NOTESNOTES: 7.1 : 7.1 --

Introduction to the Introduction to the

CellCell

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

2.2. In organisms, cells are the basic In organisms, cells are the basic 2.2. In organisms, cells are the basic In organisms, cells are the basic unit of structure & functionunit of structure & function

3.3. Cells are produced only from Cells are produced only from existing cells.existing cells.

MICROSCOPESMICROSCOPES

1.1. Light MicroscopeLight Microscope

2.2. Electron Microscope (1940’s)Electron Microscope (1940’s)Electron Microscope (1940’s)Electron Microscope (1940’s)

•• Scanning Electron MicroscopeScanning Electron Microscope

•• Transmission Electron MicroscopeTransmission Electron Microscope

Light MicroscopeLight Microscope

works by passing visible light works by passing visible light through a thin section of through a thin section of specimen and then through specimen and then through specimen and then through specimen and then through glass lensesglass lenses

magnification about 1000xmagnification about 1000x --1500x 1500x

Electron Microscope Electron Microscope (1940’s)(1940’s)

uses electron beams which uses electron beams which

have shorter wavelengths have shorter wavelengths

of light (so you can see of light (so you can see

smaller objects…more smaller objects…more

detail)detail)

magnification up to magnification up to

500,000x500,000x

Electron MicroscopeElectron Microscope1.1. Scanning Electron MicroscopeScanning Electron Microscope

–– electron beam scans the surface of electron beam scans the surface of a specimena specimen

–– useful for studying the surface of useful for studying the surface of specimen in 3specimen in 3--DD

2.2. Transmission Electron MicroscopeTransmission Electron Microscope2.2. Transmission Electron MicroscopeTransmission Electron Microscope

–– electrons transmitted through electrons transmitted through specimenspecimen

–– used to study internal cell used to study internal cell structurestructure

Disadvantages to EM…Disadvantages to EM…

can only view dead cellscan only view dead cells (preparation (preparation steps kill living cells)steps kill living cells)

very expensivevery expensivevery expensivevery expensive

zooxanthellae cells

cultured from coral

Aiptasia pulchella in a

Scanning Electron

Microscope

ALL CELLS:ALL CELLS:

have a cell membranehave a cell membrane

have cytoplasmhave cytoplasm

have ribosomeshave ribosomeshave ribosomeshave ribosomes

can reproduce & contain can reproduce & contain

genetic materialgenetic material

CELLS CAN BE CLASSIFIED AS:CELLS CAN BE CLASSIFIED AS:

1. 1. 1. 1. 1. 1. 1. 1. PROKARYOTESPROKARYOTESPROKARYOTESPROKARYOTESPROKARYOTESPROKARYOTESPROKARYOTESPROKARYOTES

See… no nucleus!!!See… no nucleus!!!

2. 2. 2. 2. 2. 2. 2. 2. EUKARYOTESEUKARYOTESEUKARYOTESEUKARYOTESEUKARYOTESEUKARYOTESEUKARYOTESEUKARYOTES

See… a nucleus!!!See… a nucleus!!!

PROKARYOTES EUKARYOTES

• oldest cells (3.5 billion years)

• “newer” cells (1.5 billion years)

PROKARYOTES EUKARYOTES

single celled single or multicellular

PROKARYOTES EUKARYOTES

lack nucleus & membrane-bound organelles

have a “true” nucleus & membrane-bound organelles

PROKARYOTES EUKARYOTES

• genetic material in a single, circular molecule

genetic material organized and in nucleus

PROKARYOTES EUKARYOTES

• small (1-2 µm) larger (2-1000 µm)

•It would take 1,000,000 of them to fill 1 mm on a ruler

PROKARYOTES EUKARYOTES

Kingdom EubacteriaKingdom Archaebacteria(bacteria)

Kingdoms Protista, Fungi, Plantae, Animalia

NUCLEUSNUCLEUS

• membrane• membrane--bound organelle bound organelle in eukaryotic cells; in eukaryotic cells;

• • contains the cell’s DNAcontains the cell’s DNA• • contains the cell’s DNAcontains the cell’s DNA–– enclosed by a nuclear enclosed by a nuclear envelopeenvelope

–– contains all of the contains all of the information for cell to information for cell to functionfunction