05CellMembranes

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Cell Membranes & Movement Across Them : 

2006-2007 Cell Membranes & Movement Across Them

Cell (plasma) membrane: 

Cell (plasma) membrane Cells need an inside & an outside… separate cell from its environment cell membrane is the boundary IN food - sugars - proteins - fats salts O 2 H 2 O OUT waste - ammonia - salts - CO 2 - H 2 O products - proteins cell needs materials in & products or waste out

Building a membrane: 

Building a membrane How do you build a barrier that keeps the watery contents of the cell separate from the watery environment? What substance do you know that doesn ’ t mix with water?  FATS   LIPIDS  Remember: oil & water don ’ t mix!!

Lipids of cell membrane: 

Lipids of cell membrane Membrane is made of special kind of lipid phospholipids “ split personality ” Membrane is a double layer phospholipid bilayer inside cell outside cell lipid “ repelled by water ” “ attracted to water ” phosphate

Semi-permeable membrane: 

Semi-permeable membrane Cell membrane controls what gets in or out Need to allow some materials — but not all — to pass through the membrane semi-permeable only some material can get in or out aa H 2 O sugar lipids salt waste So what needs to get across the membrane? O 2

Crossing the cell membrane: 

Crossing the cell membrane What molecules can get through the cell membrane directly? fats and oils can pass directly through inside cell outside cell lipid salt aa H 2 O sugar waste but… what about other stuff?

Cell membrane channels: 

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

How do you build a semi-permeable cell membrane?: 

How do you build a semi-permeable cell membrane? Channels are made of proteins proteins both “ like ” water & “ like ” lipids bi-lipid membrane protein channels in bi-lipid membrane

Protein channels: 

Protein channels Proteins act as doors in the membrane channels to move specific molecules through cell membrane HIGH LOW

Movement through the channel: 

Movement through the channel Why do molecules move through membrane if you give them a channel? ? ? HIGH LOW

Molecules move from high to low: 

Molecules move from high to low Diffusion move from HIGH to LOW concentration

Diffusion: 

Diffusion Move from HIGH to LOW concentration passive transport no energy needed diffusion osmosis diffusion of water

Simple Diffusion : 

Simple Diffusion Move from HIGH to LOW inside cell outside cell Which way will fat move? fat fat fat fat fat fat fat fat fat fat fat fat fat fat LOW HIGH

Facilitated Diffusion: 

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

Diffusion: 

Diffusion Move from HIGH to LOW concentration directly through membrane simple diffusion no energy needed help through a protein channel facilitated diffusion (with help) no energy needed HIGH LOW

Simple vs. facilitated diffusion: 

Simple vs. facilitated diffusion inside cell outside cell lipid inside cell outside cell H 2 O simple diffusion facilitated diffusion H 2 O protein channel

Active transport: 

Active transport Cells may need molecules to move against concentration “ hill ” need to pump “ uphill ” from LOW to HIGH using energy protein pump requires energy ATP ATP

Transport summary: 

Transport summary simple diffusion facilitated diffusion active transport ATP

Osmosis Movement of Water Across Cell Membrane : 

2006-2007 Osmosis Movement of Water Across Cell Membrane

Osmosis: 

Osmosis Water is very important, so we talk about water separately Osmosis diffusion of water from HIGH concentration of water to LOW concentration of water across a semi-permeable membrane

Ice Fishing in Barrow: 

Ice Fishing in Barrow