Microscope, Cells, and Organelles Lab

Part One: The Microscope

                                      Lens mag.                             Ocular mag.            Total mag.

a.  Scanning                        4x          multiplied by      10x         =             40x

b.  Low Power                   10x         multiplied by      10x         =             100x

c.  High Power                   40x         multiplied by      10x         =             400x

d.  Oil Immersion              100x       multiplied by      10x         =             1000x

Part Two: The Virtual Microscope

Onion Root Under High Power (mag. 400x)

Three visible structures are the nucleus, the plasma membrane, and the nuclear membrane. Take a closer look!

Onion Root Under Oil Immersion (mag 1000x)

The plasma membrane is the rectangular shape,  and the nucleus is the dark part in the middle that is surrounded by the nuclear membrane. Here's a different slide-

Cheek Cells Under High Power (mag. 400x)

Here, we can see the cell membrane and nucleus, as well as cytoplasm (that light blue stuff inside the cell), and some darker area within the cytoplasm that are organelles. The darkest ares of the nucleus are the nucleoli.

1) The nuclear membrane separates the contents of the nucleus from the cytoplasm.

2)The nucleoli produce protein and RNA, which are the components of ribosomes. These ribosomes produce specific proteins that are the enzymes, transporters, etc that the cell needs to do virtually anything.

3) A nucleus also contains DNA, RNA, and ribosomes.

4) The lowest powered objective lens should be in place when you start.

5)When you first begin looking at a slide, you use the rough focus knob.

6) If you see two overlapping circles, you must adjust your oculars.

7)The mechanical stage moves the slide and the x and y knobs help you to adjust precisely.

8) The reastat and the iris diaphragm adjustment knob both control light.

9) Oil immersion is the highest magnifying objective.

10) Scanning allows you to see the largest area of the object you are viewing.

Part 3: When Bad Things Happen To Good Carrots

Before

 

After 24 Hours

	Length @ Start of 24 Hours	Length @ End of 24 Hours	Width @ Start of 24 Hours	Width @ End of 24 Hours
Fresh Water Carrot	2”	2”	¾”	¾”
Saltwater Carrot	2”	1 9/10”	5/8”	½”

  

At the beginning of the experiment, I predicted that the saltwater carrot would shrink, and that the solution would turn more orange. I believed this because the principles of osmosis state that water molecules will move towards an area of less concentration, and by adding a solute such as saltwater to a solution, we decrease the concentration of water molecules near the cell (carrot). Therefore, the water will move out of the cell, possibly taking some orange dye with it. This would decrease the width and length of the carrot piece.

I was correct in my prediction that the saltwater carrot would shrink (it did). The freshwater carrot stayed the same size. In addition, the saltwater carrot became very limp while the freshwater carrot stayed crisp. The string around the saltwater carrot became looser and the freshwater carrot remained tight. This indicates to me that osmosis occurred in the saltwater carrot, where water molecules diffused into the saltwater solution and out of the cells, decreasing cell size. Because there were no changes in size in the freshwater carrot, I would surmise that the concentration of water inside and outside the cells was approximately equal. However, the freshwater carrot solution did turn more orange, whereas the saltwater solution stayed clear (contrary to my prediction), which may mean that the orange in carrots tends to diffuse along its concentration gradient.

Osmosis is the diffusion of water across a selectively permeable membrane. Water molecules diffuse towards its region of lower concentration across the membrane. Solutes such as glucose cannot necessarily cross the membrane, and so their presence on one side lessens the concentration of water molecules. This is where the water will go, until pressure against the membrane (osmotic pressure) builds to the point it counteracts the osmosis of water molecules. This is an important way for cells to maintain a healthy pressure as well as maintaining an appropriate amount of H2O in the cells, a molecule that is both created and used by cells in a myriad of ways. If too much has accumulated inside the cell, it will leak out, and if there is too little inside, it will diffuse in.