All organisms are made of cells Cells are mostly liquid. Surrounding the cells is also liquid. * The cell membrane separates the cell from the liquid it is bathed in. a) It allows only certain particles to enters and leave the cell. Therefore the cell membrane is considered Selectively Permeable ____________________ b) The cell membrane is made up of two parts: protein channels ___________________________ lipid bilayer ____________________________ All particles of matter--atoms or molecules are constantly in motion. In liquids, the molecules randomly move.* In organisms, molecules are dissolved in liquids = solutions Liquid mixture of 2 or more substances. The substance with the greater volume = solvent The substance with the smaller volume = solute Concentration = mass of solute/ volume of solution Concentration is similar to density. Calculate the concentration in grams/liter for: B) 100 grams of glucose in 2000 liters of water. .05 grams/liter C) 300 grams of fructose A) 100 grams of sucrose in 200 liters of water. Set up: 100grams/200 liters = .5g/liter in 1200 liters of water .25 grams/liter D) 300 grams of dextrose in 100 liters of water 3 grams/liter Particles within an organism must continuously enter and exit the cell through the cell membrane using one of four processes: • Diffusion • Osmosis • Facilitated diffusion • Active transport The movement of a substance (liquid or gas) from areas of high concentration to areas of low concentration. The motion is random --eventually all particles spread out evenly throughout the solution = equilibrium. Food coloring + water Once equilibrium is reached, the movement of particles continues, but it is equal in all directions. Solution remains in equilibrium. Particles remain equally spaced out.* The cell membrane allows many types of particles (ions, atoms, molecules) to move in and out of the cell by diffusion. But some types of molecules are not able to cross the membrane. What determines whether a particle can cross the cell membrane? Complete Worksheet to find out! Design an experiment to test the effect of the size of a particle on its ability to diffuse. Your materials: Small particles diffuse __________ faster than large particles across a cell membrane •Only substances that can permeate the cell membrane can diffuse across it. •Diffusion occurs from areas of high concentration of solute particles to areas of low concentration. •The movement of particles is always taking place. The cell expends NO ENERGY on the process of diffusion •Diffusion •Osmosis •Facilitated diffusion •Active transport Diffusion of water through a selectively permeable membrane. Water diffuses from where there is less concentration of a solute (pure water) to an area of more concentration of a solute (water + other substance). Osmosis results in equilibrium when the concentration of the solutions is equal on both sides of the membrane. A solution in equilibrium is also referred to as isotonic. When solutions on both sides of the cell membrane do not have equal concentration they are described as hypotonic or hypertonic. Hypotonic = lower concentration of solute Hypertonic = higher concentration of solute Overall Direction of Water flow At your table: Draw a picture illustrating #1 and #2 below and answer the questions! Use arrows to show the movement of water. 1. What happens if blood cells are placed in a hypertonic solution? (saltwater)* 2. What happens if blood cells are placed in a hypotonic solution? (distilled water)* Under normal bodily conditions, blood is the liquid that surround the cells. Blood has the same concentration of solutes as those inside the cell. This means that blood and cytoplasm are isotonic ______________________ to each other. At your table: Draw a picture illustrating #1 ,#2 and #3 below and answer the questions! Use arrows to show the movement of water. 1) What happens if plant cells are placed in a hypertonic solution (example: salt water)? 2) What happens if plant cells are placed in a hypotonic solution (example: distilled water)? 3) What happens if plant cells are placed in an isotonic solution (example: water with minerals)? A plant cell is filled with proteins, sugars, salts. The cytoplasm of plant cells is more concentrated than fresh water The plant cell is hypertonic relative to freshwater Since freshwater is used to water plants (not blood), the plant cells fill up with water. Diffusion Osmosis* With your table answer the following question: Why doesn’t a plant cell burst (like a blood cell) when placed in freshwater? (Hint: What is a MAJOR difference between plant and animal cells?) Cell Wall is RIGID In one-celled organisms the cell does not burst when in a hypotonic solution. One-celled organisms have mini-pumps called contractile vacuoles. As water enters, it is pumped out of the cell. * Because osmosis is a special type of diffusion The cell expends NO ENERGY on osmosis Now: Complete Worksheet on OSMOSIS •Diffusion •Osmosis •Facilitated diffusion •Active transport Movement of specific molecules through protein channels in the cell membrane The protein channels are specific to a type of particle. Example: glucose moves through a protein channel that is specific to glucose. The movement of particles is two ways but always from areas of high concentration (hypertonic) to areas of low concentration (hypotonic). Cells use facilitated diffusion for substances such as salt, sugars and starches*. The cell expends no energy on facilitated diffusion. •Diffusion •Osmosis •Facilitated diffusion •Active transport Active Transport: Movement of material across the cell membrane in the OPPOSITE direction of diffusion. Because the flow of solute is from an area of LESS concentration to an area of MORE concentration the solute must be pumped by the cell*. The cell EXPENDS ENERGY (found in molecules of ATP) on Active Transport You will be assigned an article on a topic with a group of students. Read and discuss the article with your group and present the information to the class…as a poster, as a play, as a song, etc. Topics Facilitated diffusion, insulin and diabetes Diffusion of oxygen into our lungs and emphysema Diffusion and alcohol Pregnancy and diffusion of nutrients between mother and fetus.