Movement Across Cell Membrane

what are the functions of the cell membrane?

• to provide structure

• to protect the cellular contents from the environment

• allows cells to act as specialized units

what does the semi-permeability of the cell membrane control?

controls what molecules can and cannot pass through the membrane

what is the difference between passive and active transport?

passive does not use energy, active does

what is diffusion?

the movement of particles DOWN their gradient (from high concentration to low concentration)

what is osmosis?

movement of water molecules down the gradient (from high to low concentrations)

what are the 2 types of diffusion?

Simple diffusion and facilitated diffusion

Simple diffusion

molecules move down their gradient without any help

what kind of molecules undergo simple diffusion?

small and non polar molecules

true or false: simple diffusion can be disrupted if diffusion distance is increased?

TRUE

facilitated diffusion

diffusion that gets helped along the way. usually involves a membrane transport channel

glycoproteins

the membrane transport channels that are often used in facilitated diffusion, have a carbohydrate attached that allows molecules to pass through the membrane.

true or false: membrane transport channels are not specific to certain molecules

false- channels are specific to certain molecules

Active transport

when the body needs to move the molecules AGAINST the gradient (uphill) and requires energy to do so.

example of active transport?

Sodium, potassium pump

what is the energy from the breakdown of ATP used for in regards to the sodium potassium pump?

the energy is used to pump 3 sodium ions out of the cell and 2 potassium ions into the cell

primary active transport

just needs some ATP to activate the transport process

secondary active transport

going against the gradient, uses other molecules in addition to ATP to move across the membrane