1. Find your science journal

2. What is a cell?
A cell is the very smallest unit of living matter. All living things including plants and animals are made up of cells.

3. What is a cell made of?
Cells are made of atoms, which are the smallest units of matter.

4. How many different types of cells are there?
There are many different kinds of cells. The two kinds you may already be familiar with are animal and plant cells.

5. What makes plant cells different from animal cells?
One main difference is that plant cells contain chloroplasts which contain chlorophyll. Another difference is that plant cells have a rigid cell wall while animal cells have a flexible cell membrane.

6. Is there anything inside an animal cell?
Cells are tiny, but they have lots of important parts inside! These different parts are called organelles – because they are like our organs but smaller!

7. What different organelles make up an animal cell?
One part found in all cells is the cell membrane. The cell membrane surrounds the cell, holds the other parts of the cell in place, and protects the cell.

8. Inside the membrane, all cells, except for bacterial cells, contain a nucleus and cytoplasm. The nucleus is a dark structure located in the middle of the cell. It controls the cell's activities, and acts like the cell's brain. Inside the nucleus there is DNA which contains genetic information.

9. The cytoplasm is a jelly-like substance inside the cell where most of the cell's activities take place. It's made out of water and other chemicals. All cell parts, except the nucleus, are located in the cytoplasm

10. Like all living things, cells die
Like all living things, cells die. If you watched a clock for one minute, about three billion cells in your body die.
The length of time cells live can vary. For example, white blood cells only live for thirteen days, red blood cells live for about one hundred and twenty days, liver cells live about eighteen months, and nerve cells can live up to one hundred years. That is a very big difference!

11. How do I get new cells when the old ones die?
Basically, each cell is made from an already existing cell. New cells are made through a process called cell division or mitosis. One cell turns into two cells and then each of those two cells turn into four cells, etc. Even humans started life with only one cell.

12. How do I get new cells when the old ones die?
Most of the cells in multi-celled organisms use mitosis to reproduce. The animation shows the basic steps in mitosis which are:
1) At the start of mitosis chromosomes are in the nucleus.
2) The chromosomes in the nucleus will then make a copy of themselves
3) Next the cell divides.
4) Lastly, one set of chromosomes goes to the new cell and one set remains in the parent cell.

13. Organisms like humans are made up of trillions of cells
Organisms like humans are made up of trillions of cells. There are also one celled organisms such as euglenas, amoebas, and bacteria.

14. If cells are so tiny, how do scientists study them?
One of the most important tools that scientists use to study cells is the microscope. An optical microscope can magnify a cell up to two hundred thousand times. If an ant were to be magnified at two hundred thousand times, it would be more than two and one half miles long. Scientists also put dyes in cells to make certain parts look bright under a microscope.

15. Do all cells inside me look the same?
No, different cells have different jobs. Cells with different jobs can look very different.
All cells start as stem cells. Once they are ‘assigned’ a job, they change to fit their purpose.

16. Blood Cells
Skin Cells
Nerve Cells

17. Immune Cells Attack Cancer Cell
Cancer is caused by cells that don’t duplicate correctly. Cells in our immune system will try to kill the bad cells.
Immune Cells Attack Cancer Cell

19. Let’s Review What are some differences between animal and plant cells?

20. Sketch a diagram of a plant and animal cell in your journal
Sketch a diagram of a plant and animal cell in your journal. What are 2 things they have in common? What are 2 main differences?
Plant Cell