrane (inner/outer)
• Intermembranal space separating 2 membranes
• Matrix: inner lumen
• Contains membrane bound proteins
• Cristae: inner membrane folds

Question 2

Give examples of physical stimuli that can cause morphological changes within mitochondria

Answer 2

• apoptosis
• Ca2+ transfer
• Cell cycle
• Nutrient saturation

Question 3

What is the advantage of having cristae in the mitochondria?

Answer 3

Increases the surface area of membrane so more proteins are available for oxidative phosphorylation to occur
More ATP produced faster

Question 4

What are co factors?

Answer 4

Molecules that associate with proteins/enzyme to aid their function

Question 5

Where are proteins found in the mitochondria synthesised?

Answer 5

In the cytoplasm and transported to the mitochondria

Question 6

Which other structure is closely associated with mitochondria?

Answer 6

Mitochondria associate strongly with microtubules allowing them to change shape regularly

Question 7

How is mtDNA inherited?

Answer 7

Genes are inherited cytoplasmically from the mother to offspring via the egg cell

Question 8

How can we view the 3D structure of mitochondria ?

Answer 8

Via tomograms

Question 9

What processes occur in order to generate of ATP

Answer 9

e- transport chain
oxidative phosphorylation
citric acid cycle

Question 10

What causes mitochondrial morphology to change?

Answer 10

Mitochondria changes shape in response to physical stimuli

Question 11

What are the functions of mitochondria?

Answer 11

• Breakdown of fatty acids -> acetyl CoA
• Decarboxylation of pyruvate -> acetyl CoA
• Citric Acid Cycle (in matrix)
• Oxidative Phosphorylation
• Thermogenesis
• Apoptosis

Question 12

What is significant about the mitochondrial genome?

Answer 12

Mitochondria have a small genome subset that are encoded for and synthesised in the mitochondrial matrix
- differs from nuclear genome

Question 13

What is Beriberi disease?

Answer 13

Neurological & cardiovascular disease

Caused by a Vit. B1 deficiency (thiamine)

Question 14

How are peroxisomes formed from the ER?

Answer 14

1. Vesicles form off ER membrane
2. Vesicles grow via uptake of peroxisomal proteins and lipids from cytosol
3. fission occurs
4. Contain peroxisomal targeting signal which binds to receptors enabling transport to peroxisome

Question 15

What induces mitochondrial tubulation?

Answer 15

Starvation causes mitochondria to elongate and fuse with each other to prevent getting degraded through the autophagy pathway

Question 16

Which cells in the body are mitochondria commonly found in?

Answer 16

Muscle cells or sites of high ATP utilisation

Question 17

Describe the structure of peroxisomes

Answer 17

• single membrane
• crystalline structure
• catalase enzymes present
• contains no DNA or ribosomes
• ~0.2-1um in diameter

Question 18

Where are mitochondrial proteins encoded for?

Answer 18

In the nucleus

Question 19

What symptoms do patients suffering with Beriberi display?

Answer 19

• Pain in limbs
• Muscular weakness
• Distorted skin sensation
• Enlarged heart

Question 20

What are the precursors of peroxisomes?

Answer 20

The endoplasmic reticulum

Question 21

What does mtDNA encode?

Answer 21

mtDNA contains 16,569 bp encoding for

• 2 rRNAs
• 22 tRNAs
• 50 proteins

Question 22

Why does a thymine deficiency cause disease?

Answer 22

Thiamine is a prosthetic group for enzymes involved in citric acid cycle
Deficiency causes higher serum levels of substrates below
1. pyruvate dehydrogenase
2. α-ketogluterate dehydrogenase

Question 23

What are the functions of peroxisomes?

Answer 23

• cholesterol and phospholipid production
• Hydrogen peroxide production and catalysis to H2O
• Excess AMP & GMP purines hydrolysed to Uric acid
• Fatty acid oxidation

Question 24

How are mitochondria thought to have come about?

Answer 24

Through the process of endosymbiosis