Synthesizes lipids eg steroid hormones made from

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- 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
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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? Osmosis vs. diffusion: which one will happen?
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