Diversity Of Cells Ch3.1 7th

DIVERSITY OF CELLS Chapter 3 Section 1

Objectives 

State the parts of the cell theory

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Explain why cells are so small

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Describe the parts of the cell

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Describe how bacteria are different from archaea

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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

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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.

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Discovered when microscopes were invented in the mid 1600’s

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Robert Hooke – first person to describe cells (looked at cork cells 1st)

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Cell means “little room” in Latin

Anton van Leeuwenhoek 

A Dutch merchant, who in 1673 made his own microscope

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Looked at pond scum – saw small organisms he called animalcules (“little animals”) – today protists

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Looked at animal blood (oval vs. round cells)

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First person to see bacteria & studied yeasts as single-celled organisms

Cell Theory 

Cell: smallest unit, covered by a membrane, have DNA and cytoplasm

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Matthias Schleiden studied plants (1838)

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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

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Large cell: yolk of a chicken egg

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Small cell: individual blood cells

Surface area-to-volume ratio 

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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 

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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

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Organelles: carry out specific functions; most surrounded by membranes

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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

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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?

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Why did Hooke think that cells existed only in plants and fungi and not in animals?