cell theory

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Transcript cell theory

• All living things are made of cells, the
smallest unit that can carry on all the
processes of life
• In 1665, Robert Hooke observed the first
cells from thin slices of cork. He gave
them the name "cells" because they
reminded him of small rooms or cells that
monks lived in.
• In 1675, Anton van Leeuwenhoek was the
first person to observe living cells. He
looked at
protozoans from pond water.
• About 150 years later scientists organized
their observations into a cell theory:
- All living things are composed of one
or more cells.
- Cells are the basic units of structure
and function in an organism.
- Cells come only from existing cells.
Prokaryotic Cells (Bacteria)
• The average size is about 1 micrometer.
Bacteria have no nucleus and no
membrane-bound organelles. An
organelle is a cell component that
performs specific functions for the cell.
Cell Membrane • separates the cell from its environment.
It regulates what moves into and out of
the cell.
The Fluid Mosaic Model: the cell
membrane is made up of 2 layers of
phospholipids with proteins embedded
throughout. These lipids and proteins
constantly move laterally creating a fluid
• the entire contents of the cell, except the
• site where proteins are made.
• tangled ball of DNA; tells cell what
proteins to make.
It is not called a nucleus because the
DNA is not contained within a membrane.
• small rings of DNA (separate from the
Pili (pilus)
• appendages that allow the bacteria to
adhere to other surfaces.
• long extensions that aid in movement
Cell Wall
• outer rigid layer; maintains the shape of
the cell and adds protection.