Plasma Membranes

Question 1

Phospholipid membrane

Answer 1

• Bilayer
• Proteins and cholesterol inserted

Question 2

4 components of cell membranes

Answer 2

1. phospholipid bilayer
2. surface proteins
3. transmembrane proteins
4. cell surface markers (glycoproteins, glycolipids)

Question 3

Differences in phospholipid bilayers

Answer 3

1. Less fluid with saturated fatty acids
2. Less fluid with long chain fatty acids
3. Sterols = fluidity buffers

Question 4

Membrane permeability

Answer 4

1. High = small uncharged polar molecules; gases
2. Medium = water
3. Low = ions; charged polar molecules; macromolecules

Question 5

Types of transmembrane transport

Answer 5

1. Passive
2. Active

Question 6

Passive transmembrane transport

Answer 6

1. Simple diffusion - movement of hydrophobic molecules with the concentration gradient; no ATP
2. Facilitated diffusion - molecules move through proteins
   
   • Channel proteins (pores)
     
     • Ion channels
     • Aquaporins (for water)
   • Carrier proteins
     
     • uniporter, symporter, antiporter.

Question 7

Types of osmotic concentration

Answer 7

1. Hypertonic – higher concentration of molecules outside; cells crenate (shrink)
2. Hypotonic – lower concentration of molecules outside; cells lyse (swell)
3. Isotonic – equal concentration of molecules

Question 8

Active transmembrane transport

Answer 8

Requires ATP; moves substances against the concentration gradient
- Sodium-potassium pump - 1 ATP = 3 Na+ outside, 2 K+ inside
- Indirect active transport

Question 9

Bulk transport

Answer 9

Endocytosis - phagocytosis, pinocytosis, receptor-mediated endocytosis

Exocytosis