the plasma membrane section 7.2 p.175-178. maintaining a balance all living cells must maintain a...

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The Plasma Membrane Section 7.2 p.175-178

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Page 1: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

The Plasma MembraneSection 7.2p.175-178

Page 2: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

Maintaining a Balance• All living cells must maintain a balance

regardless of internal + external conditions• Survival depends on the cell’s ability to

maintain proper conditions within itself

Page 3: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

Why cells must control materials• Cells need nutrients

to function– Glucose– Amino acids– Lipids

• Must enter through the plasma membrane– The flexible boundary

between the cell + its environment

Page 4: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

Why cells must control materials• Substances such as wastes + products must

leave through the plasma membrane– Substances enter + leave to maintain homeostasis– Selectively permeable• Ability to allow some molecule to pass through while

keeping others out– Examples

» Water vs. Na+ ions

Page 5: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

Selectively Permeable

Page 6: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

Structure of the Plasma Membrane

• Recall – LIPIDS (Fatty Acids + glycerol)

• Phospholipid– Two fatty acids, glycerol, + a

phosphate group• Plasma membrane is

composed of a phospholipid bilayer

Page 7: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

The Phospholipid bilayer• Fatty acids “tails” are hydrophobic

– Don’t want to interact with water• Phosphate group “head” is hydrophilic

– Wants to interact with water

• Creates a barrier that regulates the ease in which substances cross the plasma membrane

Page 8: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

Fluid Mosaic Model• The proteins embedded in the bilayer create the

“mosaic”• The phospholipids move within the membrane

(like a fluid)

Page 9: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

Other components of the P.M.• Cholesterol– Helps to stabilize the phospholipids by preventing

their FA’s from sticking together

Page 10: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

Other components of the P.M.• Proteins

– Transport• Move substances through PM

– Markers• Identify chemical signals + each other

– Inner surface• Gives cell’s structure flexibility

Page 11: The Plasma Membrane Section 7.2 p.175-178. Maintaining a Balance All living cells must maintain a balance regardless of internal + external conditions

A video clip….

• Plasma Membrane