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Kind of like a post office making sure each package

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Unformatted text preview: - Kind of like a post office, making sure each package goes to the right place-chloroplasts- – Found only in plants – Site of photosynthesis – Captures energy from sunlight & stores it as sugar-endoplasmic reticulum (smooth, rough)- Smooth ER- Detoxifies drugs- Synthesizes lipids (e.g. steroid hormones made from cholesterol)- Rough ER- Studded with ribosomes (“rough”)- More on ribosomes in ch. 12 Produces proteins- cilia & flagella = extensions of the plasma membrane that can move- Cilia usually moves fluid past- A flagellum usually propels a cell Chapter 5: Plasma membrane: functions, components- Plasma Membrane Functions :- Isolate cell contents (phospholipids)- Proteins: o Regulate exchange of substances o Communicate between cells o Create attachments with other cells o Regulate biochemical reactions- Phospholipid bilayer- The phospholipid bilayer o A phospholipid has a hydrophilic head and hydrophobic tails (fatty acids)- 2 movement types: passive & energy-requiring- Passive transport includes simple diffusion, facilitated diffusion, and osmosis- Energy-requiring transport includes active transport, endocytosis, and exocytosis- 3 types passive, 3 types energy-requiring- Passive: Simple diffusion : substances move down a concentration gradient (high to low) across a membrane o Molecules that move by simple diffusion include oxygen, carbon dioxide, and lipophilic molecules (e.g. alcohol, vitamins A, D, and E) Isotonic, hypertonic, & hypotonic solutions Facilitated diffusion : small molecules (e.g. salts, amino acids, sugars) diffuse down a concentration gradient with the help of a transport protein (channel or carrier) Specialized channel proteins called aquaporins are selective for water molecules Osmosis = diffusion of water across membranes Water diffuses from a region of high to low water concentration across a membrane Another way of saying that: water moves from a region of low solute (e.g. salt) to high solute to dilute it & reach equilibrium- Energy: Active transport : membrane proteins use energy (ATP) to move molecules across plasma membranes against their concentration gradients – Active transport proteins span the entire membrane – They often have a molecule binding site (recognition site) & ATP binding site – When the high energy of ATP is released, the protein changes shape: moves molecules against gradients – Active transport proteins are often referred to as pumps 3 types of endocytosis – Pinocytosis -(“cell drinking”) moves liquids into the cell – Receptor-mediated endocytosis- moves specific molecules into the cell – Phagocytosis- (“cell eating”) moves large particles into the cell Exocytosis moves material out of the cell – Cell uses energy to dispose of waste or secrete substances Vesicles containing the material move to the cell surface, fuse with the cell membrane, then allow contents to diffuse/empty into the outside fluid Diffusion vs. osmosis- which will occur & in which direction?...
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