Cell Membranes Movement Across Them Regents Biology 2006

Cell Membranes & Movement Across Them Regents Biology 2006 -2007

Lipids of cell membrane § Membrane is made of special kind of lipid u u phospholipids “split personality” “attracted to water” § Membrane is a double layer § Membrane is semi-permeable Hydrophilic phosphate inside cell Fatty acid Hydrophobic outside cell Regents Biology “repelled by water”

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Passive Transport – No Energy § Diffusion § Osmosis § Facilitated Diffusion Regents Biology

Molecules move from high to low § Diffusion u move from HIGH to LOW concentration Regents Biology

Diffusion § Move from HIGH to LOW concentration passive transport u no energy needed u EXAMPLE u Regents Biology diffusion

Crossing the cell membrane § What molecules can get through the cell membrane directly? u Oxygen, fats and oils can pass directly through inside cell waste outside cell Regents Biology lipid sugar aa salt but… what about other stuff?

Cell membrane channels § Need to make “doors” through membrane u protein channels allow substances in & out § specific channels allow specific material in & out § H 2 O channel, salt channel, sugar channel, etc. inside cell salt waste. Biology Regents H 2 O aa sugar outside cell

Facilitated Diffusion § Move from HIGH to LOW through a channel sugar inside cell sugar LOW Which way will sugar move? HIGH outside cell sugar Regents Biologysugar sugar

Simple vs. facilitated diffusion simple diffusion inside cell O 2 facilitated diffusion inside cell sugar protein channel outside cell Regents Biology outside cell sugar

Osmosis Water is very important, so we talk about water separately diffusion of water Regents Biology

Osmosis § Osmosis u diffusion of water from HIGH concentration of water to LOW concentration of water § across a semi-permeable membrane Regents Biology

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Active transport § Cells may need molecules to move from LOW to HIGH concentration u requires energy (ATP) Regents Biology ATP

ANALOGY: ENERGY NEEDED: Active Transport NO ENERGY NEEDED: Diffusion Osmosis Facilitated Diffusion Regents Biology

• Endocytosis and Exocytosis is how very large molecules (such as food, wastes and some protiens) get into and out of the cell Food is moved into the cell by Endocytosis Wastes are moved out of the cell by Exocytosis animation Regents Biology

Cystic Fibrosis § CFTR Protein § Mutations in the DNA u u Doesn’t make it to membrane Channel won’t open How is homeostasis affected? Cystic Fibrosis Video (5: 08 -6: 32) Regents Biology