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Cytology > Vesicle trafficking > Flashcards

Vesicle trafficking Flashcards

1
Q

Vesicular trafficking def

A

the process by which vesicles transport mateirlas between diff, cellular compartments/ between cell and environment

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2
Q

compare and contrast endo and exocytosis

A

ENDO: nutrient uptake/cell signaling/change in cell shape/ controls cell response to external environment

EXO: release of cargo molecules

!! BOTH: control the composition of the plasma membrane

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3
Q

2 types of exocytosis and mechanisms

A
  1. CONSTITUITIVE:
    -COP coated vesicles
    -not dependent on specific stimulation
    -continuous process (products are immediately secreted so there is no accummulation of vesicles)
    -USED BY: plasma cells for immunoglobulins and fibroblasts for procollagen
  2. REGULATED:
    -cathrin coated vesicles
    -control of specific stimulation (Ca2+ transient flux)
    -stimulates the fusion of vesicles with plasma membrane
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4
Q

embedding def

A

vesicle originates from a cell compartment and it travels to a diff cell compartment (eg. vesicles from ER go to Golgi)

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5
Q

3 types of endocytosis

A
  1. receptor mediated
  2. phagocytosis
  3. pinocytosis
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6
Q

components needed for endocytosis

A
  1. ATP
  2. Ca2+
  3. cytoskeletal elements for motility (microfilaments)
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7
Q

2 types of phagocytosis

A

DIRECT: recognition of oligossacharides on pathogen surface

INDIRECT: recognition of antibodies on pathogen surface

!! both are receptor mediated

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8
Q

process of phagocytosis (3 steps)

A
  1. recognition of particle to be ingested
  2. formation of pseudopods (polymerisation of actin)
  3. internailsation of the particle forming a phagosome

!! then combines with lysosomes to hydrolyse

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9
Q

disorders stemming from phagocytosis malfunction

A

GENETIC DISORDERS:
1. neutrophill differentiation malfunctions

  1. motility malfunctions
  2. specific enzyme malfunctions which alters the ability to digest the particle
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10
Q

pinocytosis definition and 2 types

A

DEF: non specific introduction of small liquid droplets from environment into cell

  1. MACRO:
    -clathrin independent, actin dependent
    -for nutrients and antigens
    -regulated by GFs
  2. MICRO:
    -clathrin AND actin independent
    -for fluids and small moclecules
    -involves calveolin and flotilin proteins
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11
Q

receptor mediated endocytosis (6 steps)

A
  1. cargo binds to receptor and is coated with clathrin
  2. binding changes conformation of receptor - causes interaction with adaptin protein
  3. adaptin favors connection between cargo/clathrin
  4. invagiation of membrane forming the coated pit and then vesicle
  5. dynamin protein forms spiral on the base of vesicle and closes the vesicle up –> dettachment into cytoplasm
  6. dettachment of clathrin and recycling back into membrane to be reused
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12
Q

endosomes def

A

membrane bound vesicles associated with the endocytic pathway

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13
Q

2 hypothesis for biogenesis of endosomes

A
  1. STABLE COMPARTMENT MODEL: stable compartment connected through vesicle with extracellular environment and golgi fusion due to specific receptors
  2. MATURATION MODEL: formed denovo by endocytic vesicle origniating from plasma membrane (removal of specific receptors)
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14
Q

types of endosomes

A
  1. early: ph 6.5, located near plasma membrane, lumen is divided into cisternae
  2. late: ph 5.5, located deeper in cytoplasm (near golgi/nuc), ph drop is due to membrane pumps for H+ intake
  3. lysosome: most mature, ph 5, contains lytic enzymes
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15
Q

what is necessary for the maturation from the late stage endosome to lysosome

A

-newly synthesised lysosomal enzymes
-synthesis of proteins needed:

SOLUBLE PROTEINS: addition of mannose 6 phosphate residues

MEMBRANE PROTEINS: short cytoplasmic C terminus domain recognised by adaptin and secrete clathrin coated veicles

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16
Q

function of lysosomes

A

main site of cellular digestion, destroy microorganisms or damaged cells

17
Q

structure of lysosomes

A

-heterogenous/variable morphology and shape
-contain acid hydrolases
-ph5
-H+ membrane pumps
-membrane glycoproteins that protect inner surface from the internal lytic enzymes

18
Q

4 models of lysosome biogenesis

A
  1. maturation (from early and late endosomes)
  2. vesicular transport
  3. kiss and run: late endosome contact site with lysosome and transfer of cargo
  4. fusion/fission: forms hybrid organelle followed by lysosome reformation
19
Q

visualisation of lysosomes

A

-use of tracker to mark one of its components
-staining cells embedded in paraffin with histological dyes (toludeine blue)
-fluorescent microscopy

20
Q

exceptions to normal behaviour of lysosome secretion

A

NORMAL: they would only release enzymes within the space of the organelle itself

EXCEPTIONS: contents are released out of the cell
1. SPERM: acrosome released for destruction of zona pellucida
2. OSTEOCLASTS: bone resorption
3. PHAGOCYTOSIS: release within phagolysosome

21
Q

primary secondary and tertiary lysosome

A

PRIMARY: sacs with enzymes, without substrate

SECONDARY: larger, formed by fusion of the primary lysosome with the phagosome

TERTIARY: contain residues of material that can no longer be broken down, such as lipofuscin.

22
Q

example of n undigested body

A

LIPOFUSCIN: remains inside cell (especially neurons)

23
Q

lysosomal storage sisorders

A

-usually genetic
-there is absence of one or more proteins and enzymes
-undigested material/residual bodies accummuate in cells

24
Q

process of autophagy and 3 types

A

DEF: self destruction of cells by internalising ‘damaging’ cytoplasmic components into the lysosomes

  1. MACRO: cytoplasmic portion is surrounded by double membrane to form autophagosome. This then fuses with lysosome for digestion
  2. MICRO: cytoplasmic proteins internalised into lysosomes by invagination of lysosomal membrane
  3. CHAPERONE MEDIATED: chaperone mediates transport into lysosome lumen (MOST SELECTIVE PROCESS)
25
Q

transcytosis def

A

used for transport of substances from one end of the cell to the other –> receptor mediated

26
Q

Types of protein coats a vesicle can have (3)

A
  1. clathrin –> vesicles undergoing endocytosis
  2. COP1 –> movement from Golgi to RER (retrograde)
  3. COP2 –> movement from RER to Golgi (anterograde)
27
Q

purpose of vesicle coating (2)

A
  1. favours bending of the membrane to form vesicles
  2. influences selection of cargo components to be inserted and transported into vesicle
28
Q

Structure of the clathrin

A

-hexameric protein (3 light and 3 heavy chains)
-arranged in 3 arm TRISKELION
-surrounds vesicles

29
Q

how are transport vesicles directed to SPECIFIC target organs?

A

v-SNARE on vesicles bind to t-SNARE transmembrane proteins on target organelle.

!! link and interaction between the two forms the fusion complex

Cytology (8 decks)

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