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Phospholipid Bilayer
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Cell MembranesOsmosis and Diffusion
Functions of Membranes1. Protect cell2. Control incoming and outgoing substances3. Maintain ion concentrations of various
substances4. Selectively permeable - allows some
molecules in, others are kept out
Phospholipid Bilayer
Fluid Mosaic Model
Solutions• Solutions are made of solute and a solvent
• Solvent - the liquid into which the solute is poured and dissolved. We will use water as our solvent today.
• Solute - substance that is dissolved or put into the solvent. Salt and sucrose are solutes.
Methods of Transport Across Membranes
1. Diffusion -passive transport - no energy expended
2. Osmosis - Passive transport of water across membrane
3. Facilitated Diffusion - Use of proteins to carry polar molecules or ions across
4. Active Transport- requires energy to transportmolecules against a concentration gradient – energy is in the form of ATP
Diffusion
• Movement of molecules from an area of high concentration to an area of low concentration.
• Movement from one side of a membrane to another, un-facilitated
Diffusion
Osmosis
Tonicity is a relative term• Hypotonic SolutionHypotonic Solution - One solution has a
lower concentration of solute than another.
• Hypertonic SolutionHypertonic Solution - one solution has a higher concentration of solute than another.
• Isotonic SolutionIsotonic Solution - both solutions have same concentrations of solute.
Plant and Animal Cells put into various solutions
Types of Transport
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