1.4 Membrane Transport Skills: Understanding: Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis Vesicles move materials within cells Skills: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions Applications: Structure and function of sodium potassium pumps for active transport and potassium channels for facilitated diffusion in axons Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis Nature of science: Experimental design: accurate quantitative measurements in osmosis experiments are essential

Movement across membranes Endocytosis (1) Exocytosis (2) Simple diffusion (3) Facilitated diffusion (4) Active transport (5) Osmosis (6)

Movement across membranes Name of movement How it works Diagram/picture Example of this movement Create a presentation for your mode of movement (5 mins maximum) To be presented on: Monday 29th October

Facilitated diffusion Name of movement How it works Example Drawing Endocytosis Exocytosis Simple diffusion Facilitated diffusion Active Transport Osmosis

Osmosis Movement of water from a low solute concentration to a high solute concentration through a partially permeable membrane Skills: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions

Hypotonic Solution Place a plant cell into pure water Water goes down water potential gradient and into the cell by osmosis Will not continue to absorb water until it bursts Strong cellulose walls Cell will gain mass Skills: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions

Hypertonic Solution Place a plant cell into salt water Water lost from the cell Water goes down water potential gradient out of the cell by osmosis Cell loses turgidity If it continues = cytoplasm and vacuole shrink Cell will lose mass Skills: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions

Label your diagrams What is happening? Which direction is water moving Why? What type of solution are each of these cells in?

Prescribed Practical Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions Skills: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions

Prescribed Practical From your raw data Find the percentage change in mass Plot a scatter graph of solute concentration vs. % change in mass (there will be a negative Y axis as well) Draw a line of best fit What is the osmolarity of the potato (where does your line of best fit meet the X axis?) Skills: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions