7.1 & 7.2: Microscopes, Cell Theory & The Plasma Membrane
Microscopes
There are two types of microscopes: compound and electron. A compound microscope consists of a series of glass lenses and uses light to produce a magnified image. An electron microscope uses magnets to shoot a beam of electrons at thin slices of cells. This allows for greater resolution.
Here is a diagram and explanation of the parts of a light microscope, which you will use in class.
Cell Theory
This is one of the fundamental ideas of modern biology and includes these three principles: (1) all living organisms are composed of one or more cells, (2) cells are the basic unit of structure and organization of all living organisms, and (3) cells arise from previously existing cells, with cells passing on copies of their genetic material to their daughter cells.
Cells
There are two basic kinds of cells: prokaryotes & eukaryotes. Prokaryotes do not have a nucleus, but eukaryotes do. They differ in their structures, but what they have in common is a plasma membrane. This is a boundary that controls what enters the cell and what leaves it.
There are two types of microscopes: compound and electron. A compound microscope consists of a series of glass lenses and uses light to produce a magnified image. An electron microscope uses magnets to shoot a beam of electrons at thin slices of cells. This allows for greater resolution.
Here is a diagram and explanation of the parts of a light microscope, which you will use in class.
Cell Theory
This is one of the fundamental ideas of modern biology and includes these three principles: (1) all living organisms are composed of one or more cells, (2) cells are the basic unit of structure and organization of all living organisms, and (3) cells arise from previously existing cells, with cells passing on copies of their genetic material to their daughter cells.
Cells
There are two basic kinds of cells: prokaryotes & eukaryotes. Prokaryotes do not have a nucleus, but eukaryotes do. They differ in their structures, but what they have in common is a plasma membrane. This is a boundary that controls what enters the cell and what leaves it.
Courtesy of Penn State's College of Science
The process of maintaining balance in an organism's internal environment is called homeostasis, which is essential to cell survival. The plasma membrane allows nutrients in and wastes out of the cell. The most important property of the plasma membrane is its ability to be selectively permeable. This means it can allow certain substances to pass through while keeping other substances out. Examine Figure 5 on page 187 in your text. Oxygen, water and glucose are some of the substances allowed to enter the cell, but waste is not.