Diffusion and Osmosis Pre-AP Biology

Bellwork You have a raisin and you stick it in a… Glass of Water – What will happen to the raisin? Glass of Salty Water from the Ocean- What will happen to the raisin?

Objectives Distinguish between diffusion and osmosis Identify environmental factors that influence the rate of diffusion Define tonicity Distinguish between isotonic, hypotonic and hypertonic solutions

Key Terminology Diffusion Osmosis Isotonic Hypotonic Hypertonic

Solution Solution is made of the solute and the solvent Solute is the substance dissolved in the solvent Examples of solute-glucose, NaCl, sucrose Solvent is the dissolving agent- what the solute is dissolved in Example of solvent - water

Diffusion-Movement of Solutes Solute molecules move from a high concentration to a low concentration. Solutes move away from the most concentrated region Movement of dye in a beaker of water

Diffusion How quickly the molecules move dependent on temperature Higher the temperature the faster the molecules will move

Diffusion at Equilibrium Diffusion continues until they reach equilibrium-same concentration of molecules throughout the solution Molecules at equilibrium continue to move but no net movement- Don’t move in only one direction, instead move in all directions equally.

Practice Utube Problem 10% glucose, 1% starch 0% glucose, 0% starch Membrane permeable to glucose but not to starch

Osmosis Definition: Diffusion of water Water will move in the direction where there is a high concentration of solute.

Osmosis-Diffusion of Water Water moves in response to differences in concentration of solutes (number of solutes per volume) between solutions. The size of the solute does not matter only the number of solutes per volume Will water move towards Solution A or Solution B? Explain

Example: Salt Sucks Salt is a solute, when it is concentrated inside or outside the cell it will pull water in its direction.

Tonicity:Compare two solutions separated by a membrane Compare solute concentration inside and outside a cell Isotonic – Concentration of salt equal between the two solutions – no net movement of water

Tonicity (cont) Hypotonic- Comparing the solution outside and inside of cell, the hypotonic solution is the solution with the lower solute concentration

Tonicity (cont.) Hypertonic- Comparing the solution inside and outside the cell, the hypertonic solution has the higher concentration of solutes

Think-Pair-Share Extensive irrigation on Phoenix golf courses causes salts to accumulate in the soil. Why might this be harmful to the turf grass on these courses? 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class 3

Red Blood Cells Isotonic solution outside- no net movement of water Red blood cell – regular shape Hypotonic solution outside- water moves into cell Red blood cell – burst Hypertonic solution outside- water moves out of cell Red blood cell – shrivel

Red Blood Cells in solutions of varying osmolarity. 100 mos 200 mos 300 mos 400 mos 500 mos hypotonic isotonic hypertonic

Think-Pair-Share You have been sick for a couple days unable to keep any food or drink in your stomach resulting in severe dehydration. You are taken to the hospital and given intravenous solutions. The intravenous solutions are a saline solution not pure water. Why? 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class 3

Summarize two key points in your note taker in your own words! Paraphrase Summarize two key points in your note taker in your own words! 6. Paraphrase student writes down one or two main ideas directly from the text or notes student now paraphrases these ideas in their own words teacher provides feedback 6