Lec. 10 - Membrane Transport

What can passively cross cell membrane?

small nonpolar molecules: oxygen, CO2, nitrogen gas

What can actively cross cell membrane?

large polar molecules: glucose, amino acid, ATP

What does cell being selectively permeable mean?

cell chooses what goes in/out

Define active transport

moving something AGAINST the concentration gradient with the help of ATP (low to high)

Define passive transport

moving something down concentration gradient without help of ATP (high to low)

Define diffusion

movement of molecules from high to low concentration gradient to reach equilibrium

Osmosis

diffusion of free water

A solution is hypertonic if...

water exits cell and it shrivels

A solution is hypotonic if...

more water goes in cell and it bursts

A solution is isotonic if...

the same amount of water is inside as outside of cell

What is tonicity?

What water will do in different solutions

Define aquaporins

channel proteins for water, facilitated diffusion

What are simple and facilitated diffusion both types of and what is the difference?

passive transport. simple = no transport proteins helping. facilitated = requires transport proteins

What type of proteins does Active transport require?

Carrier proteins

How does Sodium move across cell membrane?

Na+/K Pase Sodium Potassium Pump

Define Sodium potassium pump

primary active transport, pumps potassium in and sodium out with phosphorylation

What is the sodium potassium pump ratio?

2K in and 3Na+ out

Why is the sodium potassium pump a primary active transport?

because it directly attaches to transporter (ATP)

Define Phosphorylation

a hydrogen reaction occurs, removing a phosphate group from ATP. Then phosphate group attaches to protein changing its shape.

What is the sodium potassium pump responsible for?

maintaining cell's membrane potential

define membrane potential

difference in chemical and electrical potential energy on either side of a cell membrane.

What do the brackets mean: [Na+]

the "concentration of" Na

Define action potential

when a lot of Na+ goes into a cell prompting it to all get pushed out

Define Chemical Potential energy

difference in chemical concentration on two sides of the membrane

Define Electrical potential energy

difference in number of charges on two sides of membrane

What is the resting membrane potential (electrcial)

-70mV

What kind of ion would want to go into an overall negative cell?

positive ion

Define Voltage-Gated Ion Channel

responds to changes in voltage, then allows (or disallows) ions to flow in/out

Is Voltage-Gated Ion Channel active or passive?

passive, does not require ATP, cannot carry ions against gradient

Define carrier proteins

move ions against concentration gradient (like hands)

Define channel proteins

move things down/with concentration gradient

Define Proton (H+) pump

push (H+) out of cell, active transport, found in stomach where lots of acid

Basic =

less (H+)

Acidic =

more (H+)