Life’s Guardian…

Cell Membranes…their Structure & Function

How do things enter and leave living cells?

How does oxygen get into our cells?

How does carbon dioxide and other waste products leave our cells?

How do nutrients enter our cells?How do white blood cells

engulf foreign invaders?

Do cells drink and eat?

All living cells are surrounded by an extracellular fluid (ECF).

SMALL HYDROPHOBIC

MOLECULESO2 , CO2 , N2 ,

benzene

SMALL UNCHARGED POLAR MOLECULES

LARGER UNCHARGED POLAR MOLECULES

amino acids, glucose, nucleotides

H2O , alcohols

N+ , Na+ , HCO 3- , K+, Ca2+ , Cl - , Mg 2+

IONS

Besides other organisms, there are many chemicals in the ECF.

Solutions where the water is the solvent such as the ECF and blood

are called aqueous solutions.

Solution

solvent

Solution

solvent

A solution is a combination of a solvent with one or more solutes.

solute

If this solution was blood the solvent would be called plasma and the solute

would be red and white blood cells.

An organism's chemical processes are carried out inside cells and/or it’s

organelles.

Biochemical reactions require raw materials from outside the cell and

generate waste products inside that the cell must discharge back into its

environment.

In order to do this and remain alive a cell must maintain

CHEMICAL HOMEOSTASIS.

Homeostasis is the maintenance of a steady state or balance within the cell

or organism.

The PLASMA MEMBRANE plays a major role in the maintenance of

homeostasis as it determines what enters and leaves the cell.

Life’s Hangout Plasma membrane

Embedded Proteins

Phospholipids

Life’s Hangout Phospholipids hydrophillic or

water loving head

hydrophobic or water fearing end

Gk: phil – loving phob – fear

~75-95% of the cell’s plasma membrane

Life’s Hangout Embedded Proteins

Carrier proteins that regulate transport and diffusion

Marker proteins that identify the cell to other cells

And receptor proteins that allow the cell to receive instructions

~5-25% of the cell’s plasma membrane

Life’s Hangout Embedded Proteins

Diffusion

Embedded proteins provide the cell with a pore for the passive transport of solute particles.

concentrationgradient

Life’s Hangout

Carrier proteins provide the cell with a means of active transport.

Embedded Proteins

facilitated diffusion

concentrationgradient

Life’s Hangout Embedded Proteins

Symport carrier proteins provide the cell with a means of two-way diffusion.

Sodium-Na+

Glucose

Active Transport

ATPconcentrationgradient

Life’s Hangout

Marker proteins extend across the plasma membrane and serve to identify the cell. The immune system uses these proteins to tell friendly cells from foreign invaders.

Embedded Proteins

Life’s Hangout

Receptor proteins are used in intercellular communication. In this animation a hormone binds to the

receptor. This causes the receptor protein to release a chemical signal toperform a specific

action.

Embedded Proteins

Life’s Hangout Embedded Proteins

The passive transport of solvent molecules like water is called ….

concentrationgradient

A

B

Life’s Hangout Review

Cells are essentially a selectively permeable sack of particles dissolved in water with larger complex structures suspended in the resulting solution.

For this reason, it is important to know what a solution is before attempting to understand how cells respond to changes in their environments.

Simple Diffusion