Honors Biology

Cell transport

Transfer of materials

Passive transport: Diffusion & OsmosisFacilitated transportActive 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

Fat layerProtein

(review slide)

(review slide)

(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

H2O

H2OH2O

H2OH2O

H2O

Outside cell inside cell

High Concentration

Low Concentration

Molecules are in constant motion they will continue to move until equilibrium is reached.

Equilibrium !

Diffusion video: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_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.

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

https://sphotos-b.xx.fbcdn.net/hphotos-ash3/601094_534163219938027_72024092_n.jpg

Hypo vs Hyper tonic solutions

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

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

membranewater sugar 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 onthe left, more diffuse through the pores of the membrane from left to right than from right to left.

7

There is a greater concentration of free water molecules outside the cell than inside

so water diffuses into the cellby 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 2Definition of osmosis: diffusion of waterDynamic 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 questionRestate hypothesisState 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 #2Discuss reasons for the differences in

the change in massWhy 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” http://

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 experimentExtra/new topics related to this lab

http://ri-itest.portal.concord.org/preview

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.

http://www.botany.hawaii.edu/faculty/webb/bot311/bot311-00/plantcellwalls00/ColeusWilt57-600.jpg

http://www.youtube.com/watch?v=fNyYuVarTIQ 4 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.

http://legacy.hopkinsville.kctcs.edu/sitecore/instructors/Jason-Arnold/VLI/Module%202/m2cellfunctionandenergetics/m2cellfunctionandenergetics6.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

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_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 cell inside 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: http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio02.swf::Endocytosis%20and%20Exocytosis

Study for testTopics• 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