DIVERSITY OF CELLS Chapter 3 Section 1
Objectives
State the parts of the cell theory
Explain why cells are so small
Describe the parts of the cell
Describe how bacteria are different from archaea
Explain the difference between prokaryotic and eukaryotic cells
Interesting background info…
Microtomy: once referred to specimen cutting; today refers to the art of preparing specimens
Whole-mount prep of cells – Preserved,
stained, dried (alcohol removes water), made transparent in clove or cedar oil Mounted in a drop of resin on a glass slide covered with glass only 0.005mm thick
Cells and the Cell Theory
The smallest unit that can perform all processes necessary for life.
Discovered when microscopes were invented in the mid 1600’s
Robert Hooke – first person to describe cells (looked at cork cells 1st)
Cell means “little room” in Latin
Anton van Leeuwenhoek
A Dutch merchant, who in 1673 made his own microscope
Looked at pond scum – saw small organisms he called animalcules (“little animals”) – today protists
Looked at animal blood (oval vs. round cells)
First person to see bacteria & studied yeasts as single-celled organisms
Cell Theory
Cell: smallest unit, covered by a membrane, have DNA and cytoplasm
Matthias Schleiden studied plants (1838)
Theodore Schwann studied animals (1839) – wrote first 2 parts of cell theory: All
organisms are made of one or more cells The cell is the basic unit of all living things
Cell Theory continued…
Rudolf Virchow (1858) added the 3rd part of the cell theory: All
cells come from existing cells
Cell Size
Most cells are too small to be seen with the naked eye
Large cell: yolk of a chicken egg
Small cell: individual blood cells
Surface area-to-volume ratio
Cells take in food and get rid of wastes through their outer surface (membrane) As wells get bigger, they take in more food and make more wastes As volume increases, surface area grows too If it gets too large, it can’t take in enough nutrients or pump enough wastes Cell’s surface area limits cell size
Formula:
Surface area-to-volume ratio = surface area / volume
Practice problems: pg. 62 Let’s
do the example together
Try
the practice problems (1-4) on your own…
Discuss
answers
Parts of a Cell
Cell membrane: protective layer (phospholipid); barrier; controls flow of materials; separates cell’s contents from its environment Cytoplasm: Inside fluid portion of cell & its contents
Organelles: carry out specific functions; most surrounded by membranes
Genetic material: DNA; some cells have a nucleus (an organelle in eukaryotic cells) that contains the DNA
Two Kinds of Cells
Cells with and without a nucleus: Prokaryotic
Cells: have no nucleus or membrane bound organelles Bacteria Archaea
Eukaryotic
Cells: have a nucleus
Prokaryotic Cells
Bacteria: small organisms that live almost everywhere No
nucleus DNA (long circular, twisted molecule) Ribosomes (made of protein) Strong exterior wall (membrane is just inside cell wall) Flagellum (helps the bacterium to move) Good and bad bacteria
Bacterial structure
http://www.ict-science-tosociety.org/Pathogenomics/images/bacteria_cell.jpg
Prokaryotic Cells
Archaea: similar to bacteria Both
have ribosomes, cell membranes, circular DNA, lack a nucleus and membrane bound organelles
But,
archael ribosomes are different than bacterial ribosomes – more like eukaryotic ribosomes
Different Live
cell walls
in places no other organisms can live
Archaea
3 types: Heat-loving
(extremophiles)
Salt-loving Methane-making
(a gas in swamps,
volcanic vents) Example:
Pyrodictium live at 105˚C (5˚C hotter than boiling water
http://www.love-isfreedom.com/gesundheit/infektion/biblothek_taxonomy/Pyrodictium.jpg
Eukaryotic Cells
Microscopic but still 10 times larger than bacterial cells Have a nucleus (houses the DNA) Membrane bound organelles Multi-cellular (“many cells”) organisms Examples:
plants, animals, green algae, mushrooms
Single-celled Examples:
(fungi)
amoebas (protists), yeasts
Eukaryotes
http://www.biologie.uni-hamburg.de/bonline/library/onlinebio/5_6.jpg
http://waynesword.palomar.edu/images/plan t3.gif
Quick Quiz
When Robert Hooke saw “juice” in some cells, what was he looking at?
Why did Hooke think that cells existed only in plants and fungi and not in animals?