Movement through Cells

1. Movement through Cells • All organisms are made of cells • Cells are mostly liquid. Surrounding the cells is also liquid. *

2. 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

3. Cell Membrane

4. Particles of liquids • 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

5. What is a solution? • 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.

6. Concentration of Solutions • Calculate the concentration in grams/liter for: • A) 100 grams of sucrose in 200 liters of water. • Set up: B) 100 grams of glucose in 2000 liters of water. • 300 grams of fructose in 1200 liters of water • 300 grams of dextrose in 100 liters of water .05 grams/liter .25 grams/liter 100grams/200 liters = 3 grams/liter .5g/liter

7. Particles 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

8. 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.

9. Diffusion Demonstration • Food coloring + water

10. 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.*

11. 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!

12. 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:

13. Conclusions for Diffusion: • Small particles diffuse __________ than large particles across a cell membrane faster • 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

14. Particles cross the cell membrane • Diffusion • Osmosis • Facilitated diffusion • Active transport

15. Osmosis: A special type of diffusion • 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).

16. 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.

17. Osmosis • 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

18. 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 solution? (saltwater)* 2. What happens if blood cells are placed in a hypotonic solution? (distilled water)*

19. Osmosis in Animals

20. 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

21. Osmosis in Plants 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)?

22. Osmosis in Plants

23. 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.

24. Diffusion: Molecular Workbench • Diffusion • Osmosis*

25. 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

26. Osmosis in one-celled organisms • 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.

27. Osmosis and Contractile Vacuoles *

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

29. Particles cross the cell membrane • Diffusion • Osmosis • Facilitated diffusion • Active transport

30. 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.

31. 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.

32. Particles cross the cell membrane • Diffusion • Osmosis • Facilitated diffusion • Active transport

33. Active Transport • Active Transport: Movement of material across the cell membrane in the OPPOSITE direction of diffusion.

34. 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*. The cell EXPENDS ENERGY (found in molecules of ATP) on Active Transport

35. 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.