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Cell Theory and Structure
Discovery of the Cell• Scientists did not start using simple compound
microscopes until the mid 1600’s.• Robert Hooke used an early compound microscope
to look at slices of cork.
• Hooke named the ‘seemingly empty’ chambers ‘cells.’
• Around the same time, Anton von Leeuwenhoek was using a single-lens microscope to observe unicellular organisms in pond water for the first time.
http://www.smithlifescience.com/cork2.GIF
Cell Theory
•Additional observations of cells in other living things led scientists to 3 basic conclusions, known as the cell theory.
•Cell Theory states:▫All living things are composed of cells.▫Cells are the basic units of structure and
function in living things.▫New cells are produced from existing cells.
There are two categories of cells……
•Prokaryotes▫No nucleus▫Few organelles▫Small in size
▫Ex: Bacteria
EukaryotesEukaryotes– NucleusNucleus– Many Many
organellesorganelles– Large in sizeLarge in size– Ex: Humans, Ex: Humans,
plants, fungi, plants, fungi, etc.etc.
http://www.cod.edu/people/faculty/fancher/EukaryoticCell.jpg
http://www.cod.edu/people/faculty/fancher/ProkaryoticCell.jpg
Cell Structure
•All cells, both prokaryotes and eukaryotes, have DNA and a cell membrane.
•Cells also contain organelles – specialized structures within the cell that perform certain tasks.
•These organelles float around in the cell’s cytoplasm, which is mostly made of water.
Prokaryotes…….they’re simple.•Prokaryotes only have a
few basic structures:▫DNA▫Cell/plasma membrane▫Cell wall▫Ribosomes
▫Some use structures like pili, cilia, and flagellum to move in aquatic environments. http://scienceblogs.com/clock/2006/11/cell_structure.php
….but they come in many varieties.
http://images.google.com/imgres?imgurl=http://www.harlem-school.com/10TH/sci_pdf/graphics/prokaryotic_entities.gif&imgrefurl=http://www.harlem-school.com/10TH/sci_pdf/sci.html&h=396&w=284&sz=32&hl=en&start=12&tbnid=dQsSJBBu88uFiM:&tbnh=124&tbnw=89&prev=/images%3Fq%3Ddifferent%2Bshaped,%2Bprokaryotic%26gbv%3D2%26svnum%3D10%26hl%3Den%26safe%3Dactive
Eukaryotes are more complex.
•Eukaryotes can be multicellular or unicellular.
•Eukaryotes contain many organelles…….
Do you know your Organelles?
Cell (plasma) membrane
•Regulates what materials enter and leave the cell.
Nucleus
• Controls most cell processes and contains nearly all of the cell’s DNA
Ribosomes
• assemble proteins.▫ Some are free floating while others are attached to the
endoplasmic reticulum.
• There are two types:▫ Rough – chemically modifies proteins that are produced
by the ribosomes on its surface.▫ Smooth – contains specialized enzymes and makes lipid
components for the cell membrane.
Endoplasmic Reticulum (ER)
•Sorts, modifies, and/or packages proteins and other materials from the ER for storage or secretion from the cell.
Golgi apparatus
• Lysosomes contain enzymes that are specialized to digest lipids, carbs, proteins so their monomers can be reused
• Peroxisomess contain enzymes that are specialized to digest toxic substances
Lysosomes and peroxisomes
Cytoskeleton
•A network of protein filaments (microtubules and microfilaments) that help the cell move and maintain its shape
http://scienceblogs.com/clock/2006/11/cell_structure.php
•Provides the cell with usable chemical energy ▫It is the site of cellular respiration.
Mitochondria
How are they different?
http://staff.tuhsd.k12.az.us/gfoster/standard/BCELL1_files/image005.jpg
http://scienceblogs.com/clock/2006/11/cell_structure.php
Plant cells have special features…..•Plants contain:
▫Chloroplasts – create and store usable energy through the process of photosynthesis.
▫Cell wall – provides the cell with rigid structure.
▫1 Large vacuole – used for the storage of water and some other materials Animal cells usually have many small
vacuoles
Some organelles have their own DNA….•Only two organelles have their own DNA –
mitochondria and chloroplasts.•Endosymbiotic Theory – suggests that
mitochondria and chloroplasts are the decendents of ancient prokaryotes that developed symbiotic relationships with ancient cells.
http://micro.magnet.fsu.edu/cells/chloroplasts/images/chloroplastsfigure1.jpg http://en.citizendium.org/images/c/c7/MitochondriaSMALL2.jpg