History of Cell Theory &

Cellular Structures

The Discovery of Cells

• Anton van Leeuwenhoek• Used a simple microscope• He was the first person to

use a microscope to study

nature.• He was the first to see tiny living organisms in a drop of

water.

The Discovery of Cells

• Wanted to know why corks float.

• Looked at cork

(plant) cells.

• Looked like monk’s

cells.

• Term “cell” was coined in 1665 by Robert Hooke when he looked at a slice of dried cork.

The Discovery of Cells

• Mid 1800’s Frenchman named Dujardin found what we now call protoplasm. It is the living material within a cell.

• About the same time an English scientist

named Robert Brown

observed the interior of the cell.

The Discovery of Cells

• Using a very simple microscope, he observed an opaque spot

in a plant which

he named the nucleus.

The Cell Theory

• Contributors to Cell Theory

• Matthias Schleiden-All plants are

are made of cells.

Theodor Schwann-All animals

are made of cells.

The Cell Theory

• Rudolph Virchow

• Proposed that all cell come from existing cells.

• Completing the cell

theory.

Cell Theory

1. All living things are comprised of cells.

2. Cells are the smallest “living” unit in an organisms.

3. Cells come from previously existing cells.

Cell Diversity

• Lots of shapes and sizes

Two Categories of Cells

• Biologists divide cells into two categories:

eukaryotes and prokaryotes.

• The cells of eukaryotes have a nucleus, but the cells of prokaryotes do not.

• Bacteria are prokaryotes.

Prokaryotes

Eukaryotes

Cell Organization

The cell includes two basic parts:

1. Cell Membrane-a thin, flexible barrier around the cell. Plants have also have a cell wall.

2. Cytoplasm-fluid material inside the cell membrane. Many cell organelles (cell organs) found in cytoplasm.

Cell Membrane

• The cell membrane forms the outside boundary that separates the cell from its environment.

• Main function is to control what substances come into and out of a cell.

• Acts like a window screen.

Cell Membrane

Nucleus

• Control center of cell

• Acts like a

“Brain”

• Contains

the genetic

material.

Organelles in Cytoplasm

Endoplasmic reticulum (ER)

A network of membrane-bound tunnels that carry proteins and other materials.

Ribosomes

• Particles attached to ER are ribosomes.

• Ribosomes function as factories to produce proteins.

Golgi Apparatus

• Flattened sacs and tubes

• Involved in packaging and secretion of proteins

• Acts like

the cells

“mailroom”

Mitochondria

• Bean shaped

• Use energy from food to make high-energy

that the cell

can use for

growth,

movement and

development.

Other organelles

• Chloroplasts-Found in plant cells

Capture energy from sunlight to produce

food

• Vacuoles-storage area for the cell

• Lysosome-small round structures that contain chemicals that break down food particles and old cells, “Clean up crew”