Biology Lab Exercise 5 Vocabulary

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Exercise 5

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Cell Structure and Membrane Function

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Introduction

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The structure of cellular components reflects adapations to accomplish those functions necessary for life. The collective functions of individual cells allow for the activity and behavior of the entire organism of which those cells are a part. In this exercise, you will use a compound microscope to look at cells and observe some cellular activity. You will also conduct experiments illustrating some of the mechanisms of cellular transport.

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Part A

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Cellular Transport

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Passive Transport

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Involves the movement of water or solutes through a semi-permeable membrane down their concentration gradient.Does not require cellular energy in the form of ATP. Includes simple and facilitated diffusion and osmosis.

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Active Transport

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Involves the movement of solutes through a semi-permeable membrane against their concentration gradient. Requires cellular energy in the form of ATP. Requires membrane transport proteins.

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Concentration Gradient

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Regions of higher concentration of water or solutes to regions of lower concentration

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Simple Diffusion

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Where no membrane transport proteins are required.

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Facilitated Diffusion

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Where membrane transport proteins are required.

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Osmosis

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Is specific to the passive transport of water from an area of higher water potential to an area of lower water potential (lower concentration to higher concentration of solutes). Water moves through protein channels called aquaporins.

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Tonicity

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The ability of a solution to cause a cell to gain or lose water.

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Hypotonic

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Solutions containing less solutes by % (more water).

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Hypertonic

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Solutions containing more solutes by % (less water).

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Net Movement of Water

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Molecules will move from regions of high water concentration (hypotonic solution) to regions of lower water concentration (hypertonic solution).

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Isotonic

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Equal to one another in solution concentration.

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Part A-1

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Passive Transport in a Model Cell

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Dialysis

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The process of separating crystalloids and colloids in solution by the difference in their rates of diffusion through a semipermeable membrane, crystalloids pass through readily, colloids very slowly or not at all.

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Semi-Permeable Membrane

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A membrane that is selectively permeable, i.e. being permeable to only certain molecules and not to all molecules.

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Cytoplasm

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The contents of the cell, exclusive of the necleus and bounded by the plasma membrane

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Extra-Cellular Fluid

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The body fluid outside the cell composed of blood plasma, interstitial fluid, lymph and transcellular fluid.

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% Mass Change of Bag

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Change in Mass of Bag/ Initial Mass of Bag X 100

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Results of "Model Cell" Experiment

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1. Starch - Stayed Inside
2. Dextrose - Stayed Inside
3. Water - Moved Inside (the bag was heavier at end)
4. IKI - Moved Inside (the starch turned black on the inside of the bag)

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Part A-2

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Osmosis in Elodea

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Procedure for Creating Wet Mount

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1. Obtain a clean glass slide and coverslip.
2. Place one or two drops of water on the slide.
3. Obtain specimen and prepare as needed.
4. Place specimen in water.
5. Carefully position the coverslip by placeing one edge of it down first and then lowering the other side. Try to minimize the number of air bubbles that form.
6. The coverslip should not be floating on the slide. If it does, remove the coverslip and excess water and start over.

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Procedure for Replacement Staining Technique

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1. Place a few drops of IKI on the slide against one edge of the coverslip.
2. Place the smooth edge of a single layer of paper towel up against the opposite edge of the coverslip. The paper towel will pull the water out from under the coverslip and the stain (IKI) will replace the water.
3. Continue the process, adding more IKI if necessary, until the stain covers the area under the coverslip.
4. Wait a few minutes and then place distilled water on one side of the coverslip and draw the excess IKI out with the paper towel. The water then replaces the IKI.
5. Once all the yellow IKI has been removed, dry the upper surfaces of the slide.

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Osmosis

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Is specific to the passive transport of water from an area of higher water potential to an area of lower water potential (lower concentration to higher concentration of solutes). Water moves through protein channels called aquaporins.

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Cytoplasmic Streaming
(Cyclosis)

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A circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials within cells.

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Plasmolysis

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A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.

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Turgid

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Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a greater solute concentration than its surroundings, resulting in entry of water.

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Part A-3

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Osmoregulation in Protists (Protozoans)

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Hypotonic

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Referring to a solution that, when surrounding a cell, will cause the cell to take up water.

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Osmosis

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Is specific to the passive transport of water from an area of higher water potential to an area of lower water potential (lower concentration to higher concentration of solutes). Water moves through protein channels called aquaporins.

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Contractile Vacuoles

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A membranous sac that helps move excess water out of certain freshwater protists.

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Part A-4

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Active Transport of Yeast

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Denaturation
(Denatured)

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Of, or pertaining to, a molecule (such as a protein or a nucleic acid) wherein its chemical structure is altered through chemical or physical means so that some of its original properties are lost or diminished.

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Congo Red

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An odourless, dark red or reddish brown powder which decomposes on exposure to acid fumes. It is used as a diagnostic aid in amyloidosis, and has been used as an antihemolytic and detoxicant.

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Result of Active Transport in Yeast

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Unheated yeast did both passive and active transport and did not take in the congo red dye. Heat-treated yeast only did passive transport and did take in the dye.

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Part B

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Structure and Movement in Protists

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Protist

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An informal term applied to any eukaryote that is not a plant, animal, or fungus. Most of them are unicellular, though some are colonial or multicellular.

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Pseudopodium
(plural, Pseudopodia)

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Extention of cytoplasm used for mobility in amoeba.

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Cilium
(plural, Cilia)

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Fine hair-like structures covering the cell membrane used for mobility in paramecium and similar organsims.

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Flagellum
(plural, Flagella)

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Long, slender, threadlike, whiplike extension used for mobility in Euglena.

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Protista

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The kingdom of eukaryotic unicellular organisms such as Euglena, Paramecium, and Amoeba