Download Lesson 1

Grade 10 Applied Science – Biology
Cell Theory
Cells are the basic units of life. They are the building blocks of all organisms, from bacteria to
animals.
In 1665, Robert Hooke used a very primitive microscope, to see cells in cork.
The Cell Theory was developed from the discoveries of three German scientists: Matthias
Schleiden, Theodor Schwann, and Rudolph Virchow. In 1838, Schleiden determined plants were
made of cells. In 1839, Schwann discovered all animals were composed of cells. In 1855,
Virchow revealed all cells come from existing cells.
The modern tenets of the Cell Theory
1. All known living things are made up of cells.
2. The cell is the structural and functional unit of all living things.
3. All cells come from pre-existing cells by division. (Spontaneous Generation does not
occur).
4. Cells contain hereditary information which is passed from cell to cell during cell
division.
5. All cells are basically the same in chemical composition.
6. All energy flow (metabolism and biochemistry) of life occurs within cells.
The three main parts of the Cell Theory
 All organisms are made up of one or more cells

The cell is the fundamental unit of structure and function in living things

All cells are essentially the same in chemical composition
Types of Cells
Cells are classified as either prokaryotic or eukaryotic.
Prokaryote Cells have no nucleus or organelles with membranes. Thus, the parts of a prokaryotic
cell are
 Cell wall
 Cell membrane
 Ribosome
 A single chromosome with nucleic acid
Bacteria and blue-green bacteria are prokaryotic cells.
Eukaryote Cells contain:
 Nucleus with multiple chromosomes
 Cell organelles including ribosome and mitochondria
 Cell membrane.
The cells of protozoa, algae, fungi, plants and animals are eukaryotic cells.


Grade 10 Applied Science – Biology
Pasteur's Experiment to Disprove Spontaneous Growth
Nutrient broths were heated and sterilized in a flask with a straight neck and a curved
neck.
As his control, Pasteur used flasks with straight necks that permitted bacteria to settle
into the broth. In these flasks, the broth was soon teaming with bacteria.

Pasteur's experimental flasks had long S-shaped necks. With such necks bacteria could
not enter, even though they were exposed to air. Therefore no bacteria grew.

When the S-shaped neck was removed bacteria began to grow in the sterile media.