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Biomedical Science FLC > Mitochondria and peroxisomes > Flashcards

Mitochondria and peroxisomes Flashcards

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1
Q

Name 3 diseases mitochondria can be linked to

A

Cancer, cardiovascular disease, dementia

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2
Q

What does the endosymbiotic theory suggest?

A

All existing mitochondria can be traced back to one original prokaryotic cell. The prokaryotic cell was then engulfed by a primitive form of a eukaryotic cell. They formed a symbiotic relationship. The prokaryote divided inside its host, producing daughter cells for when the host cell divided.

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3
Q

Describe and explain the evidence for endosymbiotic theory

A

From phylogenetics

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4
Q

Name the membrane and membrane related structures of the mitochondria

A

Double membrane - Inner, outer
Between - Inter membrane space
Within inner membrane - Mitochondrial Matrix, where metabolic reactions occur

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5
Q

Where are the protein complexes responsible for oxidative phosphorylation

A

Inner membrane

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6
Q

What is the evidence that mitochondria exists from a prokaryotic ancestor

A

Presence of two membranes, presence of small circular genome (own DNA)

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7
Q

Name the other parts of the architecture of the mitochondria

A

ATP synthase particles
Cristae
Ribosome
Granules

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8
Q

How are mitochondria organised in skin fibroblast cells?

A

Interconnected, forming dynamic networks, mitochondria constantly moving in cell.

Individual mitochondria can separate, divide and fuse (fission/fusion)

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9
Q

How are mitochondria organised in cardiac cells

A

Highly abundant in distinct zones. Subcellular populations perform zonal specific functions

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10
Q

How do mitochondria move

A

Requires motor proteins dynein and kinesin, mitochondria must bind to them

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11
Q

What two adapter proteins does mitochondria have on its surface and what do they do

A

Milton and Miro - Bind to kinesin and dynein

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12
Q

Why is transport of mitochondria in neuronal axons for example important

A

Required for neuronal signalling and function in synapses

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13
Q

How are new mitochondria made

A

Grow the mass of existing mitochondria, which then undergo fission to produce new mitochondria.

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14
Q

What happens when as a result of time macromolecules such as DNA in mitochondria are damaged

A

Mitochondria undergo mitophagy to restore overall cellular health.

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15
Q

Name some functions briefly of the mitochondria

A
  1. ATP synthesis (oxidative phosphorylation)
  2. Central hubs of metabolism, not just energy metabolism (Anabolic synthesis of nucleotides for example, used in DNA replication)
  3. As a result of 2, mitochondria can be used in cancer therapy
  4. Calcium homeostasis for muscle contraction
  5. Production of amino acids e.g. glutamate, neurotransmitters.
    6.Apoptosis - Mechanism of cell death/suicide
  6. Immune respones - protein receptors detect viral RNA molecules, located on outer membrane of mitochondria. Activates innate immune response.
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16
Q

Name some functions briefly of the mitochondria

A
  1. ATP synthesis (oxidative phosphorylation)
  2. Central hubs of metabolism, not just energy metabolism (Anabolic synthesis of nucleotides for example, used in DNA replication)
  3. As a result of 2, mitochondria can be used in cancer therapy
  4. Calcium homeostasis for muscle contraction
  5. Production of amino acids e.g. glutamate, neurotransmitters.
    6.Apoptosis - Mechanism of cell death/suicide
  6. Immune response - protein receptors detect viral RNA molecules, located on outer membrane of mitochondria. Activates innate immune response.
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17
Q

What is the citric acid cycle

A

Final common pathway for oxidation of fuel molecules (carbohydrates, fatty acids and amino acids)

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18
Q

What happens to acetyl-coenzyme A in the citric acid cycle

A

Completely oxidised to carbon dioxide

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19
Q

Name the important functions of the citric acid cycle

A

Produce electron donors - NADH and FADH2

Which are then used to synthesise ATP in oxidative phosphorylation

(Catabolic state - breaking into smaller molecules)

  1. To provide biosynthetic precursors for the biosynthesis of fatty and amino acids (Anabolic state - synthesising bigger molecules)
20
Q

Describe first reaction of the citric acid cycle

A

Acetyl-CoA (2C) combines with oxaloacetate (4C) to make citrate (6C), catalysed by citrate synthase

21
Q

What happens to citrate after it is formed in the citric cycle

A

Citrate isomerised into first cis-aconitase then isocitrate, catalysed by aconitase

22
Q

What happens to isocitrate in the citric cycle

A

Isocitrate (6C) oxidised into alpha-ketoglutarate (5C) catalysed by isocitrate dehydrogenase

One molecule of NAD reduced to NADH, and one molecule of CO2 produced.

23
Q

What happens to alpha-ketoglutarate

A

Converted into succinyl-CoA (4C) by alpha ketoglutarate dehydrogenase. NAD reduced to NADH, CO2 produced

24
Q

What happens to succinyl-coenzymeA

A

Converted to succinate by succinyl coenzyme A synthetase, GTP molecule produced

25
Q

What happens to succinate

A

Converted to fumarate by succinate dehydrogenase, a molecule of FADH2 is produced

26
Q

Where is the succinate dehydrogenase found, why is this different

A

Inner membrane of mitochondria. The other citric acid cycle enzymes are soluble enzymes in the mitochondrial matrix

27
Q

What happens to fumarate

A

Converted to malate by catalyst fumarase

28
Q

What happens to malate

A

Converted to oxaloacetate (4C) through malate dehydrogenase, and 1 NADH formed.

29
Q

What are the overall products of the citric cycle

A

3xNADH
1xFADH2
2xCO2
1xGTP

30
Q

What are the NADH and FADH2 used in

A

Electron transport chain to produce ATP.

31
Q

What two steps make up oxidative phosphorylation

A
  1. Generation of a proton motive force (ETC/Respiratory chain)
  2. Chemiosmosis (ATP synthase)
32
Q

Which membrane embedded protein complexes are involved in oxidative phosphorylation

A

NADH dehydrogenase
Succinate dehydrogenase
Cytochrome-BT1 complex
Cytochrome-C oxidase
ATP synthase

(number I-V)

Proteins 1-4 are involved in transfer of electrons and generation of motive force. They are part of the ETC. Respiratory chain complexes.

33
Q

What do ubiquinone and cytochrome C do in oxidative phosphorylation

A

Small electron carriers

34
Q

How is NADH used in oxidative phosphorylation

A

Electrons from NADH enter at complex I. NADH -> NADP+

Complex I becomes charged, protons transported from matrix side to inter membrane space. A transmembrane potential is generated, the intermembrane space becomes positive to the matrix’s negative charge.

35
Q

How is FADH2 used in oxidative phosphorylation

A

Enters ETC at complex II. FADH2 -> FAD
Complex II does not pump protons, does not contribute to motive force.

36
Q

What happens to electrons after they enter complexes I and II

A

Electrons transported to ubiquinone, then to III, then to IV through cytochrome C, both III and IV pump protons and contribute to motive force.

37
Q

What happens in the last step of the electron transport chain

A

At complex IV, the electron is donated to the terminal acceptor oxygen, which is then reduced to water.

38
Q

What happens aftre the electrochemical gradient is formed between the matrix and the intermembrane space (protons/electrons)

A

Protons flow back into the matrix through complex V, harnessing the energy from proton flow to synthesise ATP through the phosphorylation of ADP with Pi.

39
Q

What is the sum of ATP generated from NADH and FADH2

A

2.5 molecules of ATP from NADH
1.5 from FADH2

40
Q

Describe the structure of peroxisomes

A

Single membrane bilayer
Do not have own DNA

41
Q

State main functions of the peroxisome

A

Fatty acids broken down inside peroxisomes through B-oxidation. Breaks down even long chain fatty acids.

Detoxification of the hydrogen peroxide - Reactive oxygen species which can damage macromolecules e.g. DNA, protein, which could cause cellular dysfunction and contribute to ageing.

42
Q

State some other functions of peroxisomes

A

Metabolism of bile acids, important in digestion and synthesis of cholesterol

43
Q

What is the enzyme that detoxifies hydrogen peroxide called

A

Catalase

44
Q

How do peroxisomes replicate

A

Peroxisomal fission

45
Q

State proteins involved in peroxisomal and mitochondrial fission

A

DNM1L, FIS1

46
Q

State some shared features of mitochondria and peroxisomes

A

Important in cellular metabolism (fatty acids)
Can divide
Proteins required for division on outside of both organelles
Anti-viral signalling (MAVs complex present on both outer membranes)

47
Q

Why are mitochondrial diseases complex

A

Some are caused by mutations in mitochondrial DNA, which affect oxidative phosphorylation.

Biomedical Science FLC (10 decks)

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