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Cellular Organization

Investigation 3 – Lab

 

 

 

 

 

 

 

MINDSET

This Investigation is designed to:

  • reinforce microscope operation and preparation of a wet mount slide,
  • aid you in identifying common structures of plant cells including chloroplasts, cell walls, cell membranes and nuclei,
  • aid you in comparing structures and organization of plant cells and tissues to those of animal cells and tissues,
  • help you understand that although generalizations about cellular structures of plant and animal cells can be made, all cells from the same organism may not have identical cellular structures or organelles, and
  • help you understand that the presence or absence of some cellular structures governs cellular and tissue function

BE PREPARED

Student Preparation for the Investigation includes having students gather the following materials. This preparation takes place on lab day after student lab groups have settled at their assigned lab tables.

Note: The materials are listed in students’ SDRs. They are also listed below for your reference.

  • (1) microscope
  • (1) plastic dropper
  • (1) forceps
  • (1) glass slide
  • (1) coverslip
  • (1) paper towel
  • (1) section of onion
  • (1) human cheek cell slide
  • (1) human blood smear slide
  • (1) Elodea leaf slide
  • (1) large intestine slide (human colon)
  • (1) Elodea stem slide
  • (1) sheet of lens tissue
  • (1) 100 ml beaker with 50 ml of water.

Direct one student from each lab group to collect the materials listed in their SDRs.

INVESTIGATE

  • Perform a mental review of the parts of an animal cell and a plant cell. Include the cell wall, cell membrane, cytoplasm, nucleus, and chloroplasts. Sketch an animal cell and a plant cell on the board if necessary. You should understand that plant cells have cell walls and chloroplasts, while animal cells do not.
  • Reflect on the PreLab video as you move through the procedural steps.
  • During the Experiment, every procedural step is important. If one step is skipped, data can become invalid. To help you keep on track, read each step thoroughly, complete the step, then check it off (Read it – Do it – Check it).
  • Complete all of the procedural steps in your SDR.

Note: The procedural steps are listed below for your reference. 

  1. Peel a very thin layer of onion off your section. The sample must be very thin so that it is only one layer of cells.
  2. Create a wet mount slide of an onion. Refer to the procedure to the procedure, Wet Mount Slide Preparation.
  3. Observe the onion slide under the microscope. Refer to the procedure, Microscope Use and Operation, if you need help. You may be able to more easily view the cells near the edge of your sample. The edges are likely to be thinner than the center of the specimen.

Note: Do not use the 100X oil immersion objective with wet mount slides. You may use the 100X objective with prepared slides, because they are sealed so the oil cannot go under the coverslip.

  1. Look for the cell structures listed in Table A.
  2. Record: As you see and identify the structures, place a check in the appropriate column of Table A.
  3. Record: Write any general observations about the slide in the last column of Table A.
  4. Observe each of the other prepared slides listed in Table A under the microscope.
  5. Record: Identify the structures and write your observations for each slide in Table A.

 

CLEAN UP

Clean up your bench after you have completed your investigations.