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. 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!!

4. Particles of liquids • All particles of matter--atoms or molecules are constantly in motion. • In liquids, the molecules randomly move.* • In organisms, molecules of sugar, salt, oxygen etc. are dissolved in liquids = solutions

5. 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.

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

7. Concentration of Solutions • Calculate the concentration in grams/1 liter for: • A) Example: 100 grams of sucrose in 200 liters of water. • Set up: B) 300 grams of sucrose in 100 liters of water. C) 200 grams of sucrose in 1000 liters of water D) Which of the solutions, A, B, or C, is the most concentrated? 3 g/liter .2 g/liter 100grams/200 liters = 1g/2 liters = 1 ÷ 2 = .5g/liter

8. 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

9. 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.

10. Diffusion Demonstration • Food coloring + water

11. 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.*

12. 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!

13. 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:

14. 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 high concentration of solute particles to areas of low concentration. • The movement of particles is always taking place. faster The cell expends NO ENERGY on the process of diffusion

15. Particles cross the cell membrane • Diffusion • Osmosis

16. 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).

17. 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.

18. Osmosis • When solutions on both sides of the cell membrane do not have equal concentration they are described as hypotonic or hypertonic. • Hyptonic = lower concentration of solute • Hypertonic = higher concentration of solute Overall Direction of Water flow

19. 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)*

20. Osmosis in Animals

21. 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

22. 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)?

23. Osmosis in Plants

24. 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.

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.