Post on 27-Dec-2015
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Cell Membrane
• Cell membrane regulates what leaves and enters the cell.
• It is a lipid bilayer with proteins embedded in the layer.
Phospholipids
• Phosphate head- polar “likes” water• Lipid tail- 2 fatty acids- non-polar- does not
“like” water
Phospolipid Bilayer
• There are 2 types of proteins in the lipid bilayer– Integral Proteins- transport substances across
membrane– Peripheral Proteins- bind to the bilayer
temporarily, perform various cellular processes.
Phospholipid Bilayer
• Cholesterol plays an important role in maintaining the integrity of the membrane. – Keeps it firm and from becoming too
permeable.• Carbohydrates- Act as cell markers, allow
cells to identify each other.
Cell Membrane Video
• http://www.youtube.com/watch?v=moPJkCbKjBs
Diffusion
• All cells must exist in a liquid environment in order to survive.
• A solution is a mixture of two or more substances.
• Solute- substance dissolved into the solvent
• Solvent- substance solute dissolves into.– Ex- iced tea mix is the solute, water is the
solvent
Diffusion
• Particles are constantly moving in a solution.
• Particles tend to move from an area of high concentration to an area of low concentration, this is called diffusion.
• Movement from high to low concentration is called the concentration gradient
Equilibrium
• Particles move from high to low conc. until they are the same throughout the system, this is called equilibrium
Diffusion
• Since particle movement is random, diffusion occurs across the membrane without the use of energy.– Called Passive Diffusion
Osmosis
• Water will move across a membrane until the concentrations of water and the solute are equal, this is an isotonic solution.
• Hypertonic solution- when there is more solute then water. concentrated
• Hypotonic solution- when there is more water then solute. dilute
Facilitated Diffusion
• Proteins in the cell membrane allow some substances pass through easier then others.
• Still follows concentration gradient• Ex- doorman at a club, lets some people in
easier then others
Active Transport
• Sometimes particles have to move from low to high concentration, against the concentration gradient.
• This requires energy and is called active transport.
• Ex- swimming against the current of a river.
• Use proteins to carry particles across
Endocytosis and Exocytosis
• Particles that are too large to pass through the membrane other ways
• Endocytosis- the cell membrane folds around an object and envelops it.
Endocytosis and exocytosis
• 2 types of endocytosis–Phagocytosis- used for taking in
food particles–Pinocytosis- used for taking in
liquids