Building blocks of life (cells)

1. The Cell Theory states that cells are the basic units of life, and that cells come from other cells. Cells got their name from an Englishman named Robert Hooke in the year 1665. He first saw and named "cells" while he was experimenting with a new instrument we now call a "microscope. For his experiment he cut very thin slices from cork. He looked at these slices under a microscope. He saw tiny box-like shapes. These tiny boxes reminded him of the plain small rooms that monks (монахи) lived in called "cells".

2. All living beings are made up of cells. Some of them are made up of only one cell and others have many cells. Sometimes people think of cells as a balloon filled with fluid (жидкость, газ). That is not really true because a balloon does not let things move in and out like the membrane of a cell. It is important for cells to be able to move materials in and out of the cell. Cells are amazing. They are all made of similar building blocks, but they do many different things depending on how they are programmed.

3. Prokaryotic cells have no nucleus or organelles enclosed within membranes. Eukaryotic cells have a nucleus and organelles that are surrounded by membranes. Each organelle does a specific cell function. Individual protists (протисты, простейшие) have only one cell, while plants and animals can have trillions of cells.

4. The adult human body is made up of about 37 trillion cells. If you lined up all the cells of an average human, end to end, the line could circle the earth almost 19 times! Complex creatures like humans have special cells for special functions like carrying oxygen around the body, digesting food, or making bone. Other cells defend us against invading (вторга́ющиеся) bacteria and viruses. There are cells that transmit signals through out the body like the signals from your eyes to your brain while reading this article. There are hundreds of jobs that cells can do.


Comment on how many different types of cells does the average human body have ?

a)20
b)200
c)400
d)1000