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Transcript
Continued 7-3 notes Cell Membrane • Regulates what enters and leaves • Flexible structure • Strong barrier Lipid Bi- layer • Water, oxygen, and carbon dioxide flow freely through the lipid bi-layer • Besides lipids the cell membrane also contains – Protein molecules: form channels and pumps to help move material across the cell membrane – Carbohydrate molecules attached to proteins…. act like ID cards, so cells can identify each other Cell Wall • porous enough to allow water, oxygen, carbon dioxide, and certain other substances to pass through easily • provide support and protection for the cell. • composed mostly of cellulose, a tough carbohydrate fiber Concentration • The concentration of a solution is the mass of solute in a given volume of solution, or mass/volume. • In this lab you need to make a solution that is 90% water and 10% sugar, and another that is 80% water and 20% sugar. • How will you do that? Diffusion • In a solution, particles move constantly. • They collide with one another and tend to spread out randomly. • The particles move from where it is too crowded to an area where there is more room… this is called diffusion • EZ pass analogy: Diffusion – Tolls are up to $6 to cross the tunnels into NYC – They are going to raise it even higher, during rush hour… – If they don’t need the money then why would they do that? Equilibrium • The particles keep moving and eventually both areas are balanced….this is called equilibrium. • Particles will continue to move back and forth but because numbers are equal, no change in concentration Facilitated Diffusion • Substances, that are too large or have too strong of a charge can still get across the cell membrane• How? Proteins act as tunnels or channels • This is still diffusion though, and does not require the cell’s energy- Example • Red blood cells: have a protein channel for glucose. • Only glucose can pass through this channel, and it can move through in either direction. • 100’s of different protein channels have been found that allow particular substances to cross different membranes. Active Transport • Sometimes cells must move against the concentration gradient– From areas of low concentration to areas of high – This requires the cell’s energy – Done by transport proteins called “pumps” – Larger molecules can also be transported across the membrane by endocytosis and exocytosis Active Transport Lab • Background Information: Congo red is a biological dye, that diffuses easily into the cell, like water • This diffusion does not require energy • You are using yeast cells, that I woke up by adding water and sugar- they are currently alive … Lab Results 1. Macroscopically… which sample is darker? 2. Microscopically…. Which cells have absorbed the dye? 3. Are the (not boiled) yeast cells alive? 4. Are the boiled yeast cells alive? 5. Which cells moved the dye via active transport? 6. Of the cells that moved the dye…Did they move the dye in or out? 7. If active transport was used to move the dye, out via what mechanism did the dye get in? Endocytosis • Endocytosis is the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. The pocket that results breaks loose from the outer portion of the cell membrane and forms a vacuole within the cytoplasm. Large molecules, clumps of food, and even whole cells can be taken up in this way. Two examples of endocytosis are phagocytosis (fagoh-sy-TOH-sis) and pinocytosis. Phagocytosis • Phagocytosis means “cell eating.” In phagocytosis, extensions of cytoplasm surround a particle and package it within a food vacuole. The cell then engulfs it. Amoebas use this method of taking in food. Engulfing material in this way requires a considerable amount of energy and, therefore, is correctly considered a form of active transport. PINOCYTOSIS/ EXOCYTOSIS • In a process similar to endocytosis, many cells take up liquid from the surrounding environment. Tiny pockets form along the cell membrane, fill with liquid, and pinch off to form vacuoles within the cell. This process is known as pinocytosis. • Many cells also release large amounts of material from the cell, a process known as exocytosis (ek-soh-sy-TOH-sis). During exocytosis, the membrane of the vacuole surrounding the material fuses with