Cell structure

Eukaryotes and prokaryotes

• Animal or plant cells

• Genetic material enclosed in nucleus

  Prokaryotes

  • Contains extra rings of DNA called plasmids

  • Cell wall doesnt contain cellulose

  • Bacteria cells

What is the nucleus ?

Contains genetic information that controls all of the activities in the cell

Why is a thin layer of onion epidermis used ?

Ti help see individual cells

What is the cytoplasm ?

A gel like substance where the chemical reactions take place. Also contains enzymes that help control the chemical reactions.

What is the mitochondria ?

Where aerobic respiration takes place providing all of the energy needed for the cell.

What is the ribosomes ?

Where protein synthesis takes place

What is the vacuole?

contains cell sap which is a weak solution of sugars and salts. Also gives strength to the cell

Cell wall

Contains cellulose and holds the cell together

Chloroplasts

Where photosynthesis takes place. Also contains a green substance called chlorophyll which absorbs all the light needed for photosynthesis

How do you set up your slide when viewing your onion cell?

• Add a drop of water to the middle of a clean slide

• Then cut up an onion and seperate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers.

• Using the same tweezers place the epidermal tissue in the water on the slide

• you then add a drop of iodine solution. This is a stain used to highlight any objects by adding colour to them.

• Place a cover slip on top. To do this stand the cover slip upright next to the water droplet. Carefully tilt and lower it so it covers the specimen. Make sure you dont get any air bubbles underneath otherwise it will obstruct your view of the specimen.

How do you view your slide on a light microscope ?

• Place your slide on the stage

• Select the lowest powered objective lens

• Use the coarse adjustment knob to move the stage up until it is just below the objective lens.

• Look down at the eyepiece. Use the coarse adjustment knob to move the stage down until the image is roughly in focus.

• Adjust the focus with the fine adjustment knob until the image is roughly in focus.

How do you draw your observations of a onion cell?

• Label any subcellular structures

• No colouring or shading

• Include a title of what you are observing

• The magnification