Chapter 2Cell As A Basic Unit Of

Life

What Is The Basic Unit Of All Living Things?

Cell is the basic unit of life

Click the arrow to view the cell anatomy

Light Microscope&

It’s Function

How To Set UpA

Light Microscope

Step 1: Carefully take the microscope out of its closet and place it on your lab bench. Carefully means using 2 hands, 1 underneath and the other holding the neck of the body. Take off the protective cover (For the lens).Step 2: Gently place the slide to be observed on the stage and hold it in place using the metal clips. The subject on the slide (usually in the middle) needs to be directly over the hole in the stage.Step 3: After placing the slide on the stage , look on the outside and use the rough/fine focusing knob to bring the slide as close to the objective as possible without touching it. Step 4: Now you may look in the eyepiece and slowly adjusting the focusing knob until the image become clear.

Note : When something comes into view, you need to verify that it is really something on the slide and not just a piece of dust on or inside the microscope. To test this, gently move the slide back and forth while looking into the eyepiece. If the image moves then, yes, you are looking at the slide. If nothing in the image moves as you move the slide, then, no, you are not looking at the slide but rather at some impurity.

Human Cheek CellsExperiment

Materials RequiredGlass microscope slidesPlastic cover slipsPaper towels or tissueMethylene Blue solution (0.5% to 1% (mix approximately 1 part stock solution with 4 parts of water))Plastic pipette or dropperSterile, individually packed cotton swabs

Methods1. Take a clean cotton swab and gently scrape the inside of your mouth.2. Smear the cotton swab on the centre of the microscope slide for 2 to 3 seconds.3. Add a drop of methylene blue solution and place a coverslip on top. Concentrated methylene blue is toxic if ingested. Wear gloves and do NOT allow children to handle methylene blue solution or have access to the bottle of solution.4. Remove any excess solution by allowing a paper towel to touch one side of the coverslip.5. Place the slide on the microscope, with 4 x or 10 x objective in position and find a cell. Then view at higher magnification.

• Methylene blue stains negatively charged molecules in the cell, including DNA and RNA. This dye is toxic when ingested and it causes irritation when in contact with the skin and eyes.• The cells seen are squamous epithelial cells from the outer epithelial layer of the mouth. The small blue dots are bacteria from our teeth and mouth.

How To PrepareAn

Onion Cell Slide

Method1. Take a small piece of onion and using forceps (tweezers) peel off the membrane from

the underside (the rough side).2. Lay the membrane flat on the surface of a clean glass slide, and then add one drop of

dye (iodine or methylene blue). Be very careful; these dyes will stain your skin and clothes.

3. Using a pin, lower a thin glass cover slip onto the slide. Make sure there are no air bubbles.

4. Put the slide onto the stage of the microscope. Make sure the objective lens is set on low power, and the microscope light is turned on.

5. Look through the eyepiece lens and turn the focusing wheel until you can see the cells. They should look like lizard skin.

6. Swap the objective lens for a high powered one so that you can see the cells at a greater magnification. You should be able to make out the nucleus.

ComparingAnimal Cell

&Plant Cell

Unicellular Organism

• Made up of one cell only. ‘Uni’ means one.• A simple organism.• Mostly are aquatic living things (in ponds, drains and the sea).• Carry out life processes inside the cell.• Do not have circulatory system.• Absorbs nutrients, expel wastes and exchange gas with their environment.• Also known as microorganism (microbe).• Asexual reproduction (Fission).

Examples : Paramecium, Amoeba, yeast, Pleurococcus, Chlamydomonas.

Human Cell Types

Cell Organization

Definition : Cell organization is the grouping of simple cell into more complex structures

Why Human Is Special?• Human are able to reflect to their act.• Only humans make moral judgements and moral choices.