Cell Membrane

Question 1

Describe the Eu Cell coat

Answer 1

Known as glycocalyx and has a tri-laminar appearance. Includes proteins, cholesterol, and glycolipids. 5% of the membrane is made of Carbohydrates. Caner has a different cell coat and can be a target for treatment

Question 2

What is the function of carbohydrates on cell coat

Answer 2

Protection, recognition, adhesion, repulsion

Question 3

Describe carbohydrate cell recognition

Answer 3

1. Oligosaccharide is complex
2. Carbs are primary marker for attachment. Activated endothelial cells bind to oligo an WBC and platlets. L-selectin recog lymph organ endo cells.

Question 4

What are the functions of Cell Membrane

Answer 4

Fluidity, structure, protection, selective permeability, compartmentalization, signal and adhesion. (Mito for biochem scaffolding)

Question 5

Describe Lipids and the 3 classes

Answer 5

Amphipathic (H-philic head and H-phobic tail). 3 classes are phospholipids, Glycolipids, Cholesterol

Question 6

Describe Phospholipids

Answer 6

1 head and 2 tails. Phosphatidylcholine is most common (1 sat and 1 unsat tail). PL’s made in cytoplasm and flipped out

Question 7

Describe glycolipids

Answer 7

On EC leaflet with carb residues forming glycocalyx. Functions in cell-cell recognition, apical protection, nerve conduction.
Gm1 ganglioside = cholerea toxin receptor

Question 8

Describe Cholesterol

Answer 8

On both leaflets, increases stability, fills gaps btwn PL and steroid ring immobilizes surrounding PLs

Question 9

What are the function of CM proteins

Answer 9

Transport, Anchor, Receptors, Enzymes, Cell ID (MHC), gap jx. Bound to actin skeleton and lip:protein ratio determines function

Question 10

What are the 3 classes of proteins

Answer 10

Integral (amphipathic), Peripheral, Lipid-Anchored

Question 11

Describe Integral proteins

Answer 11

Single or mulipass. Often alpha helical in secondary structure. Functions are receptors (sig and adhesion), channels, transport/pump

Question 12

Describe Peripheral Proteins

Answer 12

Outside PM but interact with IM/OM vi non-covalent. Part of cytoskeleton and cytochrome C.

Question 13

Describe Lipid Anchored Proteins

Answer 13

Either side with anchor to PM. Out=GPI, In= Fatty accetylation, Prenylation. Functions in Signal and Adhesion

Question 14

What are the various localization’s of Proteins

Answer 14

1. Apical - reg nuts, sec, protect, H20
2. Lat - Cell contact, adhesion, comm (TJs)
3. Basal - gas ion gradient and bm interaction

Question 15

Describe Membrane Asymetry and Movement

Answer 15

Asymmatry maintained by flipases. Scambalases activated during apoptosis. Mvmt in one plane common. EC= glycolipids and proteins, IC = phsophatidyl Serine (out during apop)

Question 16

Describe fluidity

Answer 16

Important for transport processes. Membrane maintained by H-phobic interactions and VDW forces. Increase fluidity by increase temp, increasing FA unsat, decreasing FA length, and decreasing Chol.

Question 17

Describe Lipid rafts

Answer 17

Rich in cholesterol and glycosphagolipid (long tail) therefore area is less fluid and thicker. Contains integral proteins and peripheral which cluster into functional groups.

Question 18

Describe RBC membrane skeleton

Answer 18

Glycophroin (1 pass) and Band 3 (multipass) are transmembrane proteins. Ankyrin bound to transmembrane proteins. Actin islands within cell are bound to protein 4.1. Spectrin alpha and beta interconnects 4.1 and ankyrin creating cytoskeleton

Question 19

What causes Acanthocytes (Spur Cell Anemia)

Answer 19

Abnormal lipoproteins with high cholesterol result in scallop RBC with many projections. This decreases deformation resulting in spleen destruction and haemolytic anemia

Question 20

What causes Hereditary Spherocytosis

Answer 20

Defect in Spectrin results in unstable membrane and deformation changes leading to haemolytic anemia