Cell Membarane• Also known as

Plasma Membrane and Phospholipid Bi-layer

• Defines the shape of the cell.

• Maintains Homeostasis (controls what goes in and out)

What is the cell membrane made of?

• Phosphate Head- Polar so always points toward water (Hydrophilic)

• Lipid Tails- Non-polar so always

point away from water (Hydrophobic)

(Blood)

(Cytoplasm)

1. Channel Protein- tunnel in and out. Can be gated to open and close. Use energy to go against concentration (active transport) and do not use energy to go with concentration (passive transport)

2. Receptor Protein- receives chemical signals from the blood and communicates them to the inside of the cell.

3. Glycoprotein + Carbohydrate- identifies the cell so it will not be destroyed.

Key Words

• Solution- combination of a solute and a solvent.

• Solute- Substance that is dissolved in a solvent (i.e. salt, sugar etc)

• Solvent- Substance that other substances are dissolved into (i.e.- water)

• Concentration Gradient- Difference in solute concentration from one side of the membrane compared to the other.

Diffusion• Movement of a solute within a solvent from

high concentration to low concentration• EXAMPLE- Food coloring (Solute) moving from

the high concentration of a drop to the low concentration of the water (Solvent).

Osmosis• Diffusion of water through a semi-permeable

membrane• Water is the only substance that can move

freely in an out of cells without using channel proteins.

More Complicated Than That

Why Water Moves

• Hypertonic Solution- The outside of the cell has more solute than inside the cell

• RESULT- Water moves out and the cell shrinks.

Why Water Moves

• Hypotonic Solution- The outside of the cell has less solute than inside the cell.

• RESULT- Water moves in and the cell swells/bursts.

Why Water Moves

• Isotonic Solution- When there is an equal amount of solute inside and outside the cell

• RESULT- Water moves both in and out of the cell at the same rate and the cell stays the same

Moving Stuff

Passive Transport- Movement across a cell membrane that goes with concentration gradient and does not use any energy

Examples- Osmosis and Facilitated Diffusion

Moving Things

• Active Transport- Movement across a membrane going against concentration gradient where energy is needed

• Examples- Endocytosis and Exocytosis

Endocytosis- use of vesicles to transport large objects into the cell.

Exocytosis-use of vesicles to move large objects out of the cell.

Sodium Potassium PumpActive Transport

• Sodium Potassium Pump moves 3 Na+ ions out of the cell and brings 2 K+ ions into the cell creating + out side and a – inside.

• This is moving against concentration so it requires ATP (Energy)

• When the nerve fires Na+ ion channels open in the membrane and Na+ floods in changing charge on the inside only to be reset by the Na/K pump.

https://www.youtube.com/watch?v=P-imDC1txWw&index=2&list=FLEezLUm-pa3vfMmQGp1aPTQ

https://www.youtube.com/watch?v=SdUUP2pMmQ4&index=1&list=FLEezLUm-pa3vfMmQGp1aPTQ