Membrane

Question 1

What type of molecule are found in lipid rafts?

Answer 1

Glycosphingolipids and cholesterol

Question 2

Three types of lipid rafts

Answer 2

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

Question 3

Lipids in Outer Layer of Membrane

Answer 3

Sphngomyelin and Phosphatidylcholine

Question 4

Lipids in Inner Layer of Membrane

Answer 4

Phosphatidyl Serin, phosphoinositol and phosphatidyl-ethanol

Question 5

Primary compound of membrane

Answer 5

Phospholipid

Question 6

What buffers the fluidity of the membrane?

Answer 6

Cholesterol

Question 7

Describe Peripheral proteins

Answer 7

cytoskeletal proteins: determine shape and stabilize mebrane

Question 8

Name the two types of integral proteins

Answer 8

transmembrane and lipid anchored

Question 9

Describe lipid anchored proteins

Answer 9

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

Question 10

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

Answer 10

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

Question 11

Fxn of CHs in membrane

Answer 11

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

Question 12

What are the two major ways to look at membranes?

Answer 12

Thin Sections and Freeze fracture replicas in EM

Question 13

How are membranes seen in thin layers?

Answer 13

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

Question 14

How are membranes seen in freeze fracture?

Answer 14

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

Question 15

What are IMPs?

Answer 15

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

Question 16

What are the main types of endocytosis?

Answer 16

Pinocytosis, receptor mediated endocytosis, and phagocytosis

Question 17

Describe Pinocytosis

Answer 17

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

Question 18

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

Answer 18

GTPase (dynamin)

Question 19

What protein or lipid raft can participate in pinocytosis?

Answer 19

Caveolin

Question 20

Describe the steps in receptor mediated endocytosis

Answer 20

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

Question 21

What happens in receptor mediated endocytosis when clathrin is released?

Answer 21

Vesicle fuses with early endosomal compartment

Question 22

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

Answer 22

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

Question 23

After receptor has binded the LDL, what happens?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

What results when LDL endocytosis does not function properly?

Answer 25

Familial hypercholesterolemia

Question 26

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

Answer 26

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

Question 27

How do clathrin vesicles attach to early endosomes?

Answer 27

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

Question 28

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

Answer 28

fusion proteins NSF and SNAPs to allow membrane fusion

Question 29

What are the two vesicles that form in phagocytosis?

Answer 29

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

Question 30

What is phagocytosis and are the receptors specific?

Answer 30

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

Question 31

Describe Constitutive Secretion

Answer 31

move continuosly from trans golgi to membrane without storage in cytoplasm

Question 32

Describe Regulated Secretion

Answer 32

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

Question 33

How is the chikungunya Virus inserted to cells?

Answer 33

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

Question 34

How can you remove peripheral proteins?

Answer 34

with high ionic strength solutions