BIOL 2160 Test 3

BIOL 2160 Test 3 - C hapter 6: I nteractions Between Cells...

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Chapter 6: Interactions Between Cells and the Extracellular Environment I. Extracellular Environment Extracellular Environment - The extracellular environment includes everything located outside the cells. - Cells receive nourishment from and release wastes into the extracellular environment. - Cells communicate with each other by secreting chemicals into the extracellular environment. Body Fluids - 67% of our water is within cells in the intracellular compartment . - 33% is in the extracellular compartment . Of this: o 20% is in blood plasma . o 80% makes up what is called interstitial fluid . ( Like cytoplasm but outside the cell ) Cell Transport - The plasma membrane is selectively permeable , meaning that it allows some molecules to cross but not others. o Generally not permeable to proteins, nucleic acids, or other large molecules o Generally permeable to ions, nutrients, and wastes Categories of Membrane Transport 1. Carrier-mediated : a. Facilitated diffusion b. Active transport 2. Non-carrier-mediated : a. Simple diffusion of lipid-soluble molecules b. Simple diffusion of water = osmosis c. Simple diffusion of ions through nonspecific channels - Passive transport Molecules move from higher to lower concentration without using energy. ( like laying around on couch and not using energy ) - Active transport Molecules move from lower to higher concentration using ATP. ( being active, working out, uses up energy ) o Requires energy II. Diffusion and Osmosis
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These are both PASSIVE transport processes… meaning they happen on their own AND don’t require additional energy (ATP) Diffusion - Solution consists of a solvent (water) and a solute (molecules dissolved in water) o Molecules in a solution are in a constant state of motion. o If there is a concentration difference between two regions, random motion will establish equilibrium via diffusion. - Fig. 6.3 Diffusion (a. net diffusion – one side higher concentration and other side lower concentration and b. no net diffusion – equal concentrations) - Fig. 6.4 Diffusion (glucose is small molecule that will go both inside and out to reach equilibrium) Diffusion Across the Plasma Membrane - Nonpolar (or uncharged) lipid-soluble molecules pass easily. o Oxygen, carbon dioxide, and steroid hormones - Fig. 6.5 Diffusion Across the Plasma Membrane (more oxygen outside cell then inside because blood carries oxygen…thus it’s gradient want it to move into the cell while in the cell from cellular respiration we have carbon dioxide - Charged ions can pass through ion channels that cross the plasma membrane. o Channels may always be open or be gated. - Fig. 6.6 Diffusion Across… (channels open or close) Rates of Diffusion - Depend on: o Magnitude of concentration difference (means the relative difference between the concentration on the inside of the cell verses the concentration on the outside of the cell) o Permeability of the membrane to the molecules o Temperature of the solution o Surface area of the membrane
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BIOL 2160 Test 3 - C hapter 6: I nteractions Between Cells...

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