Ch 3, 3 Membrane transport Flashcards Preview

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Flashcards in Ch 3, 3 Membrane transport Deck (31):
1

general functions of plasma membrane

1. selectively permeable-only allows certain molecules through
2. controls movement of materials in and out- how much and when?
3. maintains homeostasis- maintaining sable internal conditions in the body

2

passive processes

no cellular energy (ATP) is required
substance moves down concentration gradient

3

passive characteristics

a. its solubility
-lipid soluble(hydrophobic) substances can diffuse through the phospholipid bilayer
-water soluble (hydrophilic) can not, must use channels or carriers
b. its size
-are there channels in the membrane the appropriate size?
-large lipid molecules cannot get through eg. large proteins
c. Presence of suitable carrier proteins in the membrane
-membrane carrier proteins are specific, can only bind to certain molecules

4

filtration

passive process
-movement against a fluid pressure gradient
materials are carried along with the fluid from a area of high fluid pressure to low fluid pressure

5

simple diffusion

passive process
-non polar(hydrophobic) substances diffuse directly through the phospholipid bilayer following a concentration gradient
-kinetic energy of the molecules cause them to move, random movement
1. higher conc. higher the rate
2. bigger the molecule, slower the rate
3. higher the temp, higher the rate

6

facilitated diffusion

passive process, with carriers or channel proteins
certain hydrophilic molecules use specific carrier or channel proteins to pass through the membrane, eg. glucose, amino acids, ions
-this type of diffusion is..
a. specific
b. rate Is determined by number of carriers or channels
c. rate can be regulated
d. substances can only move with a concentration grad. from high to low

7

using carrier proteins

transmembrane integral proteins transport specific polar molecules (sugars and amino acids)
binding of substrate causes shape change in carrier

8

using channel proteins

aqueous channels formed by transmembrane proteins selectively transport ions or water
two types-
a. leakage channel-always open
b. gated channels- controlled by chemical or electrical signals

9

osmosis

passive process
diffusion of water across a selectively permeable membrane

10

two ways water diffuses through plasma membrane

through the lipid bilayer--wiggles between the phospholipids
through protein channels called aquaporins (AQPs)

11

water diffusion

from high concentration to low

12

aqueous diffusion

water concentration depends on solute concentration- the higher the solute conc. the lower the water (solvent) conc.

13

importance of osmosis

when it occurs, water enters or leaves a cell
change in cell volume disrupts cell function
eg, water enters the cell swells

14

Tonicity

comparative terms used to describe relative concentration of solutes in two different aqueous solutions

15

isotonic solutions

2 solutions with the same solute concentration

16

hypertonic

a solution having a greater solute concentration than another solution

17

hypotonic

a solutions with a lower solute concentration than some other solution

18

effects of isotonic on RBC

no change, water moves equally

19

effects of hypertonic on RBC

cell shrinks
water moves out
loses volume
"crenated"

20

effects of hypotonic on RBC

water moves in
cell bursts
"lysed"

21

osmolarity

the measure of the total concentration of all solute particles in a solution

22

active process

requires carrier proteins (solute pumps)
moves solute against a concentration gradient
requires energy output by cell (ATP)

23

primary active

energy comes directly from hydrolysis of ATP
causes shape change in transport protein so that bound solutes (ions) are pumped across
eg. sodium/potassium pump
in all plasma membranes..essential for muscle and nerve function

24

secondary active

depends on ion gradient crated by primary active transport
energy stored in ionic gradients is used indirectly to drive transport of other substances

25

co transport

active process
always transports more than one substance at a time

26

symport system

two substances transported in same directions

27

antiport system

two substances transported in opposite directions

28

vesicular active transport

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

29

exocytosis

vesicular transport
transport out of cell, large protein, hormones, mucus

30

endocytosis

transport into the cell..3 types
1. phagocytosis; solid materials are engulfed by pseudopods and brought in to interior cell, carried out by some WBC
2. pinocytosis; liquids and solutes brought into cell by infolding of plasma membrane
-occurs during nutrient absorption in small intestine
3. receptor mediated endocytosis; specific protein receptors in membrane bind to substances
-uptake of enzymes, hormones and cholesterol

31

transcytosis

transport into, then across then out of the cell