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Histology Exam I > Membrane > Flashcards

Membrane Flashcards

1
Q

What type of molecule are found in lipid rafts?

A

Glycosphingolipids and cholesterol

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2
Q

Three types of lipid rafts

A

Glycosphingolipid-enriched membranes, polyphosphoinositol-rich rafts, and caveolae-flask-shape with protein caveolin

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3
Q

Lipids in Outer Layer of Membrane

A

Sphngomyelin and Phosphatidylcholine

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4
Q

Lipids in Inner Layer of Membrane

A

Phosphatidyl Serin, phosphoinositol and phosphatidyl-ethanol

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5
Q

Primary compound of membrane

A

Phospholipid

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6
Q

What buffers the fluidity of the membrane?

A

Cholesterol

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7
Q

Describe Peripheral proteins

A

cytoskeletal proteins: determine shape and stabilize mebrane

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8
Q

Name the two types of integral proteins

A

transmembrane and lipid anchored

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9
Q

Describe lipid anchored proteins

A

integral proteins that covalently link to lipids but does not through biayer core. Ex: G-proteins

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10
Q

Where in the membrane are CHs found and to what do they bind

A

extracellular surface as cell coat or glycocalyx and bind to lipids or integral proteins

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11
Q

Fxn of CHs in membrane

A

Receptos for hormones and viruses, cell-cell recognition (A,B,O type), and can be related to cancer

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12
Q

What are the two major ways to look at membranes?

A

Thin Sections and Freeze fracture replicas in EM

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13
Q

How are membranes seen in thin layers?

A

trilaminar structure with two dense outer layers and middle translucent. Plasma membrane is thicker than cytoplasmic

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14
Q

How are membranes seen in freeze fracture?

A

split along the central plane of the bilayer producing two fractures: E-face and P-face (has the IMPs

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15
Q

What are IMPs?

A

integral membrane proteins seen mainly in the P face of freeze fracture… number and size correlates with amount and type of proteins expected

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16
Q

What are the main types of endocytosis?

A

Pinocytosis, receptor mediated endocytosis, and phagocytosis

17
Q

Describe Pinocytosis

A

a constitutive, non-specific, endocytosis that is independent of specific receptors and clathrin… carrys small amounts of fluid and proteins

18
Q

What mechanoenzyme is involved in pinching off vesicles in pinocytosis and receptor mediated endocytosis?

A

GTPase (dynamin)

19
Q

What protein or lipid raft can participate in pinocytosis?

A

Caveolin

20
Q

Describe the steps in receptor mediated endocytosis

A
  1. Ligand binds to receptor 2. Apadtins bind to recognition sequences on the cytoplasmic domain of receptor 3. Clathrin molecules bind to clathrin binding sites on adaptin protein 4. Clathrin aggregation provides for to bend membrane and then it pinches off with help of dynamin
21
Q

What happens in receptor mediated endocytosis when clathrin is released?

A

Vesicle fuses with early endosomal compartment

22
Q

What molecules do LDL’s receptor bind to and how?

A

APO B100 by binding to the cholesterol it contains in its amino terminal through charge-charge interactions

23
Q

After receptor has binded the LDL, what happens?

A

Receptor becomes clustered into coated pits through interaction with an adaptin protein, then it is transported into the cell in a clathrin coated vesicle to an early endosome

24
Q

What properties does the adaptin protein participating in LDL endocytosis have?

A

a binding site for the NPxY motif and a clathrin binding consensus box

25
Q

What results when LDL endocytosis does not function properly?

A

Familial hypercholesterolemia

26
Q

What are the possible outcomes in the processing of receptor and ligand in receptor mediated endocytosis?

A
  1. breakdown of ligand and recycling of receptor 2. breakdown of both, recycling of voth, transcellular transport of both
27
Q

How do clathrin vesicles attach to early endosomes?

A

Through SNARE proteins, vesicle is formed with V-SNARE and attaches to T-SNARE in the early endosome to form a CIS-SNARE

28
Q

What molecules are recruited when cis-SNARE forms and why?

A

fusion proteins NSF and SNAPs to allow membrane fusion

29
Q

What are the two vesicles that form in phagocytosis?

A

Phagosome (phagocytosed particle) and phagolysosome (fused with a lysosome)

30
Q

What is phagocytosis and are the receptors specific?

A

the endocytosis of particles larger than 250nm in dimeter… receptors can be either specific or non-specific

31
Q

Describe Constitutive Secretion

A

move continuosly from trans golgi to membrane without storage in cytoplasm

32
Q

Describe Regulated Secretion

A

move from trans golgi to the apical region of the cell where they are stored until secretion is stimulated

33
Q

How is the chikungunya Virus inserted to cells?

A

either through clathrin receptor mediated or non-clathrin receptor mediated endocytosis. It does not require a specific receptor for the virus.

34
Q

How can you remove peripheral proteins?

A

with high ionic strength solutions

Histology Exam I (6 decks)

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