Topic 2 - CELL PHYSIOLOGY I (The Cell Membrane)

Question 1

Name the 3 parts of the cell membrane

Answer 1

1. Phospholipid Bilayer
2. Membrane Proteins
3. Membrane Carbohydrates

Question 2

Phospholipid Bilayer

Answer 2

• continuous layer around cell
• barrier to water soluble substances - NOT to small molecules (CO₂ & O₂) and lipid soluble molecules

Question 3

Membrane Proteins

What are the 5 types?

Answer 3

1. Transport proteins
2. Receptor proteins
3. Enzymes
4. Joining proteins
5. Identifying proteins

Question 4

Transport Proteins: Channels

List 3 characteristics

Answer 4

1. form pore in membrane
2. selectively permit channel-mediated fasciliitated diffusion of water & specific ions
3. can be:
   
   • gated: can open or close - in response to stimuli
   • non gated: = “leakage channel” - always open

Question 5

fascilitated diffusion is referred to what type of transport protein?

a) channels
b) carrier proteins

Answer 5

channels

Question 6

fascilitated transport is referred to what type of transport protein?

a) channels
b) carrier proteins

Answer 6

carrier proteins

Question 7

active transport is referred to what type of transport protein?

a) channels
b) carrier proteins

Answer 7

carrier proteins

Question 8

Transport Proteins: Carrier proteins

list 2 characteristics and an example

Answer 8

1. bind solute and carry it across membrane
2. allow protein carrier-mediated fascilitated transport or active transport

example: glucose transporters

Question 9

Receptor proteins

List 1 characteristic

Answer 9

• can bind specific extracellular molecules (=ligands)
  
  • e.g. hormones, neurotransmitters

Question 10

name an example of how a receptor protein works

Answer 10

glucose uptake:

step 1: insulin binds to receptor on skeletal muscle or adipose tissue

step 2: triggers movement of more glucose transporters to cell membrane

step 3: increasing glucose movement from blood into cells

Question 11

enzymes

list 1 characteristic and 2 examples

Answer 11

• control chemical reactions on outer or inner surface
• e.g. 1: acetylcholinesterase
• e.g. 2: Na⁺/K⁺ - ATPase - all cells have these

Question 12

Joining Proteins

Answer 12

• anchor cell membrane to cytoskeleton or an adjacent cell
  
  • i) junctional proteins between cells forming:
    
    • desomomes, tight junctions, gap junctions
  • ii) extracellularfibres (usually glycoproteins)

Question 13

Identifying Proteins

Answer 13

e.g. Major Histocompatibility Complex (MHC) proteins

• on surface of all cells except rbc
• identify cell as self (part of the body) - not foreign

Question 14

Membrane Carbohydrates

Answer 14

• glycoproteins and glycolipids
• differ for every cell type - allow cells to recognize type.
  
  • e.g. sperm recognizes egg