BC 5 Cell Membranes

Question 1

Cell Membrane Permeability

Answer 1

Restricts certain molecules.

Small Hydrophobic Molecules Allowed
Gases, oxygen, carbon dioxide

Small polar can as well but slowly

RESTRICTED: highly charged, ions, large molecules, sugars, amino acids (require transport proteins

Question 2

Amphipathic

Answer 2

Hydrophobic and Hydrophilic ie Lipids

Question 3

Major Cell Membrane Lipids (Structure)

Answer 3

Glycerophospholipids: 2 Fatty Acid Tails -> {{Glycerol -> Phosphate -> Choline}} Polar
- Phosphotidylcholine

Sphingolipids: 1 Fatty Acid Tail -> Sphingosine (1 FA + Head) Phosphate -> Choline

Cholesterol: Short Fatty Acid Tail -> Rigid steroid Ring Structure

Question 4

Glycerophospholipids:

Answer 4

Most Abundant Lipid

14-24 Carbon Atom Chain

One hydrophobic tail usually has one or more Cis bonds (unsaturated)

Ester linkages to fatty acid tails (Choline also ester linked)

Named by head group: Phosphotidyleserine, choline etc…

Question 5

Sphingolipids

Answer 5

Sphingosine Backbone instead of glycerol, already has one FA tail

Sphingosine + FA = Ceramide

Phospholipid bc contains phosphorous

major of outer leafelet

Question 6

Glycolipids

Answer 6

Sphingolipids that contain carbohydrate (COH) chains

nerve Tissues

Only in outer leaflet, carb exposed

Cerebrosides: Nerve Tissue/Brain

Gangliosides (acidic glycosphingolipids) Ganglion cells, involve accumulation of NANA containing cells

Question 7

Cholesterol

Answer 7

Amphipathic

Small poplar head, rigid steroid ring, non polar hydrocarbon tail

Membrane fluidity

Both leaflets

high in RBC/liver

Question 8

5 Membrane Fluidity Actions

Answer 8

Lateral Diffusion: move in plane

Rotation: rotate on axis

Swing: Just Tail

Flexion: contraction of tail (cushion)

Transverse: flip flop, helped by flippases

1. UNSATURATED(kinked) 2. length 3. high Temp 4. Cholesterol (rigid at high T/flex at low T) prevents freezing

Question 9

4 Major Cell Membrane Activities

Answer 9

Transport
Catalysis: of membrane associated reactions (atp)
Structural Links: To cytoskeleton or ECM
Receptors

Question 10

Peripheral Proteins & Membrane Protein Mobility

Answer 10

Loosely Associated to Membrane via H Bonds or Electrostatic Forces

Mobility: Restructed by rafts, tight junctions, ECM interactions, Cytoskeletal attachments

Question 11

Membrane Carbohydrates

Answer 11

ONLY on the extracellular leaflet, covalently attached to proteins and lipids

Make up Glycocalyx (carb rich zone outside cell) (glycol-bound to sugar: glycolipids/glycoproteins etc)
-cell recognition/signaling occur here/absorbs water, becomes slimey (motile), narrow passes, cushion/ endothelial, RBC, platelet/determines ABO/blood clotting/sperm-egg int

Glycocalyx: Formed by enzymatic Glycosylation (non enzymatic, glycation)

microvilli covered by thick glycocalix in intestine, contains glycosylated enzymes for breakdown and absorbs, friction protection

Question 12

Cell Membrane Defects (associated diseases)

Answer 12

Lipid Associated:
MS: Autoimmune Myelin Sheath (Sphingomyelin/Galactocerebrosides)

Niemann-Pick: hereditary, deficiency of sphingomyelinase, accumulation in liver, spleen, lunchs, bone marrow, brain, neuro problems
A. Infants, Jaundice, enlarged liver, brain damage 18mo
B. enlarged liver and spleen, preteen, brain not affected, less than 1% levels of enzyme compared to norm.
C. different mutation, buildup of cholesterol in liver, spleen and neural cells

Sphingolipidosis: Fabry X linked, Krabbe, Gaucher, Tay Sachs, Metachromatic leukodystrophy. Inherited
high in Ashkenazi Jews, enzyme replacement therapy helps lots, infantile fatal.

Cystic Fibrosis: Membrane protein, Cl- transporter defective-abnormally think mucus obstructs airways. CFTR gene ABC family

Congenital Disorders Glycolation : CDG- carbohydrate disorders. Either missing oligosaccharide chains or abnormal ones. Manifest broadly,.