Cell Membrane Notes. Make up of the Cell Membrane Phospholipid bilayer - Two layers of charged lipids face each other, Only small particles with no charge.

Cell Membrane Notes

Make up of the Cell Membrane

• Phospholipid bilayer - Two layers of charged lipids face each other,

Only small particles with no charge can pass through

• Proteins - Move material through the membrane that can’t pass between lipids

• Carbohydrates - Identify the cell

Make up of the Cell Membrane (cont)

• Cholesterol - Holds phospholipids together

Selective Permeability

• Permeable – allows things to pass through• Selectively Permeable – only certain things

can pass through• Only small molecules can fit between the

phospholipids.• The polar heads of the phospholipids

prevent charged molecules from passing between them.

• Proteins help certain larger molecules to enter

• Diffusion – particles move from an area of high concentration to low concentration in other words: particles spread out

http://www.biologycorner.com/bio1/diffusion.html

Movement Across the Membrane

Concentration – the ratio of the amount of a substance in a solution to the amount of water

Isotonic – iso = same, tonic = strength, concentrationA solution in which the concentration is the same outside the cell as inside

Water will flow into and out of the cell equally.The cell will stay the same.

Solutions

Hypotonic – hypo = belowA solution in which the concentration is

lower outside the cell than inside

Water will flow into the cell to even out the concentration.

The cell will expand.

Hypertonic – hyper = aboveA solution in which the concentration is

higher outside the cell than inside.

Water will flow out of the cell to even out the concentration.

The cell will shrink.

http://www.northland.cc.mn.us/biology/Biology1111/animations/passive1.html

Methods of transport

• Osmosis – – Water flows between the lipids from an

area of high concentration to low concentration

– No energy is required

• Diffusion – – Small, uncharged particles move

between the lipids– from an area of high concentration to

low concentration– this does not require energy

– Particles such as CO2, and O2

• Facilitated Diffusion / Passive Transport – – Transport (carrier) proteins allow large

particles to flow through the membrane– with the concentration gradient (from

high concentration to low concentration)– This does not require energy– Particles that are too

large to fit between lipids: such as glucose

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

• Active Transport – – Transport proteins (ion pumps) pump

ions and other particles – against the concentration gradient (from

low concentration to high concentration)– This requires energy– Particles such as Na + (sodium ion) and

K+ (potassium ion)– http://highered.mcgraw-hill.com/sites/0072495855/

student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

Endocytosis (pinocytosis or phagocytosis)

• The cell membrane surrounds and engulfs a large particle from outside the cell.

• The particle is then enclosed in a membrane

• Requires energy • Particles such as food, proteins, or

large amounts of water.

Exocytosis• The opposite of endocytosis• A membrane filled with particles fuses with

the cell membrane to release particles from the cell

• Cell removes waste or sends out proteins

• Requires energy

• http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter6/animations.html#