transport and membrane

Exocytosis

used to fuse a

vesicle with the plasma

membrane and release

something outside the cell or

insert a transmembrane

protein in the plasma

membrane

Endocytosis

things are

engulfed and brought

into the cell in a vesicle

Phagocytosis

big stuff

Pinocytosis:

water

Receptor-mediated

specific to a

bond/interaction with a protein at

the membrane

Active transport

movement of a substance from

LOW  HIGH. This requires energy..

Secondary active transport

energy from one

thing moving passively down its gradient is

harnessed and used to power active transport of

another substance against its gradient

Symport

two substances are moved by a protein

helper in the same direction across the membrane

Antiport

two substances are moved by a protein

helper in opposite directions across the membrane

Primary active transport:

ATP provides energy.

The Na+/K+-ATPase (pump) is a good example.

• This is carrier-mediated and can saturate

ACTIVE

energy is required

Active transport of a substance from

LOW  HIGH requires energy input.

Primary active

uses ATP

Secondary active

uses passive

movement of another substance

diffusion

Thermal motion is random and

termed

passive

no energy input required

Simple diffusion

diffusion occurs straight

through the membrane. A helper protein is NOT

needed

– selective for specific ions

– Bidirectional – diffusion gradient

– Gated

• Open & close via conformational changes

ion channels are

electrochemical gradient

Ions move down their , when they move through ion

channels: this is a combination of their concentration AND electrical gradients

Passive Transporter

- must bind the solute

Bidirectional

net transport is

determined by gradient

No change in affinity

attraction to

glucose is same facing in or out of cell

for the glucose transporter (GLUT)

specific

only transports glucose

hydrophobic substances like lipids

what substance is happy to be on the inside of the bilayer with the fatty tails?

hydrophilic like ions and proteins

what kidns of substances would have greater difficulty crossing the cell membrane?

no. glucose is hydrophilic and would like to stay in water

glucose is a large charged molecule, will it easily move across the cell membrane?