Cellular Transport

*This is another function of the cell membrane—what a job!

I. Cellular transport is the study of how particles move into and out of the cell

A. Remember: in order to maintain homeostasis (a steady state) within the cell, the cell must constantly move things into and out of itself. The cell membrane is structured in such a way to help with this process.

Picture 1: Let’s draw a cell membrane! Make sure it has a

phospholipid bilayer, 1 transport protein, 1 identifying protein, 2 cholesterol molecules, and 3 inner surface proteins.

B. We call this model of the cell membrane the fluid mosaic model. The cell membrane is not still—it is always moving (as we saw on the computer). The cell membrane can look slightly different at any time (mosaic).

II. Two main types of cellular transport

A. Passive TransportB. Active Transport

III. Passive Transport

A. Passive transport is the movement of particles across the cell membrane (in or out of the cell) with the concentration ([ ]) gradient.

1. With the concentration gradient means from high to low concentration.

Passive Transport

Picture 2:

Cell membrane

2. This means that the particles move from an area where there is a lot of something to an area where there is a 1 to 1 ratio of that same thing until there are equal or correct amounts on both sides of the membrane.

3. Passive transport does not require energy in the form of ATP in order to occur.

B. Types of Passive Transport

1. Simple Diffusion: the movement of

small particles straight across the phospholipid bilayer. Ex. O2 & CO2

2. Osmosis: the movement of water

molecules straight across the phospholipid bilayer.

3. Facilitated Diffusion: the movement of larger particles across the cell membrane with the help of transport proteins. a. Each transport protein imbedded in the cell membrane is specific to a certain type of molecule that it will let into or out of the cell.

IV. Active Transport

A. Active transport is the movement of particles across the cell membrane

(into or out of the cell) against the concentration ([ ]) gradient.1. Against the concentration gradient means from low to

high concentration.

Active Transport

Picture 3: Cell Membrane

2. This means that the particles move from an area of where there is a 1 to 1 ratio of something to where there is a lot of that same thing until there are the correct amounts on both sides of the membrane.

3. Active transport does require energy in the form of ATP in order to occur—in fact, 30-40% of all the energy that your body uses is used for cellular

transport.

B. Types of Active Transport

1. Transporter Protein Mediated (helped): this type of AT uses special transport proteins to move particles against the concentration gradient. a. When you use your model to demonstrate this, you have to physically move the transporter protein (think: this requires energy)

2. Endocytosis and Exocytosis: these types of transport are called Bulk Transport

Endocytosis:(into the cell)

Exocytosis:(out of the cell)