Membrane

Question 1

Outer boundary of membrane size

Answer 1

5-10 nm

Question 2

How we can see the membrane?

Answer 2

Too small therefore inly can be seen by electron microscopes

Question 3

Bilayers stabilized by

Answer 3

Van der waals interactions in the fatty acyl chains

Question 4

Polar head stabilize by

Answer 4

Ionic and HB bonds of polar heads with each other and with water

Question 5

Plasma membrane components

Answer 5

1-lilid bilayer
2- proteins — individual and complex proteins— penetrate and extend out

Question 6

Lipid bilayer fluid or rigid?

Answer 6

Fluid

Question 7

Plasma membrane vs internal membrane

Answer 7

Plasma: outer boundary of cell
Internal: enclosed compartments (organelles)

Question 8

Cell membrane functions

Answer 8

-compartmentalization
-framework
-selective permeability
-solute transport
-response to external stimulus
-cell-cell communication
-energy transduction

Question 9

Lipid to protein ratio depends on

Answer 9

1- type of cellular membrane
2- type of organisms
3- type of cell

Question 10

Lipid kinds in membrane

Answer 10

1- phosphoglycerides
2- sphingolipids
3- cholesterol

Question 11

Phosphoglyceride

Answer 11

2 fatty acids (1 saturated-1 unsaturated)
1 glycerol
1 phosphate
Most have small hydrophilic group linked to phosphate
- amphipathic
- kinds:
1- phosphatidylethanolamine
2- phosphatidylserinr
3- phosphatidylcholine

Question 12

Phosphatidylserine

Answer 12

Net negative charge

Question 13

Sphingolipids

Answer 13

Derivative ceramide
Carbohydrates are added — glycolipid
Multiple sugars added — ganglioside

Question 14

Glycolipids

Answer 14

Exclusively on exoplasmic face
Have glycolipids with glycerol back bine but we mean glycosphingolipids

Question 15

Where glycolipids are made

Answer 15

Lumen of golgi (consider equivalent to outside of cell)
Exocytosis and add to exoplasmic face

Question 16

Sterols

Answer 16

50% of membrane
Most important: cholesterol (amphipathic)

Question 17

Membrane folding

Answer 17

Unfavorable planar position
Fold spontaneously—> lipososomes
Membranes are always continuous-hydrophobic tail doesn’t like water

Question 18

Phophatidylserine

Answer 18

Protein requires them on cytosolic face
During apoptosis move to exoplasmic face and signal neighbors

Question 19

Plasma membrane contains:

Answer 19

(2-10)% carbohydrates
90% glycoproteins
10% glycolipids

Question 20

Mebrane carbohydrates

Answer 20

Face to exoplasmic face

Question 21

Addition carbohydrate to protein

Answer 21

Glycosylation
Most complex post transitional modification

Question 22

Membrane proteins

Answer 22

1- integral (pass through)
2- peripheral (non-covalently bind to either sides)
3- lipid-anchored proteins (covalently bind to lipid membranes)

Question 23

Integral proteins function

Answer 23

1- transporters
2- anchors
3- receptor
4- electron transporter

Question 24

Integral protein

Answer 24

• amphipatic
• hard to isolate in soluble form
• glycophorin A: major erythrocyte plasma membrane
  Transmembrane domains: 20 non-polar aAA as alpha helix span in lipid bilayer
• positively charged arg and lys near cytosolic face anchor the protein

Question 25

Hydropathy plot

Answer 25

Hydrophobicity AA determine
Positive value = hydrophobic
Always from N-terminus to C-terminus

Question 26

Peripheral proteins

Answer 26

Associated with integral protein or lipid polar head
Readily can be removed by:
- change ph
- change ionic strength

Question 27

Lipid anchored proteins

Answer 27

1- fatty-acid anchored — synthesized in cytosol ACYLATION
2- isoprenylated membrane — synthesized in cytosol PRENYLATION(have arms)
3- gpi-anchored — synthesized in ER

Question 28

Cholesterol

Answer 28

Hydroxyl near polar head membrane

Question 29

Cholesterol function

Answer 29

1- decrease permeability to ions and small polar molecules
2- fluidity buffer

Question 30

Saturases

Answer 30

Change number of fatty acids double bonds

Question 31

Homeoviscous adaptation

Answer 31

Cell regulate membrane fluidity in response temperature changes by altering lipid composition and maintain fluidity

Question 32

Lipid rafts

Answer 32

Localized membrane lipid with specific proteins
In ANIMAL outer monolayer has more cholesterol and sphingolipids (longer)
Lipid rafts are thicker

Question 33

Lipids movement

Answer 33

— lateral diffusion
— rotation
— transverse diffusion

Question 34

Flippases

Answer 34

Enzyme need for transverse movement