All organisms are made of cells Cells are mostly liquid. Surrounding the cells is also liquid. Inside Cell 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 lipid bilayer protein channels b) The cell membrane is made up of two parts: ___________________________ ____________________________

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!!

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

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 (solute)+ water (solvent). What do you think will happen over time in the solution?

The food coloring demonstration showed particles diffusing around a container without a cell membrane. However, particles can also diffuse ACROSS a cell membrane until there is an equal concentration on both sides=equilibrium.

A concentration gradient is a measurement of how the concentration of something changes from one place to another. If we picture each individual molecule as a little blue dot, a constant concentration of molecules (no gradient) would look like the picture below:

A concentration gradient, with a higher concentration of molecules on the right than on the left would look like the picture below

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

But some types of molecules cannot 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 __________ 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 The cell expends NO ENERGY on the process of diffusion high low

Diffusion Osmosis

Diffusion of water through a selectively permeable membrane. Water diffuses from where there is low concentration of solute (sugar, salt, etc.) to where there is a greater concentration of solute

Pressure builds up inside of the cell when water flows in. (just like a water balloon!)

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 Inside cell Outside cell

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)*(saltwater)* 2. What happens if blood cells are placed in a hypotonic (less concentrated) 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 ______________________ to each other. isotonic

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

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.

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.

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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*.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. 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.

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*. cell*. See molecular workbench.molecular workbench Complete Packet on Transport through a Cell Membrane 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.