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basics > Transport of very large particles – endocytosis. Transport through cellular sheets. > Flashcards

Transport of very large particles – endocytosis. Transport through cellular sheets. Flashcards

1
Q

types of endocytosis

A

phagocytosis
pinocytosis
receptor-mediated endocytosis

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2
Q

endocytosis - definition

A

cellular process

to internalise substances from external environment into internal environment

active process - required ATP

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3
Q

phagocytosis points

A

definiton
mechanism
factors
functions

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4
Q

phagocytosis - definition

A

bulk transport of solid media into the cell membrane
via vesicular transport

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5
Q

phagocytosis - mechanism

step 1

A

1) binding
- cell membrane receptors bind onto transported particle
- due to presence of specific antibodies/ complementary proteins on surface

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6
Q

phagocytosis - mechanism

step 2

A

2) engulfing
- cell membrane invaginates this particle by wrapping around it
- due to presence of actin filaments which extend their pseudopodia out

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7
Q

phagocytosis - mechanism

step 3

A

phagosome

  • cell membrane pinches off particle leaving behind a phagosome
  • phagosome = vesicle with particle inside
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8
Q

phagocytosis - mechanism

step 4

A

phagolysosome formation

  • phagosome+ lysosome = phagolysosome
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9
Q

phagocytosis - mechanism

step 5

A

phagolyososome action

  • recyling
  • excretion
  • degradation
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10
Q

phagocytosis - factor 1

A

oppsonisation
- if the particle is coated with an opsonin (antibody) it increases the chances of being recognised by the cell membrane receptors

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11
Q

phagocytosis - factor 2

A

cytokines
- if cytokines are present it increases cellular activity thus phagocytic activity

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12
Q

phagocytosis - factor 3

A

pathogen
- if pathogen is present it will bind to cell membrane receptor instead of particle so no phagocytosis

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13
Q

phagocytosis - function 1

A

immunity

  • phagocytes are primary mechanism for innate immunity
  • phagocytes like neutrophils/ macrophages/ dendrites responsible to phagocytise pathogens
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14
Q

phagocytosis - function 2

A

homeostasis

phagocytes involved in removal of dead cellular debris

example - blood clotting cascade, phagocytes releases cytokines / growth factors

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15
Q

phagocytosis - function 3

A

antigen presentation

involved in antigen presentation on surface

to promote
- MHC
- T-cell activation
- adaptive immunity

example - dendrites/ macrophages

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16
Q

pinocytosis - points

A

definition
mechanism
types
functions

17
Q

pinocytosis - definition

A

bulk transport of liquid droplets into cell membrane via vesicular transport

18
Q

pinocytosis - mechanism

step 1

A

1 - binding
cell membrane receptors bind to transported molecule (liquid droplet)

19
Q

pinocytosis - mechanism

step 2

A

2 - engulfing
cell membrane engulfs transported molecule (liquid droplet)

20
Q

pinocytosis - mechanism

step 3

A

3 - pinocyte formation
cell membrane pinches off particle leaving behind a pinocyte containing ingested fluid + solutes

21
Q

pinocytosis - mechanism

step 4

A

4 - pinocyte action

endosome fusion - contents sorted/ processes
lysosome fusion - contents recycled by hydrolytic digestive enzyme

22
Q

pinocytosis - types

A

micropinocytosis - small liquid droplets

macropinocytosis - large liquid droplets

23
Q

pinocytosis - function 1

A

cell signalling

pinocytes regulate internal cell - ligands/ receptors
pinocytes regulate external cell - hormones/ neurotransmitters

24
Q

pinocytosis - function 2

A

hormone regulation

pinocytes are required by endocrine cells to internalise the hormones released inside bloodstream

25
Q

pinocytosis - function 3

A

plasamembrane turnover

pinocytes involved in
- recycling plasamembrane components
- to maintain cell membrane integrity

26
Q

receptor-mediated endocytosis points

A

definition
mechanism
types

27
Q

receptor-mediated endocytosis - definition

A
  • highly specific transport
  • due to presence of specific receptors on cell membrane surface
28
Q

receptor-mediated endocytosis - mechanism

step 1

A

1 - binding

cell membrane receptors bind to transported molecule (hormones, growth factors, lipoproteins, transferrin)

29
Q

receptor-mediated endocytosis - mechanism

step 2

A

2 - engulfing

cell membrane receptor + ligand = receptor-ligand complex

this triggers formation of clathrin coated pits

to help invaginate the complex

30
Q

receptor-mediated endocytosis - mechanism

step 3

A

3 - endocyte formation

cell membrane pinches off transported molecule, leaving behind an endocyte vesicle

31
Q

receptor-mediated endocytosis - mechanism

step 4

A

4 - endocyte action

fuses with endosomal compartments

complex is sorted/ recycled/ excreted

32
Q

receptor-mediated endocytosis - type 1

A

clathrin-mediated endocytosis

  • formation of clathrin protein pits which help invaginate ligand
  • example LDL
33
Q

receptor-mediated endocytosis - type 2

A

caveolae mediated endocytosis

  • formation of caveolae pits which help invaginate ligand
  • example fibroblast
34
Q

paracellular transport definition

A

movement of substances between adjacent cells
via intercellular junctions

intercellular junctions include:

gap junctions - for direct communication

tight junctions - formed by proteins like claudins/ occlaudins

adherence junctions - for mechanical stability

35
Q

paracellular transport - example

A

blood brain barrier

function - prevent harmful substances from the blood entering the ECM of the brain

location - endothelial capillary cells of brain

importance - prevent toxins entering/ ensure nutrients entering

36
Q

transcellular transport - definition

A

movement of substances across apical AND basolateral parts of cell

via:
- active
- passive
- vesicular

37
Q

transcellular transport - example

A

calcium

function - absorb calcium from food

location - small intestine duodenum
apical = TRPV6 ca2+ channels
basolateral = ca2+-ATPase

importance - maintain calcium levels for bone strength/ muscle function/ blood clotting

basics (9 decks)

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