Membrane Function and Structure

Question 1

Membrane Functions

Answer 1

Homeostasis/Compartmentalization
Transport
Intracellular Communication

Question 2

Compartmentalization - def

Answer 2

Maintaining concentration differences between compartments

Question 3

Intracellular Communication - types

Answer 3

gap junctions
transmitters
receptors
synaptic transmissions
excitablity

Question 4

Transporters (Cell Membrane)

Answer 4

Responsible for maintaining concentration differences across cell membranes

Question 5

Extracellular Fluid Concentrations

Answer 5

Na+ = 135-145 mM
K+ = 3.5-5.0 mM
Ca2+ = 2.0-2.6 mM
Cl- = 98 -106 mM

Question 6

Intracellular Fluid Concentrations

Answer 6

Na+ = 10 -15 mM
K+ = 140 mM
Ca2+ = 50 mM
Cl- = 10 mM

Question 7

Which ion concentrations are greater in extracellular fluid?

Answer 7

Na+ , Cl-

Question 8

Movement of Solutes - methods

Answer 8

Bulk Flow
Diffusion
Electrical Migration

Question 9

Excitable Cells use … to communicate

Answer 9

Action potentials, synaptic juntions

Question 10

Bulk Flow

Answer 10

bulk movement of solutions by hydrostatic pressure

Used for big disctances

Question 11

Diffusion - caused by, results in

Answer 11

Random thermal motion of molecules
Results in directed (net) movement of solutes when concentration differences exsist
Larger molecules diffuse more slowly than smaller ones

Question 12

Time to travel particular distance (x)

Answer 12

x2

Very inefficient over large distances

Question 13

Electrical Migration

Answer 13

Charge movement in response to an electric field.

Question 14

Electrodiffusion

Answer 14

Ions diffuse both by concentration and electrical attraction

Question 15

Flux

Answer 15

quantity that moves over a specified period of time

quantity/time

Question 16

Fick Law

Answer 16

Flux = P x A x deltaC

permeability x area x concentration difference

Question 17

Non Polar lipid soluble solutes

Answer 17

High permeability
Local anesthetics
alcohol
O2, Co2

Question 18

Ion permeability

Answer 18

Need help crossing membranes - use proteins (ion channels)

Question 19

Ionic Channels - factors affecting ion movement

Answer 19

chanels, conductance (ions/sec), Open probablity

Question 20

Protein mediated Transport - types

Answer 20

Facilitated Diffusion

Active Transport

Question 21

Facilitated Diffusion - def, types

Answer 21

Does not involve any use of metabolic energy
Channels
Carriers

Question 22

Channels - def, characteristics, amount

Answer 22

membrane protein molecules - pore that spans membrane
Open State & Closed State
Show specificity, saturation and competition
Millions of ions/second

Question 23

Carriers - def, method, amount

Answer 23

Membrane protein molecules
Binds solute to be transported, changes confirmation allowing solute to cross membrane
Show specificity, saturation and competition
thousands of ions/second

Question 24

Saturation - Tm, Vmax

Answer 24

Carrier will reach Tm, or transport maximum, with further increases in concentration not leading to increases in transport.
Vmax = maximum rate of reaction reached at high substrate levels where addition of substrate will no longer increase rate of reaction

Question 25

Active Transport - def

Answer 25

transport that can proceed AGAINST an electrochemical potential difference or can move transported solute 'uphill' Requires energy, usually ATP

Question 26

Active Transport - types

Answer 26

Primary AT | Secondary AT

Question 27

Primary AT - def, types

Answer 27

``` directly utilize metabolic energy = an ATPases or pump e.g. Na+/K+ pump Ca2+ pump H+ pump ```

Question 28

Na+/K+ pump - action, location

Answer 28

3 Na+ out of cell, 2K+ into cell | Basolateral membrane

Question 29

Ca2+ pump - location, action

Answer 29

ER of most cells (SR of muscle cell) , | Keeps Ca2+ within cell ?

Question 30

H+ pump - location, action

Answer 30

Basolateral membrane of specialized stomach cells or tubular cells of kidney Results in secretion of HCl during digestion.

Question 31

Secondary Active Transport - types

Answer 31

Co-transporters | Counter Transporters

Question 32

Co-Transporters

Answer 32

Move both solutes in the same direction

Question 33

Secondary Transporters - method, e.g.

Answer 33

Uphill movement of solute coupled with downhill movement of another solute (usually Na+) Na/glucose

Question 34

Counter Transporters - def., a.k.a

Answer 34

Move solutes in opposite directions | a.k.a exchangers

Question 35

Vesicle Mediated Transport - types

Answer 35

Exocytosis | Endocytosis

Question 36

What undergoes Exocytosis ?

Answer 36

synaptic transmitters, hormones and some digestive enzymes

Question 37

Receptor mediated endocytosis

Answer 37

material to be transported first binds to a receptor and the substance-receptor complex is ingested by endocytosis

Question 38

Osmosis - def. how,

Answer 38

Diffusion of water | through lipid bylayer, ionic chanels and aquaporins

Question 39

measurning water concentration

Answer 39

measured in terms of concentration of dissolved solute particles

Question 40

Osmolarity

Answer 40

solution of concentration of dissolved particles in the solution physical property labeling osmolarity is relative

Question 41

Tonicity

Answer 41

based on steady state cell volume biological property affected by permeability