NYSED Part D Lab Review

Diffusion and OsmosisDesigned to help you understand the concepts of Diffusion and Osmosis and how these cell processes effect the cell;

Define: diffusion, osmosis, hypertonic, isotonic, hypotonic, saline, selectively permeable, molecule size;

Part 1: Diffusion Through a MembraneDiffusion: movement of molecules from an area of high concentration to an area of low concentration along the concentration gradient.

Example is when you put your Lugols solution into the water and the water began to turn the rust/tea color.Before diffusion occursAfter diffusion occurs

Initial State: Create a cellA starch and glucose solution is placed in a plastic bagLugols iodine solution is placed in the beakerLugols iodine solution is naturally a golden brown color. It turns a bluish black color when starch is added.The bag is tied offThe bag is placed in the beakerIodine solution (I)Glucose solution (G)Starch solution (S)

Final State: After sitting for 20 minutesNote the color changes in the bag and the beaker from the initial stateSSSSSSIIIIIIIIGGGWhat happened to the glucose in the cell? the starch in the cell? the Lugols iodine outside the cell? Why?

Prepare a wet mount slide of the inner epidermis (skin) of a red onion section;Observe the red onion and draw/label what you see;Add a couple of drops of saline (salt) solution to the epidermis. Wait 5 minutes;Observe under microscope again, note any changes;Add freshwater to the slide, wait 5 minutes, observe changes again.Part 2: Diffusion of Water Across a Membrane (Osmosis)

Red Onion Plasmolysis ObservationBefore and after observations of red onion epidermis under the microscope (400X)Red onion under in isotonic (normal) solution. Note cell membrane and cytoplasm almost completely fill the boundary of the cell wall.Red onion under in hypertonic (salt) solution. Water flows out from the cytoplasm, which reduces the volume of the cytoplasm. Like a balloon deflating inside a box, the plasma membrane pulls back from the cell wall in a process called plasmolysis.First drawingSecond drawingCell wallCell membranecytoplasm

Look what happens to a cell when you add distilled waterThese are cells from a red onion. They are suspended in distilled (pure) water, which is greater in concentration on the outside than the inside of the onion cell. The nuclei are prominent in the bottom cells, and the nucleoli are visible as dark areas inside the nucleus. In the cells of the right picture, the red pigment fills the cytoplasm, and internal structures aren't as visible.

Third drawing

Concepts You Must KnowThe baggie is the "cell and the plastic represents the cell membraneDiffusion moves material from high to low concentration, spending no energyOnly small molecules will go through the membrane...(starch can not). Starch WILL NOT diffuse out of the cell because it is too big and not permeableIodine (starch indicator) is in water in beaker (outside the cell)Benedict's solution tests for sugar...heat it and it turns red (positive for glucose)Water is used as a control for the indicatorsIodine or Lugols solution tests for starch...turns blue / black in starchThe "cell" should turn blue/black indicating that the iodine diffused into the "cell" and detected the presence of starch inside the "cell'Test the water outside the "cell" for glucose...Benedict's will turn red after heating if it detects the presence of glucose outside the "cell'. The diffusion of water is osmosis

Diffusion Lab Practice questions:1) C2) C3) B4) A5) BBLUE-BLACK 7) C8) B9) AD

Homework: Transfer your complete answers and drawings from the rough version of the NYS lab to the FINAL copy. All answers should be NEATLY transferred and diagrams colored (red) and labelled.

RB answers: pgs 7-10 #s 20-35.

20) 4 21) receptors22) 2 23) 4 24) 425) 2 26) 327) 4 28) 129) 230) 1 31) 232) 333) 334) 335) 1

Transport Test Monday (after the break)NYS Diffusion labTransport notes & regents practice questionsReview book pgs 7-10 Castle Cell membrane review assignment

The FINAL version of the NYS Lab is also due. All answers should be NEATLY transferred and diagrams colored (red) and labelled.

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