card
102

cell

OLogy Series
biology
card
102

cell

OLogy Series
biology

Have you ever wondered what our muscles, blood, bones, and bodies are made of? They are made of cells! Cells are the building blocks of all life. Some living things, such as protozoa, are made of only one cell. The human body, on the other hand, contains trillions of cells. The cell's nucleus is the control center of all genetic information.

Hooked on Biology
The first person to observe cells was Robert Hooke. In 1665, this English scientist used a crude, homemade microscope to study objects like thin pieces of cork. He came up with the word "cell" because the little rectangles he saw reminded him of the small spaces where monks live in a monastery. Two centuries passed before scientists realized the importance of Hooke's observations.

What parts of your body are NOT made of living cells?

hair and nails

muscles and bones

ears and nose

Are you right?

Correct!

Your hair and nails are made up of stuff called protein, not cells. That's why it doesn't hurt when you cut them.

How long are the nerve cells in a giraffe's neck?

about one inch

about one foot

about ten feet

Are you right?

Correct!

Among the largest cells in nature, the nerve cells in a giraffe's neck can be about ten feet long. Boy, is that stretching it!

All cells are round.

Fact
or
Fiction
?

Fiction

Some cells are round, but they come in many shapes and sizes depending on what they do and where they are. Plant cells, for example, can be rectangular.

Your bones are made of hardened, dead cells.

Fact
or
Fiction
?

Fiction

Not at all; in fact, they are pretty lively. That's why if you break a bone, it heals in a couple of weeks.

cell
Contains: chromosomes, genes, and DNA
Size: from several feet long to 1/100th the size of the dot above this letter "i"
Made of: water, proteins, fat, sugar, and DNA
Reproduction: before cells divide they make a copy of their DNA, so two new cells have identical
copies of the DNA
Why important: makes up all living things

Image credits: Kelvin Chan.