Introduction to Cells Smallest Units of Life

What are cells? Cells are the smallest structural and functional units of life.

Your Body Has 90 Trillions Cells That's a 90 followed by 12 zeros.

Form Follows Function The shape of a cell depends on what the cell does. Muscle cells are different than bone cells.

Plant Cells Plant cells have flat sides and are green because of a chlorophyll (pigment).

Animal Cells Animal Cells are generally pictured as round but they could be other irregular shapes.

What’s inside of cells? Cells contain structures called “organelles” which means little organs.

Nucleus The most important organelle because it contains DNA (genetic information).

Eukaryotic Cells Eukaryotic Cells have a Nucleus. Example-Plants and Animals

Prokaryotic Cells Prokaryotic Cells like Bacteria do not have a Nucleus.

Cell Size Cells can’t get too big or they will break like a water balloon.

Who discovered cells? Robert Hooke discovered cells looking at cork under a microscope hundreds of years ago.

How are cells viewed? Cells are generally viewed with a compound microscope that has 2 or more lenses.

Microscopes Resolution-makes images clearer Magnification-makes object bigger.

The modern microscope Stage-where you put the slide. Objectives-magnify image

Microscope lens Microscope lenses are convex. This means that they are curved outward like a fish eye.

Levels of Organization Cells form tissues which then form organs.

Scanning Electron Microscope An SEM is one of the most powerful kinds of microscopes.

Single Celled Organisms Some organisms like these bacteria are made of only one cell.

Cell Theory All living things are made of cells. Cells are the basic structural and functional units of life. All cells come from other cells.

Thanks for your attention! Study hard for the test!

Review Questions

1. What are cells?

2. Who discovered cells?

3. What are the parts inside a cell called?

4. Why is the nucleus important to cells?

5. How are plants cells different from animal cells?

6. What would happen if cells get too big?

7. What is an Eukaryotic cell?

8. How many cells do people have?

9. How do people look at cells?

10. True or False. All cells come from other cells.

11. Form follows __________.

12. True or False. Bacteria are single celled organisms.