Forces across membranes

Question 1

if a molecule is hydrophilic it is also…..

Answer 1

lipophobic (and vice versa)

Question 2

describe the general structure of membranes?

Answer 2

• embedded with glycoproteins
• embedded with glycolipids
• phospholipds contain hydrophilic phosphate heads and hydrophobic lipid tails
• cholesterol molecules stabilise membrane

Question 3

what are the function of glycoplipids in membranes?

Answer 3

used in self recognition (antigens) and the immune response

Question 4

what is the function of receptor proteins?

Answer 4

are intergral with allows communication between the ECF and ICF

Question 5

what is the function of peripheral membrane proteins?

Answer 5

• anchor membrane to cytoskeleton
• performs siganlling functions
• attch cell to exctracellular matrix

Question 6

which membranes have the lowest protein content?

Answer 6

myelin (18% protein)

Question 7

which membranes have the highest protein content?

Answer 7

membarens involved in energy transduction e.g inner membranes of mitochondria (~75%)

Question 8

what is the protein content of plasma membranes?

Answer 8

about 50%

Question 9

what are electrochemical gradients?

Answer 9

gradients resulting from the difference between electrical charge and concentration

Question 10

what are the concentrations of ions in the fluid compartments?

Answer 10

ECF: high Na+, low K+
ICF: Low Na+, high K+

Question 11

describe the process of endocytosis

Answer 11

invagination of cell membrane creates a vesicle which transports macromolecules inside cells

Question 12

what is the function of the cell membrane? (4)

Answer 12

• act as a selectively permeable barrier
• maintain concentration gradients
• provide site for receptors
• allows the transport of molecules

Question 13

what properties do molecules need to pass through the bilayer easily?

Answer 13

• small
• uncharged (non polar)
• lipophilic

Question 14

what type of channels allow passage of water

Answer 14

aquaporins

Question 15

describe the structure of open channels

Answer 15

form water filled pores thta allow the passage of water soluble molecules

Question 16

what two general types of channel proteins are there?

Answer 16

closed ion or open ion

Question 17

what two types of gated chennels are there?

Answer 17

voltage gated and ligand gated

Question 18

what is diffusion?

Answer 18

a process by which substances move between two compartments allowing the substance to spread across the whole volume giving equal concentrations

Question 19

how do carrier proteins function?

Answer 19

have binding sites for solutes, the binding of the solute causes a conformtaional change
- can only be open to ECF or ICF but not both at the same time

Question 20

what is movement through a carrier protein with the concentration gradient called?

Answer 20

facilitated diffusion

Question 21

what is movement through a carrier protein against a concentration gradient called?

Answer 21

active transport (requires ATP)

Question 22

how does the Na+/K+ ATP pump work?

Answer 22

is an electrogenic pump

- 3 Na+ out for every 2 K+ in

Question 23

how much of the bodeis resting energy used to power Na+/K+ pump?

Answer 23

40%

Question 24

what is osmosis?

Answer 24

the net movement of water from an area of high water concentration to an area of low water concentration

Question 25

what is the osmotic pressure?

Answer 25

the force required to oppose the increase in volume resulting form osmosis

Question 26

what is osmolarity?

Answer 26

the number of solute PARTICLES in solution

Question 27

what is osmolarity measured in?

Answer 27

osmoles (milliosmoles)

Question 28

what is the osmolarity of plasma

Answer 28

285 millisomoles (300)

Question 29

what is tonicity?

Answer 29

the number of NON-PENETRATING particles in soltution

Question 30

what terms can be used to describe solutions?

Answer 30

• hypotonic
• hypertonic
• isotonic
• hypoosmotic
• hyperosmotic
• isoosmotic

Question 31

what is the difference between osmolarity and osmolality?

Answer 31

OSMOLALITY: the number of solute particles per kg of solvent
OSMOLARITY: the number of solute particles per litre of solvent