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Cell & Molecular Biology > Transport into mitochondria & peroxisomes > Flashcards

Transport into mitochondria & peroxisomes Flashcards

1
Q

What is the primary function of the mitochondria?

A

Produce H+ gradient across inner membrane, which drives the ATPase, which produces ATP.

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2
Q

What is the first step in the mitochondria producing ATP?

A

Glycolysis - the breakdown of glucose in pyruvate occurs in the cytoplasm.

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3
Q

What happens when the pyruvate enters the mitochondria?

A

Decarboxylation

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4
Q

Describe the 2 membranes in the mitochondria

A

Outer membrane - encloses the organelle.

Inner membrane - highly folded (high SA). These folds are known as cristae.

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5
Q

What does the inner matrix contain?

A

The enzymes responsible for energy production

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6
Q

Why is the outer membrane being perforated (large channels - porins) beneficial?

A

Allows entry of molecules <5000 kDa

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7
Q

What type of enzymes are present in the outer membrane?

A

Enzymes involved in mitochondrial lipid synthesis

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8
Q

What enzymes are present in the inter membrane space?

A

Enzymes that use ATP to phosphorylate other nucleotides

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9
Q

What enzymes are present in the mitochondrial matrix?

A

Enzymes involved in the Krebs cycle

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10
Q

What is contained in the mitochondrial matrix?

A
  • mitochondrial DNA
  • ribosomes
  • tRNAs & rRNAs
  • enzymes
  • metabolites
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11
Q

Describe the mitochondrial genome

A
  • circular chromosome (double-stranded)
  • 15-17 Kbps (kilo base pairs)
  • encodes 37 genes
  • the mitochondrial DNA is inherited from the mother.
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12
Q

Describe the process of how undesirable chemicals produced as a by-product of metabolism in the mitochondria

A

the debris is separated to one side of mitochondria. Fission then occurs, with one half staying healthy. The smaller & damaged mitochondria can then be targeted and an autophagosome is created.

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13
Q

How does mitochondria create more ATP in emergency situation?

A

healthy mitochondria fuses with damaged mitochondria to create more ATP (fussion).

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14
Q

Where are mitochondria synthesized from?

A

new mitochondria must arise from existing mitochondria

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15
Q

How does the cell regulate the level of mitochondria present?

A

Balances the dynamic flux between fission & fusion

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16
Q

What translocation proteins embedded into the mitochondrial membranes are used to transport proteins into mitochondria (which 3 complexes)?

A

TOM - Translocator of the Outer Membrane
TIM - Translocator of the Inner Membrane
SAM - Sorting & Assembly Machinery

17
Q

What complex allows the movement of a protein once it docks on a receptor?

A

TIM23 complex

18
Q

How do the proteins manage to fit into the mitochondria?

A

the proteins UNFOLD before docking with the TOM complex

19
Q

Why are chaperones useful in transporting proteins into the mitochondria?

A

chaperones bind to peptides, as they are made & control how they fold

20
Q

What do chaperones need to dissociate from the polypeptide chain?

A

ATP

21
Q

What is the end result of the electrochemical H+ gradient driven by electron transport?

A

ATP production

22
Q

How do proteins enter the OUTER membrane?

A

through porins (beta-barrel proteins)

23
Q

What is the solution, as TOM cannot insert proteins into bilayer?

A

The proteins are kept unfolded by chaperones.

24
Q

How do you get a soluble protein in the inter membrane space?

A

You cleave after membrane insertion

25
Q

Are there different pathways depending on what is being transported?

A

YES

26
Q

How many membranes are present in peroxisomes?

A

1

27
Q

Are there DNA or ribosomes in peroxisomes?

A

NO

28
Q

Where are peroxisomes?

A

in eukaryotic cells

29
Q

What is the function of peroxisomes?

A

Contains a variety of oxidative enzymes which remove hydrogen atoms from various organic compounds.

30
Q

What is the reaction that peroxisomes use to remove Hydrogen atoms?

A

RH2 + O2 –> R + H2O2

31
Q

What role does the peroxisomes play in the liver?

A
  • detoxification
  • processing of alcohol
  • oxidation of fatty acids (breaking down fat)
32
Q

Where are peroxisomal membrane proteins made?

A

cytoskeleton - then insert into the membrane of pre-existing peroxisomes

33
Q

How are peroxisomes created?

A

peroxisomes arise from pre-existing ones, by organelle growth & fission - like mitochondria

34
Q

How do proteins get into peroxisomes?

A

Peroxins (using ATP) form a trans locator in the membrane. Pex5 recognises signal sequences & accompanies cargo into peroxisomes.

35
Q
A

Cell & Molecular Biology (20 decks)

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