Opening Questions:Opening Questions:1. What is the 11. What is the 1stst major part of major part of the cell we talked about?the cell we talked about?

2. Name one thing that it does 2. Name one thing that it does for the cell.for the cell.

3. Name the three types of 3. Name the three types of proteins that make up the proteins that make up the Cytoskeleton.Cytoskeleton.

Learning OutcomesLearning OutcomesRecognize the key components Recognize the key components of the cell plasma membrane.of the cell plasma membrane.Explain how the plasma Explain how the plasma membrane regulates the membrane regulates the passage f molecules into and out passage f molecules into and out of the cell.of the cell.Describe the diverse functions of Describe the diverse functions of proteins embedded in the palsma proteins embedded in the palsma membrane.membrane.

The Three Major The Three Major Parts of the CellParts of the Cell

2. PLASMA CELL MEMBRANE

• It is the protective outer covering of all cells

• It gives the cell its distinct shape

• Acts as a fence around the cell

• Its like a PICKET FENCE

• Must stay in a SEMI-FLUID state in order to be

• SEMI-PERMEABLE or SELECTIVELY PERMEABLE

SELECTIVELY or SEMI-PERMEABLE• 1. Allows certain substances in• Example---Nutrients• 2. Allows certain substances out• Example----Waste• 3. Keeps certain things in• Example----Organelles• 4. Keeps certain things out• Example---Disease and foreign

objects

A. 3 Molecules of the Cell Membrane

1. PHOSPHOLIPID MOLECULE• Has a head that is made of

phosphate• “Hydrophillic”• Water loving

• Because it can dissolve in water

• It has a tail that is made up of a lipid

• “Hydrophobic”• Water fearing

• Because it does not dissolve in water

• Lipids will dissolve in other lipids

• Because the tail is afraid of H2O and there is H2O surrounding your cells….

• Extracellular fluid outside each cell and

• The cytoplasm (made of water and various molecules) in each cell

• How do the phospholipid molecules line up?

• They form a DOUBLE layer with the tails facing each other and the heads on the outside and inside.

• Phospholipid molecules act as the pickets of the fence

• Little molecules can pass through them by dissolving in lipids.

2. PROTEINSProteins are used to identify large molecules or molecules that can not dissolve in lipids.

Proteins decide whether the larger molecules can come in or not

2 TYPES OF PROTEINS:

1. Integral Proteins----Proteins that go all the way

through the membrane

2. Peripheral Proteins---Proteins that are only on one side

of the membrane

Proteins act as the gate of the fence

MEMBRANE PROTEINSa. Channel Proteinsb. Transport Proteinsc. Cell Recognition Proteins

d. Receptor Proteinse. Enzymatic Proteinsf. Junction Proteins

A. CHANNEL PROTEINS

Channel Proteins form a tunnel across the entire membrane…

They allow only one or a few specific types of molecules to enter or exit the cell.

EXAMPLEAquaporins---Channel proteins in the kidney…

Allows water molecules in or out of the cell

Without them we would dehydrate

B. TRANSPORT PROTEINSTransport Proteins often bond with a molecule or ion and help carry across the membrane.

They usually use cell energy to help the molecule/ion across

EXAMPLEThey help sodium and potassium to cross the membrane of the nerve cell (neuron)

Without them, nerve impulses would be impossible.

C. CELL RECOGNITION

PROTEINSCell Recognition Proteins are glycoproteins that are used to enable our bodies to distinguish between our own cells and that of another organism.

MORE INFOFound especially on white blood cells

Allow them to distinguish between the pathogens that invade our body and our own cells

D. RECEPTOR PROTEINS

Receptor Proteins are proteins that change their shape along the membrane which allows a molecule known as a SIGNAL MOLECULE to bind to it.

The bonding of a signal molecule causes the receptor protein to change shape.

When the receptor protein changes shape the cell is able to respond to a certain molecule.

EXAMPLEHormone insulin binds to the receptor proteins in liver cells.

When they bind to the membrane they allow the liver cells to store glucose.

E. ENZYMATIC PROTEINS

Enzymatic Proteins are proteins that are directly involved in the metabolic processes of the cell.

These proteins can attach to various cell membranes

EXAMPLEDNA helicase---Enzyme that causes DNA to unzip (break apart) so it can replicate (duplicate)

F. JUNCTION PROTEINS

Junction Proteins are proteins will be discussed later.

But they assist in cell to cell adhesion and communication

MORE INFOThe cells in the bladder use junction proteins to adhere to one another when the bladder fills with liquid waste (urine).

3. CHOLESTEROL• Another lipid

• Helps to give the cell membrane its shape

Cholesterol acts as the posts of the fence

3 major molecules(REVIEW)

• 1. PhosphoLIPID—

• Pickets—small things in & out

• 2. Proteins---

• Gates---lets big things in & out

• 3. Cholesterol---LIPID

• Posts---structure

• The cell membrane is considered a bilayer or a

DOUBLE layer of

• PROTEINS and

• LIPIDS

• Scientists way of describing the cell

membrane• The

Fluid Mosaic

Model

• FLUID---Because the membrane must stay semi-

fluid to be selectively permeable

• MOSAIC---Because it is made up of many different

molecules but is one structure

Wrap It Up

• The plasma cell membrane is used as protection for each cell--give it distinct shape

• It stays semi fluid---allowing it to be selectively permeable

• This means it selects what goes in and out and

• what stays in and out

• The plasma membrane is made up of 3 main molecules:

• Phospholipid molecules

• Protein molecules and

• Cholesterol molecules

• For this reason the plasma (cell) membrane is considered a DOUBLE layer of PROTEINS and LIPIDS.