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Flashcards in Membrane Function and Structure Deck (41):
1

Membrane Functions

Homeostasis/Compartmentalization
Transport
Intracellular Communication

2

Compartmentalization - def

Maintaining concentration differences between compartments

3

Intracellular Communication - types

gap junctions
transmitters
receptors
synaptic transmissions
excitablity

4

Transporters (Cell Membrane)

Responsible for maintaining concentration differences across cell membranes

5

Extracellular Fluid Concentrations

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

6

Intracellular Fluid Concentrations

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

7

Which ion concentrations are greater in extracellular fluid?

Na+ , Cl-

8

Movement of Solutes - methods

Bulk Flow
Diffusion
Electrical Migration

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Excitable Cells use ... to communicate

Action potentials, synaptic juntions

10

Bulk Flow

bulk movement of solutions by hydrostatic pressure
Used for big disctances

11

Diffusion - caused by, results in

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

12

Time to travel particular distance (x)

x2
Very inefficient over large distances

13

Electrical Migration

Charge movement in response to an electric field.

14

Electrodiffusion

Ions diffuse both by concentration and electrical attraction

15

Flux

quantity that moves over a specified period of time
quantity/time

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Fick Law

Flux = P x A x deltaC
permeability x area x concentration difference

17

Non Polar lipid soluble solutes

High permeability
Local anesthetics
alcohol
O2, Co2

18

Ion permeability

Need help crossing membranes - use proteins (ion channels)

19

Ionic Channels - factors affecting ion movement

# chanels, conductance (ions/sec), Open probablity

20

Protein mediated Transport - types

Facilitated Diffusion
Active Transport

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Facilitated Diffusion - def, types

Does not involve any use of metabolic energy
Channels
Carriers

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Channels - def, characteristics, amount

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

23

Carriers - def, method, amount

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

24

Saturation - Tm, Vmax

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

25

Active Transport - def

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

26

Active Transport - types

Primary AT
Secondary AT

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Primary AT - def, types

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

28

Na+/K+ pump - action, location

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

29

Ca2+ pump - location, action

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

30

H+ pump - location, action

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

31

Secondary Active Transport - types

Co-transporters
Counter Transporters

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Co-Transporters

Move both solutes in the same direction

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Secondary Transporters - method, e.g.

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

34

Counter Transporters - def., a.k.a

Move solutes in opposite directions
a.k.a exchangers

35

Vesicle Mediated Transport - types

Exocytosis
Endocytosis

36

What undergoes Exocytosis ?


synaptic transmitters, hormones and some digestive enzymes

37

Receptor mediated endocytosis

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

38

Osmosis - def. how,

Diffusion of water
through lipid bylayer, ionic chanels and aquaporins

39

measurning water concentration

measured in terms of concentration of dissolved solute particles

40

Osmolarity

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

41

Tonicity

based on steady state cell volume
biological property
affected by permeability