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 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, concentration A 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 = below A 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 = above A 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.

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 CO 2, and O 2

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 hill.com/sites/ /student_view0/chapter2/animation__how_facilitated_di ffusion_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) – hill.com/sites/ /student_view0/chapter2/animation__how_the _sodium_potassium_pump_works.htmlhttp://highered.mcgraw- hill.com/sites/ /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

hill.com/sites/ /student_view0/ chapter6/animations.html# hill.com/sites/ /student_view0/ chapter6/animations.html#