Crazy scientist Says…

*Answer the following questions in complete sentences.

How is a window screen similar to a cell membrane? Answer the following in your response:– What are some things that can pass through a

window screen?– What are some things that cannot pass through a

window screen?– Why is it important to keep these things from

moving through the screen?– The cell is surrounded by a cell membrane, which

regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of the cell

Life is Cellular

Cell Boundaries

Cell Membrane• The Cell Membrane is made up of a

lipid bilayer.• It has two functions:

1. Regulates what enters and leaves the cell. This is called SELECTIVE PERMEABILITY.

2. Provides support and protection.

Permeate

• To spread, or pass through

Selective Permeability• SELECTIVE PERMEABILITY is caused

by the way PHOSPHOLIPIDS in the cell membrane interact with water:– Phospholipid (lipid) has a polar “head”

on the outside (likes water - hydrophilic) and two (fatty acids) nonpolar “tails” on the inside (hates water - hydrophobic).

PHOSPHATE GROUP

2 FATTY ACIDS

Selective Permeability Cont…

• SELECTIVE PERMEABILITY is also caused by the MEMBRANE PROTEINS in the lipid bilayer.

• Substances can move in and out of the cell by traveling through these proteins.– Kind of like a tunnel or gate

Cell Communication

• Cells must communicate with each other!•Nutrition - Feed Me

- Need for nutrients to run efficiently. •Hormone Regulator - Regulate Me- Regulate temperature, metabolism. •Cleansing/Excretion - Cleanse Me- Need for excretion of waste/toxins. •Host Defense - Repair Me- Need for damage repair and renewal.•Defense Cell - Defend Me- Need for help from specialized defense cells, i.e. white blood cells.•Identification - See Me- Cells communicate such things as their structure, location and function e.g. "I'm a liver cell, and here's what I do."

Cell Communication Cont…

• Cells that do not lie next to each other cannot communicate directly.

• Signal molecules are released to carry information to nearby cells.

• MEMBRANE PROTEINS help communication between cells and carry substances in and out of the cell:– Peripheral proteins – sit on the surface

of the membrane. (many)– Integral proteins – cross through the

membrane…hard workers! (few)

Types of Membrane Proteins

• MARKER PROTEINS:– Go through the cell membrane and serve to

identify the cell they occupy. – The immune system uses these proteins to tell

friendly cells from foreign invaders. – They are as unique as fingerprints. – They play an important role in organ

transplants. If the marker proteins on a transplanted organ are different from those of the original organ the body will reject it as a foreign invader.

Types of Membrane Proteins Cont…

• RECEPTOR PROTEINS:– These proteins are used for

communication in the cell – allows cells to communicate.

– The receptor protein releases a signal to perform some action – muscle contraction.

Types of Membrane Proteins Cont…

• TRANSPORT PROTEINS: regulates what enters or leaves the cell.

1. CARRIER PROTEINS do not extend all the way through the membrane. They move specific molecules through the membrane one at a time.

2. CHANNEL PROTEINS extend through the lipid bilayer. They form a pore through the membrane that can move molecules in several ways.

Other “Stuff” in the Membrane

• CHOLESTEROL:– Steroids are sometimes a component of

cell membranes in the form of cholesterol. When it is present it reduces the fluidity of the membrane. Not all membranes contain cholesterol.

Cell Transport

• The cell membrane has to regulate the movement of molecules from one side of the membrane to the other.

• Molecules move by:– Passive Transport – no energy required– Active Transport – energy required– Endocytosis– Exocytosis

Cell Transport Cont…

• Passive Transport – diffusion of molecules without the use of energy.

Cell Transport Passive & Active Transport

• Facilitated diffusion (no energy) – glucose molecules cannot diffuse across the membrane on their own. Carrier proteins move glucose molecules through protein channels.

Cell Transport• Hypertonic –

water diffuses OUT of the cell (cell shrinks).

• Hypotonic – water diffuses INTO the cell (cell swells).

• Isotonic – water diffuses into and out of the cell at EQUAL rates (cell stays the same).

Cell Transport Cont…• Active Transport

– the diffusion of molecules with the use of energy.– Sodium

Potassium Pump – most important membrane pumps in animal cells. Carrier protein carries 3 Na out and 2 K in.

– ATP is the energy needed to move molecules against their concentration gradient.

Cell Transport Cont…

• Endocytosis – taking in material by pockets of the cell membrane (vesicles).– Phagocytosis –

white blood cell eating bacteria.

• Exocytosis – releasing large amounts of material (vesicle).

Bio I• For your OUTPUT you will be

recreating the following types of transport:– Passive– Active– Diffusion– Osmosis– Facilitated diffusion– Hypertonic solution– Hypotonic solution– Isotonic solution