Chapter 8 - Cell Membrane

Question 1

Major components of cell membrane

Answer 1

1) phospholipid bilayer - saturated & unsaturated fatty acid
2) proteins - structural & functional diversity
3) cholesterol - fluidity buffer
* cannot flip-flop

Question 2

Unsaturated vs. saturated fatty acid

Answer 2

1) unsaturated
- prevent close packing
- allows membrane to be fluid
2) saturated
- close packing of F.A tails
- low fluidity (viscous)

Question 3

Functions of membrane protein

Answer 3

1) transport
- carrier, channel, pump
2) enzymatic activity
- ETC of aerobic respiration
3) signal transduction
- hormonal receptor
4) cell-to-cell recognition
- MHC, glycoproteins
e. g. ABO blood type antigen on surface of RBC
5) attachment to cytoskeleton & ECM (integrin)
6) intercellular joining (cell junctions)
a) tight junction
b) desmosome (rivet)
c) gap junction

Question 4

Passive transport

Answer 4

1) Diffusion
- movement of solute
a) simple diffusion
b) facilitated diffusion

2) Osmosis
- movement of solvent

Question 5

Diffusion

Answer 5

-movement of solute

a) simple diffusion
- CO2, and O2 (gas exchange in alveoli)

b) facilitated diffusion
* faster than simple diffusion
- large hydrophilic molecules
- aquaporin - water channel
- channel (voltage-gated, ligand-gated)
- carrier (revolving door)

Question 6

Osmolarity

Answer 6

concentration of system (cells)

Question 7

Tonicity

Answer 7

concentration of surrounding solutions that causes a cell to gain or lose H2O

hypertonic - conc. of solution is higher than cell
=cells lose water

hypotonic - conc. of solution is lower than cell
=cells gain water

Question 8

Normal osmolarity maintained in cells

Answer 8

300 mOsm

Question 9

Active transport

Answer 9

use electrochemical gradient

1) primary active transport
- electrogenic pump
- uses ATP
e. g. H+ pump in ETC, Na+/K+ pump in nerve axons

2) secondary active transport
- co-transport
- uses pre-existing concentration gradient
- transport protein couples downhill diffusion with uphill active transport

Question 10

Bulk transport

Answer 10

-active transport that moves large particles in large quantities

1) exocytosis
e. g. secretory proteins (made in rER), lysozyme, hormone

2) endocytosis
a) phagocytosis - pseudopodia
b) pinocytosis - drinking fluid
c) receptor-mediated endocytosis - triggered by binding of ligand to receptor