7-3 Cell Boundaries

7-3 Cell Boundaries

Cell MembraneThe cell membrane regulates what enters and leaves the cell and also provides protection and support. The composition of nearly all cell membranes is a double- layered sheet calles a lipid bilayer.

The cell membrane regulates what enters and leaves the cell and also provides protection and suport. Lipid Bilayer- A membrane with a doble- layer

Cell WallsThe main function of the cell wall is to provide support and protection of the cell.

Cytoplasm Contains a solution of many different substances in water.Solution- A mixture of two or more substances.Solute Substances dissolved in the solution.

Concentration A solution is the mass of solute in a given volume of solution.Mass/ Volume12 Grams of salt3 Lt. Water12 Grams of Salt6 Lt. of WaterWhat solution has the most concentration?ConcentrationThe first solution is twice as concentrated as the second solution.12 g./ 3 L. or 4 g/L

12 g./6L or 2g/LMore concentrationIf you dissolved 12 grams of salt in 3 liters of water, what is the concentration for salt in the solution?Suppose you added 12 more grams of salt to the solution. What would be the resulting concentration?What if you then added another 3 liters of water to that solution concentration?Which solution of the ones discussed would be called the most concentrated?DiffusionParticles move constantly. The particles tend to move from an area where they are more concentrated to an area where they are less concentrated.

Equilibrium- when the concentration of the solute is the same throughout a system.Diffusion depends upon random particle movemnts, substances diffuse across membranes without requiring the cell to use energy.OsmosisIs the diffusion of water through a selectively permeable membrane.

PermeableSome substances can pass across then and others cannot. Isotonic- The concentration of solutes is the same inside and outside. Same Strength

Hypertonic Solution has a higher solute concentration than the cell. Above Strength

Hypotonic Solution has a lower solute concentration than the cell. Below Strength

Watch this for a better explanation on hypertonic and hypotonic http://www.youtube.com/watch?v=DpVbcJY4amA

http://www.youtube.com/watch?v=1vQzqk2hzj8&feature=related

Gather your thoughtsIn the beaker on the left, which solution is hypertonic and which is hypotonic? Pg. 185

In this model, to which material is the membrane permeable, water or sugar?

Visual Activitywww.phschool.comCode: cbp-3075Osmotic pressureFor organisms to survive, they must have a way to balance the intake ans loss of water.

Cells in large organisms are not in danger of bursting.

Plant cells and bacteria are surrounded by tough cel walls. The cell walls prevent the cells from expanding even under tremendous osmotic pressure. Facilitated DiffusionCell membranes have protein channels that make it easy for certain molecules to cross the membrane.

Cell membrane protein facilitate the diffusion of glucose, or other substances across the membrane.

The net movement of molecules across a cell membrane will occur only if there is a higher concentration of the particular molecules on one side than on the other side. No energy is required.

Active TransportSometimes it must move materials in the opposite direction, against concentracion difference.

It requires energy.

It can be by transport proteins or pumps that are found in the membrane.

Larger molecules can be processes by endocytosis and exocytosis.

EndocytosisThe process of taking material into the cell by means of infolding of the cell membrane.

The poket that results breaks loose from the outer portion of the cell membrane and forms a vauole

PhagocytosisThe cell engulfs particle and package it within a food vacuole.

PinocytosisCells take up liquid form the surrounding enviroment by introducing valuoles of water.

The release of large amounts of material from the cell. The membrane of the vacuole surrounding the material fuses with the cell membrane forcing the contents out of the cell.

Quick LabHow can you model permeability in cells?

Materials: graduated cylinder, plastic sandwich bag, starch, twist tie, 500 ml beaker, iodine solution

Procedure:1- Pour about 50 ml of water into a plastic sandwich bag. Add 10 ml of starch. Secure the bag with a twist tie, and shake it gently to mix in the starch.

2- Put on your goggles, plastic gloves and apron.3- Pour 250 ml of water into a 500 mL beaker.4- Place the sandwich bag of water and starch into the beaker of water and iodine.5- After 20 minutes, look at the sandwich bag in the beaker. Observe and record any changes that occurred.

http://staff.tuhsd.k12.az.us/gfoster/standard/bcell1.htmhttp://io.uwinnipeg.ca/~simmons/cm1503/membranefunction.htm