Cell Membrane and Transport

Question 1

interstitial fluid

Answer 1

ECF that surrounds cells

Question 2

functions of membrane proteins

Answer 2

1) transport
2) receptors for signal transduction
3) attachment to cytoskeleton and extracellular matrix
4) enzymatic activity
5) intercellular joining
6) cell-cell recognition

Question 3

Tight junctions

Answer 3

neuro (BBB)

prevent fluids and most molecules from moving b/w cells

Question 4

Gap junctions

Answer 4

cardiac

transmembrane proteins form pores that allow small molecules to pass from cell to cell

Question 5

Determinants of passive permeability

Answer 5

lipid solubility, channels of appropriate size, carrier proteins

Question 6

Simple Diffusion

Answer 6

non-polar lipid soluble substances diffuse directly through phospholipid bilayer

Question 7

Facilitated Diffusion

Answer 7

(passive) certain lipophobic molecules (glucose, amino acids, ions) use carrier proteins or channel proteins

Question 8

Two types of channel proteins

Answer 8

• leakage channels (K) always open

- gated channels (Na) controlled by chemical/electrical signals

Question 9

Osmosis

Answer 9

movement of water across SPM, either through lipid bilayer or through aquaporins; water concentration determined by solute concentration

Question 10

Osmolarity

Answer 10

measure of total concentration of solute particles

Question 11

Two types of active processes

Answer 11

active transport
vesicular transport
(both use ATP to move solutes across membrane)

Question 12

Active Transport

Answer 12

requires carrier proteins- moves solutes against gradient

Question 13

Primary active transport

Answer 13

energy from hydrolysis of ATP causes shape change in transport protein so that bound ions are pumped across membrane (Na/K pump)

Question 14

Secondary Active Transport

Answer 14

depends on an ion gradient created by primary active transport- energy stored in ionic gradients used indirectly to drive transport of other solutes

Question 15

Cotransport

Answer 15

• secondary active transport
• symport- 2 substances transported in same direction
• antiport- 2 substances transported in opp direction

Question 16

Vesicular Transport

Answer 16

transport of large particles, macromolecules, and fluids across plasma membranes- requires ATP

Question 17

Functions of Vesicular Transport

Answer 17

• exocytosis- out of cell
• endocytosis- into cell
• transcytosis- into, across, then out of cell
• substance (vesicular) trafficking- transport from one area/organelle to another

Question 18

Examples of exocytosis

Answer 18

hormone secretion, NT release, mucus secretion, ejection of wastes

Question 19

Membrane Potential

Answer 19

Separation of opposite charged particles across membrane (measured as voltage)

Question 20

Generation/maintenance of RMP

Answer 20

1) Na/K pump continuously ejects Na from cell and carries K back in
2) some K leaks out constantly
3) membrane interior becomes neg because of large anions trapped inside cell
4) electrochemical gradient attracts K into cell
5) RMP est. at point where gradient balances K gradient
6) steady state maintained b/c rate of active transport = to and depends on rate of Na diffusion into cell

Question 21

Roles of Membrane Receptors

Answer 21

• contact signaling
• chemical signaling
• G protein linked receptors

Question 22

contact signaling

Answer 22

touching/recognition of cells; normal development and immunity

Question 23

chemical signaling

Answer 23

interaction b/w receptors and ligands to alter activity of cell proteins

Question 24

G protein linked receptors

Answer 24

ligand binding activates G protein, affecting ion channel or enzyme or causing release of internal second messenger (like cAMP)