Welcome Back!• Current Event?• 4.2 Bellringer• Film advertisements• Membranes (10:40)• Work on HW or finishing filming (time

permitting)

• HW: Draw a representation of a membrane, showing all parts. NOTE that we no longer have time to build one – so ignore the building instructions

Membranes

PLASMA MEMBRANE- keeping it all together

• Isolates the cell from external world• Regulates entry and exit to the cell

• Made up of phospholipids

• The 2 layers of phospholipid molecules are called the phospholipid bilayer

Phosphate

Fatty acid tails

1 phospholipid

Plasma membrane• Called a fluid mosaic because of the different

parts AND b/c phospholipids move around.

Phospholipid “Sandwich”• phosphates touch

watery sides (“the bread”)

• The fatty acids (lipids) “hide” creating the inside of the PM.

phosphate

fatty acids

You are Watery

• The fluid that surrounds all cells in body (interstitial fluid) AND the cytoplasm is:• mostly water• with• salts, proteins, lipids, carbohydrates,

sugars, amino acids, nucleotides, dissolved into it

• Ex: Think liquid in a blister or tears or sweat

Cytoplasm

• Made of:• Function:

–Location of most of the cells metabolic activities (aka: the biochemical reactions that support life)

–Gives cell “fullness”

Define: Mosaic• Mosaic is the art of creating images with an

assemblage of small pieces of colored glass, stone, or other materials

• For example Snowflake Mosaic!

•Other parts of the “mosaic” are…–Proteins do a whole host of things–Cholesterol acts as a stabilizer

Protein Functions

1. Transport

• Move molecules in or out of the cell that can’t cross the membrane

2. Signal Reception

• E.g. receives signals from hormones

• Cell can change activity or gene expression

3. Identifier

• E.g. type A or B blood

• Body can know what cell it is and not to attack it

Blood Transfusions Gone Wrong

4. Cell Connections

• Connect cell to cytoskeleton (interior side)

• Connect cell to other cells (exterior side)

Your Task

• Build a model of the cell membrane out of materials of your choosing

• Think of things you have lying around or waste products (e.g. toilet paper tubes)

• Must include:– Phospholipid bilayer– 4 types of membrane proteins– Labels

• 3D preferred

New Task

• Draw a representation of the membrane

• Include all parts you were supposed to construct and label

Way Super Fancy Example

Phospholipid Head

Phospholipid Tail

Protein

Bring Materials for Friday

•Most of Friday to Build•Due Tuesday