Cell Membrane & The Cellular Processes Osmosis & Diffusion

The Plasma Membrane - Gateway to the Cell The Plasma Membrane 6/11/2018 The Plasma Membrane - Gateway to the Cell G. Podgorski, Biol. 1010

Research Question Find some functions of the plasma membrane You have 2 minutes to Google your responses… Begin NOW!!

Functions of Plasma Membrane The Plasma Membrane 6/11/2018 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 6/11/2018 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 6/11/2018 Structure of the Cell Membrane G. Podgorski, Biol. 1010

What is Homeostasis???

Homeostasis Balanced internal condition of cells The Plasma Membrane 6/11/2018 Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma membrane controlling what enters & leaves the cell G. Podgorski, Biol. 1010

Research Question Draw and label what a Phospholipid looks like You have 2 minutes Begin NOW!!

Phospholipids Contains 2 fatty acid chains that are nonpolar The Plasma Membrane 6/11/2018 Phospholipids Contains 2 fatty acid chains that are nonpolar Make up the cell membrane Polar Head water loving Head is polar & contains a –PO4 group & glycerol Non-polar tail Water fearing G. Podgorski, Biol. 1010

Cell Membrane Polar heads are hydrophilic “water loving” The Plasma Membrane Cell Membrane 6/11/2018 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 6/11/2018 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

The Plasma Membrane 6/11/2018 Solubility Materials that are soluble in lipids can pass through the cell membrane easily. G. Podgorski, Biol. 1010

Semipermeable Membrane The Plasma Membrane Semipermeable Membrane 6/11/2018 Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O G. Podgorski, Biol. 1010

Types of Transport Across Cell Membranes The Plasma Membrane 6/11/2018 Types of Transport Across Cell Membranes G. Podgorski, Biol. 1010

Transport across the Membrane There are 2 main types of transport across the cell membrane Passive Transport – requires NO energy Active Transport – requires Energy (ATP) to move particles across the cell membrane

Passive Transport Passive Transport requires NO energy in order to move particles across the cell membrane Like going down a slide

Diffusion Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.

Diffusion of Liquids The Plasma Membrane 6/11/2018 G. Podgorski, Biol. 1010

Diffusion Solute molecules moving from an area of high concentration to an area of low concentration Random motion drives diffusion Equilibrium is reached when there is an even distribution of solute molecules (water) 2 3 1 4

Osmosis = Diffusion of H2O Across A Membrane The Plasma Membrane 6/11/2018 Osmosis = Diffusion of H2O Across A Membrane Draw this picture  High H2O potential Low solute concentration Low H2O potential High solute concentration G. Podgorski, Biol. 1010

Osmosis Diffusion of water through a semi-permeable membrane Semi-permeable: permeable to solvents (WATER), but not to large molecules High [water] to low [water] Dissolved molecules (i.e. glucose, starch) are called solutes REMEMBER: Water = solvent Glucose, Starch = solutes

Salt Sucks Salt draws water to where it is. Water wants to equal everything out. A simple rule to remember is: Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

3 Key Terms Hypo = below Hyper = above Iso = equal

Isotonic Solution The solution the cell is in is equal to the inside of the cell. "ISO" means the same

Hypotonic The word "HYPO" means less There are less solute (salt) molecules outside the cell then inside the cell since salt sucks, water will move into the cell Animal cell could burst Plant cell wall keeps it from bursting

Hypertonic The word "HYPER" means more There are more solute (salt) molecules outside the cell. Water goes in the direction of the salt Cell may die if too much water is lost.

Osmosis in Living Cells Cellulose in cell wall Plasmolysis = cell membrane detaching from the cell wall (shrinking)

Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic Iso: Normal blood cells Hypertonic solution: the cells shrink Cell may die if too much water is lost. Crenation Hypotonic solution: In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.

Effect of Water on Cells Hypertonic Environment High [solute], low [water] Cell shrinks Hypotonic Environment High [water], low [solute] Cell fills with water, too much water can cause the cell to lyse Isotonic Environment [water] = [solute] Normal cell: everything is equal Hypertonic Hypotonic Isotonic

Osmosis in Plant Cells Hypertonic Plasmolysis Hypertonic: In plant cells, the central vacuole loses water and the cells shrink, causing wilting. Hypotonic Hypotonic: In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting

Review Passive Transport = _____ Energy used Diffusion is defined as: What occurs in osmosis? Identify the 3 types of solutions.