Osmosis Aim: How does osmosis occur through a semi-permeable membrane Osmosis Aim: How does osmosis occur through a semi-permeable membrane? Objectives: Students should be able to. 1-Define osmosis, semi-permeable membrane & passive transport 2-Explain the concept of osmosis & passive transport. 3-Define & explain hypotonic, hypertonic and isotonic solution.

4-Students work in pairs or groups to brainstorm by using critical thinking skills to solve problems and analyze diagrams. Do now or development of the lesson can use animation of osmosis with questions from the internet. Do Now: can use enter slip written on the board. Write two things you learned from yesterday lesson & one question too.

Vocabulary development: 1-Osmosis = is the ability of water molecule(s) = H2O to travel from an area of high concentration (quantity) of water to an area of low concentration of water without applying energy through a semi-permeable membrane. 2-Passive transport = is the ability of a substance to travel from an area of high concentration (quantity) of that substance to an area of low concentration of that substance without applying energy. 3-Gradient = is the difference in measurement of two different ends or side of a parameter.

4-Semi-permeable membrane = is selective about the substance that can pass through a porous barrier. 5-Equilibrium = is when the situation is stabled or evenly balanced. It can be when there is no concentration gradient.

6-Hypertonic solutions are those in which there is a lot of solute (ex: salt & protein) and hence lower water content is present. 7-Hypotonic solutions are those with less solute and a high water content. 8-Isotonic solutions have equal (iso-) concentrations of substances. Water potentials are thus equal, although there will still be equal amounts of water movement in and out of the cell, the net flow is zero.

Do now: Analyze the diagram and identify the section with “high concentration” of H2O, “low concentration” of H2O, state of equilibrium, and semi-permeable membrane.

A special case of passive transport occurs with osmosis A special case of passive transport occurs with osmosis. Osmosis is the diffusion of water across a selectively permeable membrane (semi-permeable). All cells have some amount of dissolved salts, proteins and such, the flow of water across the plasma membrane depends upon the concentration of water in the liquid that the cells are in.

In humans the concentrations are equal inside and outside the cell In humans the concentrations are equal inside and outside the cell. Therefore, water will neither enter nor exit the cell. However, if the cells are removed from the body and placed in a solution with lower water content, the water will leave the cells thru osmosis.

If the solution has a higher water concentration, the water will enter the cell causing swelling of the cell. Osmosis across plasma membranes is crucial to the functioning of many biological systems, including water uptake by plant roots, adsorption of dieting water from intestine and the reabsorption of water and minerals in the kidneys.

Circle = protein, dissolved salt Circle = protein, dissolved salt. Write and explain when does osmosis occur?

Solute = protein or dissolved salt.

The left has a high concentration of water and the right a low concentration. By diffusion, water will naturally level out and pass through the membrane. The solute however will not be able to diffuse, as they can't fit through the membrane. Therefore we define osmosis as: the net movement of water (= solvent) from a dilute area of solute to a concentrated area of solute of a solution, through a partially permeable membrane.

Write and explain why the solutes are not able to travel through the membrane? Also, write and explain when does osmosis reach a state of equilibrium?

Isotonic - same salt concentration on either side of membrane Hypertonic - salt concentration in solution is higher outside of cell and water leaves cell. Hypotonic - salt concentration in solution is lower outside of cell and water enters cell.

Read the paragraph below and solve the problem: Hypertonic solutions are those in which more solute (and hence lower water potential) is present. Hypotonic solutions are those with less solute (and hence higher water potential). Isotonic solutions have equal (iso-) concentrations of substances. Water potentials are thus equal, although there will still be equal amounts of water movement in and out of the cell, the net flow is zero.

Label the parts of the diagram that are isotonic, hypertonic, and hypotonic and write and explain why it occurs?