Plasma Membrane Plasma Membrane AKA Cell Membrane What
Plasma Membrane
Plasma Membrane (AKA Cell Membrane) • What is the plasma membrane? • What does it do? • What is its composition?
• Plasma membrane = the flexible boundary between the cell and its environment • • Allows: Things in the cell Things out of the cell Maintains BALANCE in the cell
• What is maintaining balance in the cell called? • Homeostasis!
How does the plasma membrane maintain homeostasis? • Plasma membranes are selectively permeable • Selective permeability = process in which a membrane allows some molecules to pass while keeping others in/out.
Plasma membranes are regulators…
How is a screened window similar to a cell membrane?
Plasma Membrane Structure
Structure is the KEY! • The specific structure of the plasma membrane allows it to be selectively permeable
Plasma Membrane Structures: • Thin layer of phosopholipds, proteins, and cholesterol • Phospholipid = kind of lipid found in the cell membrane – Glycerol, 2 fatty acids, and phosphate (PO 4) – Phospholipids have 2 parts
Each part has a different property in water! 1. Phosphate Head – Hydrophilic – Can dissolve in water 2. Lipid tails (x 2) – Hydrophobic – Cannot dissolve in water
What does the polarity mean about the passage of water in/out of the cell? • Water CAN pass through the polar part, but CANNOT pass through the nonpolar part. • This allows the cell to prevent water loss and prevent “drowning”
• Cell membranes consist of 2 phospholipid layers called a bilayer (think bicycle has 2 wheels)
Plasma Membrane • Made of: phospholipid bilayer – Phosphate head hydrophilic – Lipid tail hydrophobic – Carrier proteins – Cholesterol (good kind) • Called the fluid mosaic model – Moves fluidly – Mosaic of proteins scattered in membrane – http: //www. youtube. com/watch? v=Qqsf_UJcf. Bc&fea ture=related
Cell Transport
Cell Transport • Diffusion = movement across a plasma membrane from HI to LO concentration • Osmosis = diffusion of water across a plasma membrane from HI to LO concentraion
Solution • Solution = homogeneous mixture of 2 or more substances • Made up of: – Solute = part that gets dissolved – Solvent = part that does the dissolving • Water is the UNIVERSAL SOLVENT
Types of Cell Transport • Water can move freely through the plasma memebrane, but can Solute? ? ? • NO! • Water will move to reach equilibrium since the solute cannot • Which way will the water move? • Depends on the TYPE OF SOLUTION the cell is in
Types of Solution • Hypertonic – Solute concentration is higher in solution than cell – Water moves OUT – Cell shrinks • Hypotonic – Solute concentration is lower in solution than cell – Water moves IN – Cell Swells • Isotonic – Solute concentration is equal in solution and in cell – Water moves IN and OUT – Cell stays the same
Hypertonic Solution Hypotonic Solution
Cell Transport • Active transport = movement of substances across membrane; requires ATP • Passive transport = movement of substances across membrane; does NOT require ATP
Active Transport • Goes against concentration gradient • Exocytosis = move particles OUT of cell • Endocytosis = move particels IN cell – 2 kinds of endocytosis: – Pinocytosis = movement of liquid IN cell – Phagocytosis = movement of solids IN cell – http: //www. youtube. com/watch? v=4 g. Ltk 8 Yc 1 Zc&NR=1
Exocytosis
Endocytosis
Passive Transport • Goes with concentration gradient • Osmosis = movement of water across a membrane with concentration gradient • Facilitated Transport = movement of substances across a membrane with concentration gradient with the help of a carrier protein • http: //www. youtube. com/watch? v=s 0 p 1 ztrb. X PY&feature=related
Facilitated Transport
Turgor Pressure and Plasmolysis • http: //www. youtube. com/watch? v=GOxou. JUt Eh. E&feature=related
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