Transport through the

Cell Membrane

Fluid Mosaic Model

The Cell Membrane is Semi-permeable

SOME MOLECULES CAN GET THROUGH

Very small or Non-charged (nonpolar)

Passive Transport

Does not expend cellular energy for the movement to take place

Ex-rolling down a hill

3 types:1. Diffusion2. Osmosis3. Facilitated Diffusion

I. DIFFUSION:Definition:

Transport of molecules (in general)From an area of higher concentration to an area of lower concentrationUntil equal distribution of concentrations reached in all areas (EQUILIBRIUM)Due to the random movement of molecules

Conceptual Diagram:

Example:If you had glucose molecules and starch molecules, which ones do you think could get through after 24 hours and why? The membrane is permeable to both.

4% C6H12O6

in H2O

15% NaCl2% C6H12O6

15 % NaCl2% C6H12O6

30% NaCl

in H2O

Definitions

Solute: what gets dissolved

Solvent: What does the dissolving, more plentiful that solute

Solution: the mixture of solutes and solvent

Example: H2O and NaClSolute: NaClSolvent: H2O

Solution: H2O and NaCl

II. OSMOSIS:Definition:

Diffusion (movement) of H2Ofrom to high to low concentrationTHROUGH A MEMBRANEuntil equilibrium

II. OSMOSIS:

II. OSMOSIS:

U-tube Osmosis

How do you get different concentrations of water (2 ways)?

**FIX IN YOUR NOTE TEMPLATE

1.Change the amount of solute or solvent.

2.Add a membrane

3 Types of Solutions (outside of cell):1. Hypertonic2. Hypotonic3. Isotonic

1.Hypertonic:

MOREMore solute, less solvent (H2O)

90% water

80% water

2. Hypotonic:

LESSLess solute, more solvent

3. Isotonic:

EQUALEqual amounts of solute/solvent concentrations on both sides of membrane

(a) Isotonic

Water concentration inside the cells is equal to the water concentration in the fluid surrounding the cell. Therefore, there is no net movement of water either into or out of the cell.

(b) Hypertonic

Water concentration in the surrounding medium is lower than it is in the cell. Water moves out of the cells and the cells shrivel (crenate).

(c) Hypotonic

Water concentration outside the cell is greater than it is inside the cell. Water moves into the cell, which swell and sometimes burst – a process called lysis.

Consequences:

Hypertonic PLASMOLYSIS (cell shrinking)

Examples:Drinking out of ocean when you are dying of thirst orPlacing a fresh water fish in salt water…

Consequences:

(a) Isotonic

Water concentration inside the cells is equal to the water concentration in the fluid surrounding the cell. Therefore, there is no net movement of water either into or out of the cell.

(b) Hypertonic

Water concentration in the surrounding medium is lower than it is in the cell. Water moves out of the cells and the cells shrivel (crenate).

(c) Hypotonic

Water concentration outside the cell is greater than it is inside the cell. Water moves into the cell, which swell and sometimes burst – a process called lysis.

Consequences:

Hypotonic Cytolysis (cell bursting)

Examples: Place a salt water fish in fresh water Red Blood Cells in pure water

Turgor Pressure = Osmotic Pressure

As a result of osmosis, extra water molecules accumulate on one side of membrane and cause pressure on the membrane

“Turgor”

Example:

water

III. FACILITATIVE DIFFUSION:

Protein Channels in the cell membrane accept only specific particles, like a lock accepts a particular key.

III. FACILITATIVE DIFFUSION:

III. FACILITATIVE DIFFUSION:

Many of these protein channels are “two-way” and are called PORES.These transport molecules ions or molecules (solutes) through membranes in either direction

III. FACILITATIVE DIFFUSION:

Like an open door allows you to pass into or out of a room.

Different solute particles fit different pores

This depends on

Size

Polarity

Shape of molecule

Ex. Glucose

III. FACILITATIVE DIFFUSION:

When a solute that is plentiful on one side of membrane,

they will pass by diffusion toward other side with the lower concentration.

Until concentration becomes equal on both sides

DON’T FORGET, THESE WERE ALL

PASSIVE TRANSPORT –SO THE CELL DID NOT NEED TO EXPEND ANY NRG TO MAKE IT HAPPEN!!!!!