NOTES: 7.1 - Introduction to

the Cell

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

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

3. Cells are produced only from existing cells.

MICROSCOPES

1. Light Microscope

2. Electron Microscope (1940’s)

• Scanning Electron Microscope

• Transmission Electron Microscope

Light Microscope

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

• magnification about 1000x - 1500x

Electron Microscope (1940’s)

• uses electron beams

which have shorter

wavelengths of light (so

you can see smaller

objects…more detail)

• magnification up to

500,000x

Electron Microscope1. Scanning Electron Microscope

– electron beam scans the surface of a specimen

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

2. Transmission Electron Microscope – electrons transmitted through

specimen– used to study internal cell

structure

Disadvantages to EM…

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

• very expensive

zooxanthellae cells cultured from coral

Aiptasia pulchella in a Scanning Electron

Microscope

ALL CELLS:

• have a cell membrane

• have cytoplasm

• have ribosomes

• can reproduce &

contain genetic

material

CELLS CAN BE CLASSIFIED AS:

1. PROKARYOTES

2. EUKARYOTES

See… no nucleus!!!See… no nucleus!!!

See… a nucleus!!!See… a nucleus!!!

PROKARYOTES EUKARYOTES

• oldest cells (3.5 billion years)

• “newer” cells (1.5 billion years)

PROKARYOTES EUKARYOTES

• oldest cells (3.5 billion years)

• single celled

• “newer” cells (1.5 billion years)

• single or multicellular

PROKARYOTES EUKARYOTES

• oldest cells (3.5 billion years)

• single celled

• lack nucleus & membrane-bound organelles

• “newer” cells (1.5 billion years)

• single or multicellular

• have a “true” nucleus & membrane-bound organelles

PROKARYOTES EUKARYOTES

• oldest cells (3.5 billion years)

• single celled

• lack nucleus & membrane-bound organelles

• genetic material in a single, circular molecule

• “newer” cells (1.5 billion years)

• single or multicellular

• have a “true” nucleus & membrane-bound organelles

• genetic material organized and in nucleus

PROKARYOTES EUKARYOTES

• oldest cells (3.5 billion years)

• single celled

• lack nucleus & membrane-bound organelles

• genetic material in a single, circular molecule

• small (1-2 µm)

• “newer” cells (1.5 billion years)

• single or multicellular

• have a “true” nucleus & membrane-bound organelles

• genetic material organized and in nucleus

• larger (2-1000 µm)

PROKARYOTES EUKARYOTES

• oldest cells (3.5 billion years)

• single celled

• lack nucleus & membrane-bound organelles

• genetic material in a single, circular molecule

• small (1-2 µm)

• Kingdoms archaebacteria & eubacteria

• “newer” cells (1.5 billion years)

• single or multicellular

• have a “true” nucleus & membrane-bound organelles

• genetic material organized and in nucleus

• larger (2-1000 µm)

• Kingdoms Protista, Fungi, Plantae, Animalia

NUCLEUS

• membrane-bound organelle in eukaryotic cells;

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

envelope– contains all of the

information for cell to function