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C Bio > Vesicular Targeting, Lysosomes & Endosomes (15) > Flashcards

Vesicular Targeting, Lysosomes & Endosomes (15) Flashcards

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1
Q

what facilitates movement of vesicles?

A

microtubules & motor PROs

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2
Q

when does the vesicle attach to motor PROs?

A

when the coat is shed, there is a PRO on the vesicle enabling motor PRO attachment

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3
Q

Rab PRO

A

integral membrane PRO

GTP binding PRO

direct vesicles to where they need to go in the cell & then tethering PROs attach to Rabs bringing them closer to the target membrane

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4
Q

T-SNARE

A

located on the receiving/target membrane (diff ones on diff target membranes)

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5
Q

V-SNARE

A

located on the vesicle, type of V-SNARE is determined by the type of COP PRO on the vesicle

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6
Q

SNARE PROs

A

family of diff PROs each with a diff location/target

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7
Q

when are V-SNAREs incorporated in the vesicle?

A

incorporated in the membrane during budding

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8
Q

docking

A

T-SNARE on the receiving membrane has an affinity for the V-SNAREon the vesicle

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9
Q

how do vesicles fuse with their target membranes?

A

SNARE PROs intertwine & pull membranes together allowing them to fuse

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10
Q

nerve cells membrane fusion

A

nerve cells releasing neurotransmitters synaptic vesicle dock to presynaptic membrane in nerve cells

vesicles are dumped & fuse with postsynaptic membrane (neuron, muscle etc.)

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11
Q

what happens to SNARES once the vesicle has fused?

A

recycled through interactions with COP I

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12
Q

when do V & T SNARES interact?

A

during tethering

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13
Q

what do lysosomes breakdown?

A 
organic substances: 
	NAs
	PROs
	GAGs (glycosaminoglycans) 
	Glycogen
	Oligosaccharides 
	Sphingolipids 
	Phospholipids 
	Triglycerides
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14
Q

what happens to the compounds that lysosomes breakdown?

A

various transporters dump subunits into the cytoplasm to be reused

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15
Q

PROs (enzymes) destined for the lysosome are tagged with ____

A

phosphorylated mannose (6) residues

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16
Q

what is the role of clathrin?

A

Coat PRO, clathrin facilitates the vesicles budding from the Golgi which then travel to a phagosome or other vesicle, clathrin will shed facilitating fusion (primary lysosome)

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17
Q

primary lysosome

A

Non-functional lysosome, enzymes haven’t been activated

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18
Q

secondary lysosome

A

enzymes are activated & are capable of hydrolysis

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19
Q

what does the lysosomal membrane contain?

A

Proton pump maintaining the pH inside by pumping protons inside

2 groups of acidic, highly glycosylated PROs line the interior protecting the inner lining from the enclosed enzymes

20
Q

When do lysosomal enzymes have optimal activity?

A

at an acidic pH

21
Q

heterophagy

A

degradation of foreign material brought into the cell by phagocytosis

Primary lysosome fuses with the phagosome & digests the contents

Introduce the enzymes converting it into a secondary lysosome

22
Q

what are purposes of heterophagy?

A

nutrition: products move into the cytoplasm
defense: microorganisms are killed

23
Q

what type of cell acts as a defense mechanism in heterophagy?

A

white blood cells destroying microbes

24
Q

phagolysosome

A

lysosome + phagosome

25
Q

autophagy

A

digestion of intracellular components that have damage or no longer needed

Isolation envelope forms around components, fuses with primary lysosome, dump enzymes, lower the pH & contents are degraded

26
Q

autophagolysosome

A

lysosome + autophagic vacuole

27
Q

autolysis

A

rupture of lysosome within cytoplasm kills the cell

28
Q

when does autolysis occur?

A

when infection cannot be resolved

programmed cell death during development, ex: selective removal of cells removing webbing b/w fingers & toes

29
Q

extracellular digestion

A

lysosomes may discharge their enzymes to the outside of a cell by exocytosis

30
Q

when does extracellular digestion occur?

A

acrosome in sperm fertilization

sperm will hit the egg, release lyssomes with digestive enzymes allowing the sperm to enter the egg & fuse with the membrane& fertilize

31
Q

how do phagocytosed bacteria escape destruction?

A

Fusion of primary & phagosome is inhibited

Bacterium prevent proton pumps from working, pH is not where it needs to be & enzymes are unable to perform their function

Bacteria escape secondary lysosome by producing phospholipase to destroy lysosomal membrane (lysosome bursts and bacteria move out)

32
Q

What are ways that lysosomes fail to carry out their functions?

A

Phagocytosed bacteria escape

Lysosome with a missing acid hydrolase

33
Q

what occurs in lysosomes with a missing acid hydrolase?

A

Lysosomes don’t have necessary enzymes to break down the materials so they accumulate

34
Q

endocytosis

A

cellular uptake of particles & macromolecules

35
Q

what are the types of endocytosis?

A

Phagocytosis: uptake of particulate matter

Bulk phase (pinocytosis): cell drinking, uptake of extracellular fluids without recognition by surface of PM 
	Brings anything in that’s around the area where endocytosis occurs

Receptor-mediated endocytosis: uptake of specific macromolecules
Brought to endosomes

36
Q

what are professional phagocytes in phagocytosis?

A

macrophages

neutrophils

37
Q

how do lysosomes kill ingested microbes?

A

Contain lysozyme, an enzyme that degrades bacterial cell walls

Acidic pH kills some bacteria alone

Oxidases on inner surface of phagosome produce hydrogen peroxide that kills some bacteria

38
Q

what type of endocytosis has coat PROs?

A

receptor-mediated

39
Q

early endosomes

A

located near the periphery of the cell, aggregation of endocytotic vesicles

40
Q

late endosome

A

interior of the cell, sort materials & send them off to fuse with a primary lysosome (activating the secondary lysosome

41
Q

where do late endosomes receive material from?

A

Receive materials from: early endosomes & Golgi

42
Q

what type of endosome can develope into lysosomes?

A

late endosome

43
Q

coated pits

A

sites on membrane where receptors for receptor-mediated endocytosis are concentrated

coated with clathrin PRO (on the cytoplasmic side)

44
Q

what are the steps in the endocytosis pathway?

A
  1. Clathrin coat is removed from coated vesicle to yield uncoated vesicle
    Strips receptors & sending them back to be recycled
  2. Uncoated vesicle fuses with early endosome
  3. Transport or carrier vesicle buds off from early endosome
  4. Transport vesicle fuses with late endosome
  5. Transport vesicle bud off from late endosome & contain either:
    a. Ligand only
    b. Receptor only
    c. Receptor ligand complex
45
Q

How do endosomes deal with receptors & ligands? (4)

A

Receptor returned to PM & ligand delivered to lysosome for degradation
Nutrition

Both receptor & ligand returned to PM where ligand is released

Both receptor & ligand are destroyed in a lysosome

Receptor & ligand delivered to opp side of cell & ligand released into extracellular space
Transcytosis

46
Q

Transcytosis

A

where receptor & ligand are taken in from one side & sent out the other

47
Q

when does transcytosis occur in humans?

A

Infant’s intestines take up antibodies from mom’s milk. The infant takes the antibodies in with receptors & prevents digestion by sending them out the other side

C Bio (30 decks)

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