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From Flashcardlet > Microanatomy: Peroxisomes and Mitochondria > Flashcards

Microanatomy: Peroxisomes and Mitochondria Flashcards

1
Q

Peroxisome (6)

A
  • Small, spherical organelle responsible for producing and breaking down hydrogen peroxide
  • Also have roles in
    - Breakdown of fatty acids
    - Detoxification
    - Synthesis of cholesterol, bile acids, and myelin
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2
Q

Structure of peroxisomes (4)

A
  • Small, spherical
  • Surrounded by single lipid bilayer
  • Granular matrix due to presence of numerous enzymes
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3
Q

Functions of peroxisomes (12)

A
  • Breaks down phytanic acid by alpha oxidation
  • Breaks down long chain fatty acids by beta-oxidation, which produces H2O2
  • Catalase degrades H2O2, yielding water and oxygen
  • Detoxification
  • Biosynthesis of myelin precursor, bile acids, and cholesterol
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4
Q

Peroxisomes have no ____. Therefore, all peroxisomal proteins are encoded by the ___, made in the ___, and then transported into ___ by ____

A
  • Have no endogenous DNA
  • All peroxisomal proteins are encoded by cell nucleus, made in cytosol, and then transported into peroxisomes by peroxins
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4
Q

Peroxisomes are most abundant in (2)

A
  • Liver and kidney
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5
Q

Replication and biogenesis of peroxisomes (3)

A
  • Replicate by fission or budding from existing peroxisomes
  • Biogenesis: acquire membranes from ER
  • No endogenous DNA
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6
Q

How are proteins taken up into peroxisomes?

A
  • Protiens with peroxisome targeting signal bind to peroxins and are taken up into peroxisomes
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7
Q

PTS1 (peroxisome targeting signal 1)

A

3 aa sequence at C-terminus

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8
Q

PTS 2 (peroxisome targeting signal 2)

A

Less conserved sequence at N-terminus

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9
Q

Two classes of peroxisomal diseases

A
  • Peroxisome biogenesis disorder

- Single peroxisomal enzyme deficiency

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11
Q

Zellweger Syndrome (2)

A
  • Most severe peroxisome biogenesis disorder

- Caused by mutations in the peroxin genes, so no peroxisomes are formed

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12
Q

X-linked adrenoleukodystrophy (3)

A
  • Most common peroxisomal disorder
  • Caused by single peroxisomal enzyme deficiency
  • Mutation in ABCD1 gene, which encodes ALD protein important for transport of fatty acids into peroxisomes
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13
Q

Adult Refsum Disease (3)

A
  • Type of single peroxisomal enzyme deficiency
  • Rare autosomal recessive disorder
  • Mutation in PHYH gene, important for alpha-oxidation of phytanic acid
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14
Q

All enzymes of the ETC are embedded in the

A

inner membrane

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14
Q

Roles of mitochondria (6)

A
  • Energy production (ATP synthesis)
  • Calcium storage
  • Regulation of programmed-cell death
  • Breakdown of carbohydrate, lipid, and protein derivatives
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15
Q

Outer membrane of mitochondria is permeable to (2)

A
  • Small molecules and ions
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16
Q

Where H+ ions accumulate to create a H+ gradient that can drive ATP synthesis

A
  • Intermembrane space
17
Q

Inner membrane of mitochondria is impermeable to (3)

A

small molecules and ions, including H+

19
Q

Excess cellular calcium is sequestered in

A

Mitochondrial matrix

19
Q

Matrix of mitochondria contains (6)

A
  • Enzymes required for the oxidation of pyruvate and fatty acids and for the TCA
  • Mitochondrial DNA
  • Ribosomes
  • tRNAs
20
Q

Catabolism in the mitochondria (5)

A
  • Oxidizes long-chain fatty acids and pyruvate into acetyl CoA and then oxidizes acetyl CoA via the citric acid cycle
21
Q

Mitochondria replicate by

A

Fission or budding from existing mitochondria

22
Q

Mitochondrial regulation of apoptosis (2)

A
  • Mitochondrial release of cytochrome c and calcium induces apoptosis
23
Q

ETC contains

A

4 enzyme complexes + ATP synthase

24
Q

Protein import in mitochondria (2)

A
  • Proteins with mitochondrial signal peptide (SP) are transported into different compartments within mitochondria
  • Chaperones keep newly translated proteins unfolded so they can cross the membrane
26
Q

NADH dehydrogenase (3)

A
  • Complex I

- Pumps H+ to intermembrane space and e- to ubiquinone

27
Q

Succinate (FADH2) dehydrogenase (4)

A
  • Complex II

- Removes 2H+ from FADH2 and passes e- to ubiquinone

28
Q

Cytochrome c reductase (6)

A
  • Complex III

- Transfers H+ to intermembrane space and e- from ubiquinone to cytochrome c

29
Q

Cytochrome c oxidase (5)

A
  • Complex IV

- Moves H+ to intermembrane space and e- to reduce molecular oxygen to water O2 –> 2 H2O

30
Q

ATP synthase (2)

A

As 3 H+ flow through this channel and back into the matrix, ADP –> ATP

31
Q

Mitochondrial diseases can be (2)

A
  • Autosomal: originating from mutations in mitochondrial proteins encoded by genomic DNA
  • Maternally inherited: due to mtDNA mutations passed from a mother to all her children
32
Q

Heteroplasmy (2)

A
  • A mixture of mutated and normal mitochondria present in a mother’s egg cell redistribute unevenly as the zygote divides, and those tissues that receive more mutated mitochondria show more signs of disease
  • mtDNA replicates and sorts randomly
33
Q

How do peroxisomes replicate (4)

A
  • They replicate by fission or budding from existing peroxisomes and acquire their membranes from the ER.
  • Because they don’t have their own DNA, they acquire proteins from ctyosol and import these proteins
34
Q

Structure of peroxisomes (4)

A
  • One membrane

- Granular matrix with oxidase and catalase

35
Q

Structure of mitochondria (5)

A
  • Double membrane
  • Matrix containing catabolic enzymes
  • Cristae containing ETC enzymes
36
Q

Function of peroxisomes (9)

A
  • alpha and beta oxidation of fatty acids
  • Breakdown of H2O2
  • Detoxification of alcohol and purines
  • Biosynthesis of bile acid, cholesterol, and precursor to myelin
37
Q

Function of mitochondria (4)

A
  • Beta-oxidation of fatty acids
  • ATP synthesis
  • Calcium homeostasis
  • Regulation of programmed cell death
38
Q

Replication and biogenesis of peroxisomes (3)

A
  • Replicate by fission
  • No endogenous DNA
  • Get membranes from the ER
39
Q

Replication and biogenesis of mitochondria (3)

A
  • Replicate by fission
  • Endogenous mtDNA that encodes some mitochondrial genes
  • Maternal inheritance
40
Q

Diseases caused by peroxisome disorders (4)

A
  • Neurological defects due to lack of myelination and accumulation of VLCFA
  • Have spectrum of severity
41
Q

Diseases caused by mitochondrial disorders (3)

A
  • Mitochondrial enzyme deficiencies
  • Abnormal mitochondria
  • Varying degree of severity and involvement of numerous tissues

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