Movement through Cells Inside Cell Cell membrane Movement through Cells All organisms are made of cells Cells are mostly liquid. Surrounding the cells is also liquid.

Role of the Cell Membrane 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

Role of the Cell Membrane Large particles can only enter and exit the cell through the protein channels BUT Small particles can enter and exit straight through the lipid bilayer!!

Particles of liquids + = solution All particles of matter--atoms or molecules are constantly in motion. In liquids, the molecules randomly move.* A solution is made when particles of sugar, salt, or oxygen, etc. are dissolved in liquids + = solution

What is a solution? Liquid mixture of 2 or more substances. Water - solvent The substance dissolved in the water - solute Concentration = mass of solute/volume of solvent Concentration is similar to density.

Which beaker contains a more concentrated sugar Problem: Imagine you have a beaker filled with sugar water. Imagine you add double the amount of sugar to the water. Sugar Which beaker contains a more concentrated sugar solution?

Concentration of Solutions Molarity (M) = unit of concentration used in biochemistry The greater the molarity of a solution the greater the concentration. 0.25M sucrose solution (read as 0.25 molar) has half of the concentration of a 0.50M sucrose solution.

Particles in solution cross the cell membrane 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

Diffusion 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.

Diffusion Demonstration Food coloring (solute)+ water (solvent). What do you think will happen over time in the solution? Discuss at table and draw on white board.

Diffusion 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.* See molecular workbench and answer questions. (p1-6)

Diffusion Across a Cell Membrane 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!

Diffusion Across a Cell Membrane Design an experiment to test the effect of the size of a particle on its ability to diffuse. Your materials:

Conclusions for Diffusion: Small particles diffuse __________ than large particles across a cell membrane Only substances that can permeate the cell membrane can diffuse across it. Diffusion occurs from areas of ________concentration of solute particles to areas of ________ concentration. The movement of particles is always taking place. faster high low The cell expends NO ENERGY on the process of diffusion

Particles dissolved in water cross the cell membrane Diffusion Osmosis

Osmosis: A special type of diffusion Diffusion of water through a selectively permeable membrane. Water diffuses from where there is less solute (sugar, salt, etc.) to where there is more solute. Osmotic pressure is the force that is placed on a selectively permeable membrane due to the flow of water into one side more than the other.  See molecular workbench and answer questions OSMOTIC PRESSURE-placed on semipermeable membrane

Osmosis: 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.

Osmosis Inside cell Outside cell 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

Osmosis in Animals 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 (more concentrated) solution? (saltwater)* 2. What happens if blood cells are placed in a hypotonic (less concentrated) solution? (distilled water)*

Osmosis in Animals

Osmosis in Animals 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 ______________________ to each other. isotonic

Osmosis in Plants Healthy Plant 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)? Healthy Plant

Osmotic Pressure = Pressure created by water moving into a hypertonic cell. 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.

Osmotic Pressure = Pressure created by water moving into a hypertonic cell. 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

Osmosis in one-celled organisms In one-celled organisms the cell does not burst when in a hypotonic solution (for example pond water). One-celled organisms have mini-pumps called contractile vacuoles. As water enters the cell, it is pumped out by this organelle.

Osmosis and Contractile Vacuoles *

Osmosis: The cell expends NO ENERGY on osmosis Because osmosis is a special type of diffusion The cell expends NO ENERGY on osmosis Now: Complete Worksheet on OSMOSIS

Particles cross the cell membrane Diffusion Osmosis Facilitated diffusion Active transport

Facilitated Diffusion 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.  

Facilitated Diffusion 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.

Particles cross the cell membrane Diffusion Osmosis Facilitated diffusion Active transport

Active Transport Active Transport: Movement of material across the cell membrane in the OPPOSITE direction of diffusion. During diffusion particles always moves in the direction of high concentration to low concentration (=concentration gradient). During active transport particles move against the concentration gradient from low concentration to high concentration.

Complete Packet on Transport through a Cell Membrane Active Transport 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*.   See molecular workbench. Complete Packet on Transport through a Cell Membrane The cell EXPENDS ENERGY (found in molecules of ATP) on Active Transport

Connections to Daily Life 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.