FOCUS 1- Organisms are made of cells that have similar structural characteristics

Key Terms:

* Cell: The basic structural and functional unit of all organisms

* Theory: A supposition or a system of ideas intended to explain something, esp. one based on general principles independent of the thing to be explained

* Electron Microscope: A microscope that is similar in purpose to a light microscope but achieves much greater resolving power by using a parallel beam of electrons to illuminate the object instead of a beam of light

* Light Microscope: Microscope consisting of an optical instrument that magnifies the image of an object

* Organelle: Any of a number of organised or specialized structures within a living cell

The cell theory has three main points:

* Cells are the smallest units of life

* All living things are made up of cells

* All cells come from pre-existing cells

The main points in the historical development of the cell theory are:

* 1485 - Leonardo da Vinci used glass lens to study small objects * 1600 - The first compound microscope was made by Hans and Zacharias Janssen * 1665 - ROBERT HOOKE observed cork cells using a compound microscope and described ‘little boxes or cells distinct from one another’ * 1676 - Anton von Leeuwenhoek described unicellular organisms in pondwater * 1831 - ROBERT BROWN observed the nucleus in plant and animal cells * 1839 - Schleiden and Schwann formulated the cell theory that all living things are made up of cells. Schwann was the first scientist to see yeast cells producing new cells * 1858 - Virchow stated: "where a cell exists, there must have been a pre-existing cell, just as the animal only arises from an animals and the plant only from a plant." * 1880 - Walter Flemming described cell division (mitosis) from observations on living and stained cells

Describe evidence to support the cell theory:

* Robert Hooke’s observation of cork cells and…

* Leeuwenhoek’s observation of many types of unicellular cells proved that living things were made up of cells

* Walter Flemming’s observation of cell division – mitosis- proved that cells come from pre-existing cells.

Discuss the significance of technological advances to developments in the cell theory:

The cell theory would not develop without technological advances. The main advance in technology would be the development in the design of the microscope as the microscope enabled us to see cells in greater detail than ever before. Another development is the preparation of specimen, such as the staining of cells, which enabled the division of the nucleus to be observed. These are examples of how technological advances go hand in hand with the development of the cell theory.

Identify cell organelles seen with current light and electron microscopes:

A light microscope uses light and focuses with lenses to see small objects. An electron microscope uses electron beams and focuses them with electromagnets to see small objects

Organelles seen under a LIGHT MICROSCOPE:

- Nucleus
- Cell membrane
- Nuclear membrane
- Cytoplasm
- Vacuoles
- Cell wall
- Chloroplasts

Organelles seen under an ELECTRON MICROSCOPE:
- Nucleolus
- Mitochondria
- Ribosomes
- Endoplasmic reticulum
- Lysosomes
- Centrioles
- Cytoskeleton
- Golgi body

Identify the relationship between the structure of cell organelles and their function:

Function
Structure
Nucleus
The control centre for the cell; stores genetic material (DNA) and controls the cell’s structure and functions (all activities).
Contains chromosomes and nucleolus. Has large pores in nuclear membrane to allow large molecules, such as genetic information and proteins to move in and out
Nucleolus
Organises Ribosomes and other products with RNA.
A mass of RNA within the nucleus
Mitochondria
Energy production and controls