Post on 21-Jan-2022
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