The Plasma Membrane - Gateway to the Cell 7/30/2019 The Plasma Membrane - Gateway to the Cell G. Podgorski, Biol. 1010

Homeostasis Balanced internal condition of cells The Plasma Membrane 7/30/2019 Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma membrane controlling what enters & leaves the cell G. Podgorski, Biol. 1010

Functions of Plasma Membrane The Plasma Membrane 7/30/2019 Functions of Plasma Membrane Protective barrier Regulate transport in & out of cell (selectively permeable) Allow cell recognition Provide anchoring sites for filaments of cytoskeleton G. Podgorski, Biol. 1010

Functions of Plasma Membrane The Plasma Membrane 7/30/2019 Functions of Plasma Membrane Provide a binding site for enzymes Interlocking surfaces bind cells together (junctions) Contains the cytoplasm (fluid in cell) G. Podgorski, Biol. 1010

Structure of the Cell Membrane The Plasma Membrane 7/30/2019 Structure of the Cell Membrane G. Podgorski, Biol. 1010

Cell or Plasma Membrane Composed of double layer of phospholipids and proteins Surrounds outside of ALL cells Controls what enters or leaves the cell Living layer Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Cholesterol Outside of cell Phospholipids 6 6

The Plasma Membrane 7/30/2019 FLUID MOSAIC MODEL FLUID- because individual phospholipids and proteins can move side-to-side within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. G. Podgorski, Biol. 1010

Mosaic

Cell Membrane Polar heads are hydrophilic “water loving” The Plasma Membrane Cell Membrane 7/30/2019 Polar heads are hydrophilic “water loving” Nonpolar tails are hydrophobic “water fearing” Makes membrane “Selective” in what crosses G. Podgorski, Biol. 1010

Cell Membrane Hydrophobic molecules pass easily; hydrophilic DO NOT The Plasma Membrane Cell Membrane 7/30/2019 The cell membrane is made of 2 layers of phospholipids called the lipid bilayer Hydrophobic molecules pass easily; hydrophilic DO NOT G. Podgorski, Biol. 1010

Semipermeable Membrane The Plasma Membrane Semipermeable Membrane 7/30/2019 Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O G. Podgorski, Biol. 1010

video

Types of Transport Across Cell Membranes The Plasma Membrane 7/30/2019 Types of Transport Across Cell Membranes G. Podgorski, Biol. 1010

Simple Diffusion Requires NO energy The Plasma Membrane 7/30/2019 Simple Diffusion Requires NO energy Molecules move from area of HIGH to LOW concentration G. Podgorski, Biol. 1010

The Plasma Membrane 7/30/2019 DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY G. Podgorski, Biol. 1010

Diffusion of Liquids The Plasma Membrane 7/30/2019 G. Podgorski, Biol. 1010

Diffusion through a Membrane The Plasma Membrane 7/30/2019 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) G. Podgorski, Biol. 1010

Diffusion across a membrane Semipermeable membrane The Plasma Membrane 7/30/2019 Osmosis Diffusion across a membrane Diffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute) Semipermeable membrane G. Podgorski, Biol. 1010

Diffusion of H2O Across A Membrane The Plasma Membrane 7/30/2019 Diffusion of H2O Across A Membrane High H2O potential Low solute concentration Low H2O potential High solute concentration G. Podgorski, Biol. 1010

http://highered. mcgraw-hill http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html video

Cell in Isotonic Solution The Plasma Membrane 7/30/2019 Cell in Isotonic Solution 10% NaCl 90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCl 90% H2O What is the direction of water movement? equilibrium The cell is at _______________. G. Podgorski, Biol. 1010

Cell in Hypotonic Solution The Plasma Membrane 7/30/2019 Cell in Hypotonic Solution 10% NaCl 90% H2O CELL 20% NaCl 80% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

Cell in Hypertonic Solution The Plasma Membrane 7/30/2019 Cell in Hypertonic Solution 15% NaCl 85% H2O ENVIRONMENT CELL 5% NaCl 95% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

Cells in Solutions The Plasma Membrane 7/30/2019 G. Podgorski, Biol. 1010

NO NET MOVEMENT OF H2O (equal amounts entering & leaving) The Plasma Membrane 7/30/2019 Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS G. Podgorski, Biol. 1010

Osmosis in Red Blood Cells The Plasma Membrane 7/30/2019 Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic G. Podgorski, Biol. 1010

isotonic hypotonic hypertonic hypertonic isotonic hypotonic The Plasma Membrane 7/30/2019 isotonic hypotonic hypertonic hypertonic isotonic hypotonic G. Podgorski, Biol. 1010

Three Forms of Transport Across the Membrane The Plasma Membrane Three Forms of Transport Across the Membrane 7/30/2019 G. Podgorski, Biol. 1010

Passive Transport Simple Diffusion Doesn’t require energy The Plasma Membrane 7/30/2019 Passive Transport Simple Diffusion Doesn’t require energy Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out. G. Podgorski, Biol. 1010

Facilitated diffusion The Plasma Membrane 7/30/2019 Passive Transport Facilitated diffusion Doesn’t require energy Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. G. Podgorski, Biol. 1010

Active Transport Requires energy or ATP The Plasma Membrane 7/30/2019 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient G. Podgorski, Biol. 1010

The Plasma Membrane 7/30/2019 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump G. Podgorski, Biol. 1010

http://highered. mcgraw-hill http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html