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Transcript
Prokaryotes & Eukaryotes By Diana L. Duckworth Rustburg High School Campbell County Features in common • All cells are surrounded by a plasma membrane • Inside membrane is semifluid substance called cytosol (cytoplasm) • All cells contain chromosomes carrying genes in form of DNA • All cells contain ribosomes (site of protein manufacture) Prokaryotic Cells http://www.prof2000.pt/users/biologia/tipocelu.htm • DNA found in region called nucleoid • No membrane isolates DNA from cytosol • No specialized organelles in cytosol • May have cilia or flagella for locomotion • Cell wall – rigid structure outside membrane • May have a capsule around cell wall http://darwin.nox.ac.uk/gsc/gcat/mashup?query= Streptococcus http://www.kimicontrol.com/edu-e.html http://www.bact.wisc.edu/themicrobialworld/Structure.html Eukaryotic Cell • DNA combines with histones to form chromosomes • Inside a nuclear membrane (DNA isolated from cytoplasm) • Well defined nucleus • Numerous specialized organelles in cytoplasm • Many internal membranes • Much larger than prokaryotes http://www.physci.wsc.ma.edu/young/hgeol/geoinfo/timeline/eukaryotes/eukaryotes.html chloroplast Cell wall http://library.thinkquest.org/3564/gallery.html vacuole http://www.sinauer.com/cooper/4e/micrographs0102.html Plant Cell Animal Cell Why be small? • Cells must obtain nutrients & expel wastes across cell membranes • As size decreases, surface area increases. • Amount of surface area/volume increases. • Cell functions more efficiently. Cell or Plasma Membranes • Phospholipid Bilayer • Hydrophobic lipid tails orient away from water in cytoplasm & outside cell • Hydrophyllic heads contain phosphate groups • Lipid tails either saturated or unsaturated http://sun.menloschool.org/~cweaver/cells/c/cell_membrane/ Electron Micrograph of Cell Membranes 8 nm thick Cell membranes http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html Membrane Proteins http://library.thinkquest.org/C004535/cell_membranes.html • Ends of proteins are hydrophyllic • Center is hydrophobic • Integral proteins go through membrane • Peripheral proteins are only on surface • Proteins have many functions (later) Other Components of Membranes • Carbohydrate chains attached to proteins (glycoproteins) or lipids (glycolipids) – (blood types) http://sun.menloschool.org/~cweaver/cells/c/cell_membrane/ Membranes are fluid Phospholipids move 10 million times/second Some proteins move; others don’t • In animal cells cholesterol molecules are embedded in membrane – Keeps membrane fluid at low temps (homeostasis) Membranes are “sided” • Selective permeability – Allow some things in and not others • Vacuoles expell some waste & proteins to outside • Vacuole membrane must merge with cell membrane http://employees.csbsju.edu/hjakubowski/classes/ch331/cho/ergolgi.jpeg – Inside of vacuole is same as outside of cell