BiologyCell Theory

Chapter 7

Cell- smallest unit that can carry on all the processes of life

2 types of organisms:

1. Unicellular organism- living thing that consists of only ONE cell

Ex: paramecium, bacteria

2. Multicellular organism- living thing that consists of MORE THAN one cell

Ex: humans, plants, animals

Knowledge of cells began with the invention of the lens in the 1600s and has increased today with the electron microscopes

Robert Hooke- 1st person to view cells under the microscope

observed thin slices of cork (plant)

saw little empty boxes - called cells

Hooke was the 1st to look!

Hooke’s microscope and the cells he saw

Anton von Leewenhoek- 1st person to

view living cells in 1675

In 1838, Mathias Schleiden stated that ALL PLANTS were made up of cells

In 1839, Theodor Schwann stated that ALL ANIMALS were made of cells

In 1855, Rudolph Virchow concluded that CELLS COME ONLY FROM EXISITNG CELLS

Cell theoryAll these observations were combined to form the cell theory:

1. All living things are composed of one or more cells.

2. Cells are an organism’s basic unit of structure and function.

3. Cells come only from existing cells.

Cellsnot all cells are the same, but they do have some similarities: all have a cell membraneall will have some DNA (genetic material)

all will perform the processes of life

there are some cells that have little structures that will perform certain functions for the cell

these structures are ORGANELLES

they’re like our organs in our bodies

there are 2 categories of cells:

1. Prokaryotic cellssimplest type of cellsno membrane bound organelles

no nucleushave cell membrane

The only organisms to have prokaryotic cells are

bacteria

2. Eukaryotic cellshave membrane bound organelleshave nucleususually larger, more complex

ALL other organisms are made up of eukaryotic cells

How do they compare?

Microscopescompound light microscope- uses 2 or more lenses to magnify objects

can magnify up to 1500 x

Electron microscopes

use a beam of electrons to magnify objects

developed in 1930-1940s

magnifies 50 000x and more!

Scanning Electron Microscope

3-D picture is produced

sweeps beams of e- over specimen

magnifies up to 60 000x

Transmission Electron Microscope

aims beams of e- through specimen

can magnify up to 100 000x

Scanning Tunneling Microscope

probe detects atoms at surface of specimen

can magnify objects up to 100 000 000x!