cell theory chapter 7. cell - smallest unit that can carry on all the processes of life 2 types of...
TRANSCRIPT
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!