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medical science xy1110 > cell biology 4 > Flashcards

cell biology 4 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

what is the function of peroxisomes

A
  • perform oxidation reactions using oxygen and peroxide
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2
Q

what is the function of catalase

A
  • converts peroxide to water and oxygen
  • peroxidation of substrate
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3
Q

what is urate oxidases function

A
  • uses oxygen
  • breaks down toxic uric acid
  • produces peroxide and allantoin
  • allantoin cleared by kidneys
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4
Q

what are plasmalogens

A
  • class of phospholipid
  • most abundant in myelin 80-90%
  • originate in the peroxisome
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5
Q

what is the function of plasmalogens

A

antioxidant - protects the cell
- affect fluidity, thickness and lateral pressure

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6
Q

what diseases are linked to peroxisome dysfunction

A
  • alzheimers
  • parkinsons
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7
Q

how are peroxisomes formed from the ER

A
  • various membrane peroxisomal targeting sequences
  • PEX13/16 aid membrane protein insertion
  • vesicles transport to form peroxisomes
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8
Q

how are peroxisomes made in the cytosol

A
  • targeting signals - PTS1(c-terminal and recognised by PEX5) and PTS2 (n-terminal)
  • imported proteins can be folded or in complexes
  • import requires PEX1/6 and ATPase with ATP
  • PEX5 is ubiquitlyation recycles PEX5 in cytosol
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9
Q

what causes zellwegar spectrum disorder

A
  • autosomal recessive
  • defects in peroxisomal targeting —> peroxisome deficiency
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10
Q

what are the symptoms and treatment of zellwegar spectrum disorder

A
  • Varies in severity (Mutation/gene)
  • Abnormalities in brain, liver, and kidneys
  • High mortality
  • Cranial abnormalities, vision problems, hearing loss

Treatment
- None, treat symptoms.

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11
Q

what are the functions of primary lysosomes

A
  • break down intra- and extra- cellular debris
  • use acid hydrolases
  • maintain internal pH 4.5-5
  • found in all eukaryotic cells
  • diverse in shape and size
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12
Q

what is a secondary lysosome

A
  • primary lysosome fused with another cellular compartment
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13
Q

what is an endolysosome

A

primary lysosome fused with late endosome

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14
Q

what is the early endosome

A

fused endocytic vesicles, tubular projections, recycle material to surface

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15
Q

what are recycling endosomes

A

recycle material to surface, can store proteins unit they are needed

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16
Q

what are multivesicular bodies

A

formed by early endosome, self investigation, requires ESCRT protein complex

17
Q

what is the late endosome

A

no tubular projections, fuse with lysosomes/ MVP

18
Q

what are the functions of the nucleus

A
  • genetic storage
  • DNA replication
  • transcription
  • compartmentalisation/ genetic regulation
  • RNA processing
  • ribosome assembly
19
Q

what is heterochromatin

A

dense, inactive DNA

20
Q

what is the function of the nucleolus

A
  • rRNA and tRNA production
  • RNA modification/ processing
  • ribosome subunit assembly
21
Q

what are the characteristics of aqueous passages in nuclear pores

A
  • small molecules can diffuse passively
  • 1000 macromolecules per second
  • bidirectional flow
  • > 60000 daltons cannot enter passively
  • maintains different protein compositions
  • specific transport mechanism used
22
Q

how many nuclear pores per nuclei

A

3000

23
Q

what does nuclear pore complex consist of

A

100s of proteins - 30 different types of nucleoporins

24
Q

what do disordered pore regions do in NPCs

A
  • restrict movement of large molecules
  • phenylalanine-glycine (FG) - repeats of disordered pore regions
25
Q

what are nuclear localisation signs and what do they do

A

1-2 short surface sequences
rich in lysine/arginine
whole complexes can be transported

26
Q

what are nuclear import receptors and what do they do

A
  • soluble cytosolic proteins
  • recognise NLSs
  • family of proteins - different type —> different cargo/signal
  • work together with adaptor proteins
  • binds to phenylalanine-glycine repeats in the disordered region of channel nucleoporins
27
Q

where is the nuclear lamin

A
  • nucleoplasm side of the inner nuclear membrane
  • made from intermediate filament proteins
  • anchored to pore complexes and transmembrane proteins
28
Q

what is the function of nuclear lamin

A
  • provide shape and stability
  • interacts with chromatin at the membrane
28
Q

what happens to nuclear lamin during mitosis

A
  • NPCs and nuclear lamina disassemble to nuclear envelope fragments
  • caused by direct phosphorylation of nucleoporins and lamins by the cyclin-dependent protein kinase
  • pore complex reassemble
29
Q

what happens to ran proteins during mitosis

A
  • Ran-GEF remains bound to chromatin
  • ran proteins close to chromatin mainly GTP bound

medical science xy1110 (40 decks)

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