Bio Lab: Osmosis And Diffusion

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agar

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culture medium - gelatinous material

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dialysis

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the separation of dissolved substances by means of their unequal diffusion through a differentially permeable membrane.

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diffusion

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substances move through solutions and across membranes in a predictable direction

passive, directional movement of molecules

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hypotonic

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describes a solution with a lower concentration of solutes, especially those solutes that do not pass across the surrounding membrane.

water moves across semipermeable membranes out of hypotonic solutions

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isotonic

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refers to two solutions that have equal concentrations of solutes

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nonpolar molecule

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no local areas of positive or negative charge

can pass through membranes most easily

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plasmolysis

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shrinkage

(cytoplasm is no longer pressed against cell wall)

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random motion

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caused by heat

passively moves molecules in biological systems

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solution

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homogeneous liquid mixture of two or more kinds of molecules

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brownian movement

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small molecules move after collisions with moving molecules

originally described in 1827 by robert browning

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dialysis tubing

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good models of differentially permeable membranes because they have small pores that allow small molecules such as water molecules to pass

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hemolysis

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destruction of a red blood cell by the influx of water causing the cell to burse

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independent variable

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always graphed on the horizontal axis

variable that you have established and actively controlled

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lysis

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destruction of a cell by the influx of water causing the cell to burst

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osmosis

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diffusion of water across a differentially permeable membrane

follows the same laws as diffusion but always refers to water (the principle solvent in cells)

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polar molecule

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have positively charged areas and negatively charged areas

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solute

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a substance dissolved in a solution

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solvent

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a fluid that dissolves substances

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dependent variable

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always graphed on the vertical axis

variable changed in response to differences in the independent variable

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differentially permeable

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selectively permeability results from the basic structure of membranes

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hypertonic

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refers to a solution with a high concentration of solutes

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iodine

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a starch indicator that changes from yellow to dark blue in the presence of starch

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molecular weight

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sum of atomic weights of all atoms in a molecule

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pressure potential

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important component of water potential

a measure of the effect of pressure or tension on a substance's ability to absorb or release water

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solute potential

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the effect of dissolved substances in the water

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water potential

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the combined effects of concentration and pressure such as that from cell walls

water will flow from an area of high to an area of low