All organisms are made of cells. Cells are very small, so large organisms contain millions of cells.
How many times can a good light microscope magnify?
1,500 times
All cells have a cell membrane around the outside. Inside the cell membrane is a jelly-like substance called cytoplasm, in which are found many small structures called organelles. The most obvious of these organelles is usually the nucleus.
The cell membrane is a very thin layer of protein and fat. It is very important to the cell because it controls what goes in and out of it. It is said to be partially permeable, which means that it will let some substances through but not others.
All plant cells are surrounded by a cell wall made mainly of cellulose. This helps to protect and support the cell. Large molecules are able to go through the cellulose cell wall. It is therefore said to be fully permeable.
Cytoplasm is a clear jelly. It is nearly all water; about 70% is water in many cells. It contains many substances dissolved in it.
Some animal cells have granules (tiny grains) of another substance similar to starch, called glycogen. These granules are found in the cytoplasm.
The nucleus is where the genetic infomation is stored.
A comparison of plant and animal cells. Fill in the blank //plant cells
A) cell membrane
B) chlorophyll
C) large
D) cell sap
E) starch grains
F) regular
A comparison of plant and animal cells. Fill in the blank //animal cells
A) small vacuoles
B) glycogen
C) granules
D) irregular
Glycogen is a reserve fuel. When required, it can be broken down to glucose.
Cells like mitochondria and ribosomes, are so small that we need a very small unit in which to measure them. The most useful one is the micrometre, symbol μm.
