7B- Channels and transporters

generally it is slightly more ( ) inside of the cell due to ( )

negative

nucleic acids & metabolites & ions

look at slide 5

bruh

pure ( ) serve as barriers for large and/or charged molecules

phospholipid bilayers

Why is it important for cells to restrict movement in and out?

-Control activities/functions 

-enhance binding n certain areas of the cell

-organization/grouping of proteins for a specific function

and prevent activities that are detrimental 

-proper signaling

-causes polarity of cells

proteins in membranes ( ) molecules across the membrane- many span the membrane, they are called what?

transport

trans-membrane proteins

Impermeable molecules are moved using ( ) , which are often proteins complexes- often ( )

transporters or channels

multimers

look at slide 9

okayyyy 

transporters/carriers requires ( ) for each molecule passing through

conformational change

channels, once open, molecules can ( ), no further conformational change is needed

pass through

both transporters/carriers and cannels are ( ) 

selective 

transporters can be one of three types, what are they?

uniporter

symporter

antiporter

( )- moves just molecule to be transported 

( )- moves molecule to be transported ALONG with co-transported molecule in SAME direction 

( )- moves molecule to be transported ALONG with another molecule in opposite directions 

uniporter

symporter

antiporter

Passive transporter- moves solutes with/down their ( ) and this does not require ( )

concentration gradient

energy

model for how ( ) in transporter could ( ) 

conformation change 

mediate passive movement of solute

There are 2 ways ions or molecules are moved across the membrane:

• ( )- does not require energy, because movement is ( ) concentration gradient

• ( )- requires energy, because movement is ( ) concentration gradient

passive transport

down/with

active transport

up/against

active transporter- moves ( ) up/against their concentration gradient

solutes (simple ions or molecules-which can be ions too)

Active transport requires energy from one of 3 sources, what are they?

1) co-transport/ coupled transport- down a gradient- can be antiport or symport

2) often ATP is used

3) light energy also used 

Na+/K+ATPase is an ( ), consumes ~ ( ) of resting cell’s ATP, pumps ( ) out and ( ) into cell, both ( )

active antiporter

60

Na+

K+

AGAINST concentration gradient

Often active transport across the plasms membrane is “coupled” to ( ) gradient, to move glucose against its ( ), energy comes from movement of ( ) down/with a concentration gradient (symport here)

Na+

concentration gradient

Na+

look at slide 17-18

okay

Trans-cellular (across the cell) transport of glucose in intestines:

-active, ( ) transport to get glucose into ( )

-passive transport to get glucose from intestinal epithelium cell to ( )

symport

intestinal epithelium cells

extracellular fluid

Ion channels passively allow rapid ( ) of ( ) down their concentration gradient, but this is usually controlled by a “( )“

diffusion

ions

gate

some channels are gated, gates open due to what changes and what is the name of the gate?

voltage-gated: voltage changes

ligand-gated (extracellular ligand): ligand binds outside

ligand-gated (intracellular ligand): ligand binds inside

mechanically gated: mechanical deformation of membrane

Voltage-gated Na+ channels are responsible for ( ) in ( ), when open, ( ) due to opening channels and ion movement. 

action potentials

nerves

polarity switches 

look at slide 28-30

okayyy

( ) act at neuromuscular junctions to control ( )

acetylcholine-gated (so ligand-gated) cation channel

(so both a ligand-gated ion channel and ion-channel-coupled receptor)

control muscle contractions

( ) at the neuromuscular junctions to control ( ) 

many events 

muscle contraction

( ) cation channels act at neuromuscular junctions to control muscle contraction

Acetylcholine-gated (ACh-gated- so ligand gated)