Week 3 Ch. 4

Question 1

Cell membranes model

Answer 1

mosaic model
flexible membraes

Question 2

Factors of molecule transport across cell membranes

Answer 2

1. Membrane permeability
2. molecular gradients
3. Transport mechanisms (membrane pound proteins)
4. Ion channels

Question 3

Membrane permeability

Answer 3

How far into membrane substances can go

Question 4

High membrane permeability:

Answer 4

O2 and CO2
N2

Question 5

No membrane permability

Answer 5

Ions, glucose

Question 6

Diffusion occurs

Answer 6

down a concentration gradient
high–>low

*no ATP needed

Question 7

Diffusion through a lipid bilayer

Answer 7

Requires a protein channel or carrier
*no ATP needed

Question 8

Active transport

Answer 8

occurs against concentration gradient

involves a protein carrier

*Requires ATP/energy

Question 9

Lipid solubility and rate of diffusion

Answer 9

increased lipid solubility = increased rate of diffusion

Question 10

What soluble molecules cross membrane via

Answer 10

channels or protein transport

Question 11

What factors influence diffusion?

Answer 11

-Membrane pores (diameter and size)
-Electrical charge (selectivity) - i.e. potassium channel

Question 12

Potassium Channels MOA

Answer 12

Carbonyl oxygens in selective filter

Carbonyl grabs water that K is surrounded by and pulls K and water apart. K is sucked into channel

Na will not lose water so it just leaves

Question 13

Sodium channel MOA

Answer 13

Inner surface of channel is lined with negatively charged AAs - pulls dehydrated sodium into channel (pulls sodium away from water)

“all or non”, open or closed

Question 14

Facilitated diffusion

Answer 14

Transport molecule binds to binding point inside channel

entryway from ECF closes, entryway into cell opens

Molecule releases from binding side and goes into cell

Question 15

Rate of facilitated diffusion is limited by

Answer 15

Vmax of carrier protein

So facilitated diffusion has a max amount of molecules it can bring in, diffusion rate plateaus off once reached
If you need more molecule, you need addition carrier protiens

Question 16

Factors that affect net rate of diffusion:

Answer 16

1. Concentration gradient
2. electrical potential
3. Hydrostatic pressure

Question 17

Electrical potential

Answer 17

Explained by Nerst potential

Question 18

Nerst Potential

Answer 18

Equilibrium potential

“At what point will the negatively charged molecules stop entering the cell?”

Question 19

Hydrostatic pressure factor

Answer 19

Higher pressure results in increased energy available

net movement from high to low pressure

Question 20

Osmosis

Answer 20

water–>salt concentration

Question 21

Osmotic pressure

Answer 21

amount of pressure required to counter osmosis

attributed to the osmolarity of solution

Question 22

tonicity vs osmolarity

Answer 22

Tonicity takes into account the properties of the solute AND permeability of a membrane

Question 23

Tonicity is also called

Answer 23

Effective osmotic pressure

Question 24

Active transport

Answer 24

requires ATP (energy) to move substances in or out of cell

depends on carrier proteins

Question 25

Primary active transport

Answer 25

energy is derived from direct breakdown of ATP

Question 26

Secondary active transport

Answer 26

energy comes from stored energy of ionic concentration differences between two sides of the membrane

Question 27

Active transport example

Answer 27

Na+-K+ pump

Question 28

Na-K pump helps:

Answer 28

Maintain negative electrical voltage inside cell (3 Na+ out, 2 K+ in = more negative on the inside)

can run in reverse to generate ATP

Question 29

Calcium pumps

Answer 29

One pump pumps Ca2+ out of cell, another pumps Ca2+ into organelles (sarcoplasmic reticulum and mitochondria)

Question 30

Hydrogen ion transport

Answer 30

Pull in H+ against concentration gradient

-gastic glands
-renal tubules (release or pull in H+ to maintain urine pH)

Question 31

Contratransport

Answer 31

Occurs due to concentration gradients formed on either side of plasma membrane

One substance pulls another in with it when moving into cell

i.e Na+ and glucose

Question 32

Countertransport

Answer 32

Substance moves into cell and uses energy to propel a second substance out

i.e. Na+ and Ca+

Question 33

Co-transport

Answer 33

Conformational change of carrier protein will not occur unless both substances are present

i.e. Glucose and Na+ ions