Honors Biology Cell transport

Transfer of materials Passive transport: Diffusion & Osmosis Facilitated transport Active transport

Cell Membrane (review slide) Separates inside of cell from surroundings Controls the passage of substances into and out of the cell “lipid bilayer” made of 2 layers of fats (lipids), with proteins imbedded in it. “selectively-permeable” : some types of substances (like water) can go through it. Fat layer Protein

(review slide)

Head region of the lipid are polar molecules so they are attracted to water Tails region of the lipid are nonpolar they repel water. These molecular properties form the separation of inside and outside the cell.

Not all molecules can pass through the membrane!

Diffusion: causes substances to move across the cell membrane but does not require the cell to use energy. Individual particles continuously move in random directions Substances move more frequently from an area of high concentration to an area of low concentration until equilibrium is reached.

Diffusion H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O Outside cellinside cell High Concentration Low Concentration Molecules are in constant motion they will continue to move until equilibrium is reached. Equilibrium ! Diffusion video: hill.com/sites/ /student_view0/chapt er2/animation__how_dif fusion_works.html hill.com/sites/ /student_view0/chapt er2/animation__how_dif fusion_works.html

Osmosis The diffusion of water across a semipermeable membrane is called osmosis. Water moves down its concentration gradient. From high concentration to low until equilibrium is reached. hill.com/sites/ /student_view0/chapter2/a nimation__how_osmosis_works.html hill.com/sites/ /student_view0/chapter2/a nimation__how_osmosis_works.html

Hypo vs Hyper tonic solutions Hypertonic solution: the concentration of solutes is higher on that side of the membrane (high) solute (low) water Hypotonic solution: the concentration of solutes is lower on that side of the membrane (low) solute (high) water Solute: substance (ex: sugar or salt) that is dissolved in water

membrane watersugar solution There are as many water molecules on the right as there are on the left but many of them are attached to sugar molecules and are not free to move. 6

Because there are more freely moving water molecules on the left, more diffuse through the pores of the membrane from left to right than from right to left. 7 Molecular movement

There is a greater concentration of free water molecules outside the cell than inside so water diffuses into the cell by osmosis and the cell swells up Osmosis in animal cells 11

Isotonic: the concentration of solutes is equal on both sides of the cell.

Points for intro of lab report Paragraph 1 Purpose: GSE: The movement of certain materials through the cell membrane is essential to chemical reactions which are required for the survival of living organisms. Specific to this lab: set up a model of a cell using dialysis tubing with sucrose solutions of varying concentrations. Measure the amount of osmosis by comparing the mass of the “cell” before and after it has soaked in water. Question: stated on lab handout Question: stated on lab handout

Paragraph 2 Definition of osmosis: diffusion of water Dynamic equilibrium: molecules continue to move, but in equal numbers in and out of cell In intro where is the high concentration of water versus the low concentration of water in our lab set up? Therefore where do you predict water will move? How does the varying sucrose affect the concentration of water inside the “cell”?

Paragraph 3 Use key phrases from Question: “rate of osmosis”, concentration of sucrose”, In hypothesis: will water move into or out of “cell”? How will the concentration of sucrose affect how much water will move? How will your measurements show this?

Conclusion paragraph #1 Restate question Restate hypothesis State Hypothesis WAS correct but provide specific examples from class data to illustrate your point. Describe graphed line which shows the trend in the data.

Conclusion paragraph #2 Discuss reasons for the differences in the change in mass Why calculate % change. Were all cells initially the same mass? Discuss this issue. Did the cells reach equilibrium? Why? Consider both water and sugar when answering this? Did the water reach dynamic equilibrium? Explain.

Conclusion paragraph #3 Strengths of dialysis tubing: selective permeability- explain Weakness of dialysis tubing: facilitated diffusion/active transport? O2 and CO2 see molecular workbench activity page 4 “diffusion, osmosis, active transport” osmosis-and-active-transporthttp://concord.org/stem-resources/diffusion- osmosis-and-active-transport Research Emphysema include citation

Conclusion paragraph #4 Sources of error: identify why all “cells” were not the same initial mass Ways to improve the experiment Extra/new topics related to this lab

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Describe how oxygen and carbon dioxide move into and out of the lungs and extremities. Page 4 molecular workbench “diffusion, osmosis, active transport”

Cells in hypertonic solutions lose water and shrivel. Cell’s activities are disrupted by lack of water.

Cells in hypotonic solutions gain water and swell. This can make animal cells burst. Plant cells do not burst because they are surrounded by a rigid cell wall hour time lapse after plant is watered.

Turgor pressure Turgid: swollen Turgor pressure the rigidity of plant cells when they contain enough water so that the cell membrane exerts pressure on the cell wall. Can tell turgor pressure is low when plant wilts.

Arnold/VLI/Module%202/m2cellfunctionandenergetics/m2cellfunctionandenergetic s6.html

“regular” “shriveled”“swollen”

Osmosis: the diffusion of water as seen in class. Size of a cell membrane can change as the amount of water inside changes in response to external conditions change. Cells surrounded by “plain water” Cells surrounded by “salt” water

Facilitated diffusion hill.com/sites/ /student_view0 /chapter2/animation__how_facilitated_dif fusion_works.html hill.com/sites/ /student_view0 /chapter2/animation__how_facilitated_dif fusion_works.html

Facilitated Diffusion Uses specific protein pores in the cell membrane to move certain “large” molecules from high concentration to low concentration.

Active Transport: cells can use energy to move materials in or out regardless of concentrations. Outside cellinside cell Protein Pore in cell membrane High Concentration Low Concentration HIGHER Concentration ATP= Energy required

Endocytosis: When the cell membrane folds around large amounts of materials to move it INTO the cell. Think amoeba eating Exocytosis: When the cell membrane folds around large amounts of materials to move it OUT of the cell. Simulation : hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/ /120068/bio02.swf::Endocytosis%20and%20Exocytosishttp://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/ /120068/bio02.swf::Endocytosis%20and%20Exocytosis

Study for test Topics Single celled organisms – Bacteria – Protists Diffusion Osmosis Passive transport Active transport Assignments to review Book study guide chapter 19 Bacteria and viruses Book study guide chapter 20 protists Protist lab: amoeba, paramecium, euglena Molecular work bench “diffusion questions” Textbook chapter review 7-3 Osmosis lab Constructed response: dialysis tubing with iodine and starch Class notes Chapter 19 Chapter 20 Chapter 7