Transport Across the Plasma Membrane

Overview Certain substances must move into the cell to support metabolic reactions Certain substances must move into the cell to support metabolic reactions Some materials must be moved out of the cell because they have been produced as cellular waste Some materials must be moved out of the cell because they have been produced as cellular waste The Plasma Membrane is responsible for regulating these materials The Plasma Membrane is responsible for regulating these materials

Fluids Intracellular Fluid (ICF) – fluid contained within cells (cytosol) Intracellular Fluid (ICF) – fluid contained within cells (cytosol) Extracellular Fluid (ECF) – fluid outside the body cells Extracellular Fluid (ECF) – fluid outside the body cells –Interstitial Fluid – fluid between cells –Plasma – fluid in blood vessels –Lymph – fluid in lymphatic vessels

Solutions Solute – any substance dissolved in a fluid Solute – any substance dissolved in a fluid –Solutes in the body include gases, nutrients and ions Solvent – the fluid in which something is dissolved Solvent – the fluid in which something is dissolved –Water serves as the solvent in the body

Concentrations Concentration – the amount of solute in a solution Concentration – the amount of solute in a solution Concentration Gradient – the difference in concentration between 2 areas Concentration Gradient – the difference in concentration between 2 areas –Molecules can move “up” or “down” a concentration gradient

Passive Processes A substance moves down a concentration gradient through the membrane using only its own energy of motion (no ATP) A substance moves down a concentration gradient through the membrane using only its own energy of motion (no ATP) –Include Diffusion and Osmosis

Diffusion The movement of a substance from one place to another due to the substance’s kinetic energy. The net movement of particles is from an area of high concentration to an area of lower concentration until equilibrium is reached

Simple Diffusion Substances diffuse through the membrane by passing right through the lipid bilayer Substances diffuse through the membrane by passing right through the lipid bilayer –EX – oxygen, carbon dioxide, nitrogen, fatty acids, steroids, vitamins, water OR substances can pass though a channel in an integral protein OR substances can pass though a channel in an integral protein –EX - ions

Ion Channels Most membrane channels are ion channels Most membrane channels are ion channels Allow specific type of ion to pass by simple diffusion through a channel’s pore Allow specific type of ion to pass by simple diffusion through a channel’s pore Gated Channels – moves in one direction to let substances in and the other to let substances out Gated Channels – moves in one direction to let substances in and the other to let substances out

Facilitated Diffusion An integral protein assists a SPECIFIC substance across the membrane. An integral protein assists a SPECIFIC substance across the membrane. The substance binds to a transporter on one side of the membrane and is released on the other side after the transporter undergoes a change in shape The substance binds to a transporter on one side of the membrane and is released on the other side after the transporter undergoes a change in shape DOES NOT REQURE CELLULAR ENERGY (no ATP = Passive) DOES NOT REQURE CELLULAR ENERGY (no ATP = Passive) **This is how glucose enters the cell

Osmosis The net movement of water through a selectively permeable membrane The net movement of water through a selectively permeable membrane Water moves from high WATER concentration to low WATER concentration or.. Water moves from high WATER concentration to low WATER concentration or.. From low SOLUTE concentration to high SOLUTE concentration From low SOLUTE concentration to high SOLUTE concentration

Osmotic Pressure The pressure a solution containing solute particles that cannot pass through a membrane exerts on that membrane. The pressure a solution containing solute particles that cannot pass through a membrane exerts on that membrane. Depends on the concentration of the solute particles – the higher the concentration, the higher the osmotic pressure Depends on the concentration of the solute particles – the higher the concentration, the higher the osmotic pressure

Isotonic Solution Contains the same concentration of solutes as the cell Contains the same concentration of solutes as the cell –Cell maintains it’s shape and volume

Hypotonic Solution Has a lower concentration of solutes than the cell Has a lower concentration of solutes than the cell –Net movement of water into the cell will cause it to swell and eventually burst This is called hemolysis in red blood cells This is called hemolysis in red blood cells

Hypertonic Solution Concentration of solutes is greater than the cell Concentration of solutes is greater than the cell –Net movement of water out of the cell will cause the cell to lose volume, and shrink This is called crenation This is called crenation

Concentration of Blood The concentration of the salt in the blood is 0.9% NaCl The concentration of the salt in the blood is 0.9% NaCl Isotonic Solution (Normal Saline) = 0.9% NaCl Isotonic Solution (Normal Saline) = 0.9% NaCl Hypotonic Solution < 0.9% NaCl Hypotonic Solution < 0.9% NaCl Hypertonic Solution > 0.9% NaCl Hypertonic Solution > 0.9% NaCl

Check Point – Answer these questions in your notes What are the 2 types of fluids in the body? What are the 2 types of fluids in the body? What is a solute? What is a solute? In which direction is the net flow of molecules in diffusion? In which direction is the net flow of molecules in diffusion? What is the difference between simple and facilitated diffusion? What is the difference between simple and facilitated diffusion? How do ions get into/out of the cell? How do ions get into/out of the cell? What osmotic pressure? What osmotic pressure? What will happen to a red blood cell if it is placed in a solution with a concentration of 0.3%NaCl? What will happen to a red blood cell if it is placed in a solution with a concentration of 0.3%NaCl?