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ELODEA MEMBRANĘ TRANSPORT LAB

Background

In order for cells to maintain the Chemical reactions occurring inside themselves substances must move back and forth between a cell s external and internal environments. Morę specifically, reactants need to be acquired by the celi while harmful products must be eliminated. For example, during respiration your cells must acquire oxygen and must eliminate carbon dioxide. Other products, like ATP (an energy molecule) are beneficial and are used by the celi.

As you know, the celi membranę is a fluid structure composed of phospholipids, cholesterol, and various membranę proteins (adhesion, recognition, receptor, and transport). The precise location through which a substance travels is dependent on two important molecular characteristics; the molecule size and charge (polarity). In generał, smali uncharged (non-polar) substances move through the lipid portion of the membranę, while smali charged (polar) and larger molecules must enter the celi through proteins.

In most instances, the movement of substances requires the existence of a concentration gradient across the celi membranę and substances move from areas of higher concentration to areas of lower concentration. In such situations, substances will move by osmosis, diffusion, or passive diffusion (facilitated diffusion). When substances require movement against their concentration gradient active transport is used.

In the following laboratory exercise you will investigate the movement of substances into and/or out of the membranę of an elodea leaf in order to gain a greater understanding of processes of osmosis and diffusion.

Objective

1. You should understand how and why water moves through a semi-permeable membranę in various liquid environments.

Materials

1 Elodea Leaf soaked in Distilled Water 1 Elodea Lead soaked in Saltwater Compound Light Microscope 1 Microscope Slide 1 Cover Slip