Cell Membrane and Cell Wall: Structure and Function

Transcription

1 Cell Membrane and Cell Wall: Structure and Function

2 What are you going to learn? 1. The molecular arrangement of the cell membrane. 2. Components of the cell wall. 3. Understand how molecules pass through the cell membrane. 4. Be able to determine what molecules can and cannot pass through the membrane.

3 Cell Membrane 1. Cell membranes are present in ALL cells. They control the movement of substances into and out of the cell. 2. A biological membrane, also called the plasma membrane, that surrounds a cell and selectively controls which substances can enter or leave the cell.

4 Components of the Cell Membrane The cell membrane is made up a many phospholipids. The phosphate head is hydrophilic. The fatty lipid tails are hydrophobic.

5 Activity You will be given a handful of phospholipids. Knowing that the body is approximately 70% water. Water is in cells and between cells. How do you think the membrane is arranged? Use the phospholipids and arrange how you think it might look.

6 Cell Membrane

7 Cell Membrane Regulates what enters and leaves the cell and also provides protection and support Composition is a lipid bilayer, which gives it a flexible structure and forms a strong barrier between the cell and it s surroundings. Phospholipids are arranged in this way because the tails are hydrophobic (don t like water)

8 Cell Membrane - Proteins In addition to lipids most cell membranes contain proteins that are embedded, they form channels or pumps that help materials across the membrane.

9 Cell Membrane - Carbohydrates Carbohydrates are attached to the proteins, many act like chemical identification cards, allowing individual cells to identify one another.

10 Cell Membrane There are so many molecules in the cell membrane scientist call it a mosaic of different molecules. (mosaic = a large structure made of many small structures) Fluid Mosaic Model

11 Cell Wall The main function of the cell wall is to provide support and protection for the cell. Made from firm fibers of complex carbohydrates called cellulose. Humans can t break cellulose down, that is why it is considered roughage.

12 How do things cross cell boundaries?

13 Solutions Solution: a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent) ex. Sea water, soda, lemonade Solute: What is being dissolved ex. Salt, Sugar, lemon juice Solvent: What is doing the dissolving ex. Water

14 Passive Transport Diffusion Movement of particles from an area of high concentration to an area of low concentration=diffusion (a type of passive transport)

15 Passive Transport Diffusion Solute particle move toward equilibrium.

16 Passive Transport Passive Because diffusion depends upon random particle movements, substances diffuse across membranes without needing ENERGY!!

17 Diffusion of Particles What can pass through the membrane by diffusion Small, uncharged molecules such as O2 and CO2. What cannot pass through by diffusion Large molecules Charged molecules Have to use protein channels Ex. water and sucrose (disaccharide)

18 Facilitated Diffusion Proteins embedded in the cell membrane help large (glucose C6H12O6) and or charged molecules/ions (H2O or Na+) through the membrane through a channel.

19 Review Question 1. Explain why the cell membrane is arranged the way it is? 2. What is the purpose of the proteins and carbohydrates embedded in the cell membrane? 3. Identify the solute and solvent from the following solutions. Sugar water Lemon water 4. Explain diffusion, by using the word concentration in your response. 5. How do terms passive transport, diffusion, and facilitated diffusion relate?

20 Vocabulary Phospholipid Hydrophobic Hydrophilic Phospholipid bilayer Selectively permeable membrane Equilibrium Concentration gradient Passive transport Facilitated diffusion Solute Solvent Solution Please define these using these notes or DE interactive glossary on a vocabulary wkst.