Post on 01-Apr-2015
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Cells: Prokaryotes v. Eukaryotes (extracts of 7-1 & ch19)
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7-1 Life Is Cellular
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The Discovery of the Cell
In 1665, Robert Hooke used an early compound light microscope to look at a thin slice of cork, a plant material.
Early Microscopes
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7-1 Life Is Cellular
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The Discovery of the Cell
At the same time, Anton van Leeuwenhoek used a microscope to observe pond water and other things.
Early Microscopes
Daphnia – water insectDaphnia – water insect
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7-1 Life Is Cellular
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The Discovery of the Cell
In 1838, Matthias Schleiden – all plants were made of cells.
In 1839, Theodor Schwann – all animals were made of cells.
In 1855, Rudolph Virchow – new cells were created only from division of existing cells.
These discoveries led to the cell theory.
What is the cell theory?
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7-1 Life Is Cellular
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The Discovery of the Cell
Scientific Theory: A well tested explanation that unifies a broad range of observations.
•Scientific Theory used to make accurate predictions about new observations and situations.
•Scientific Theory can be revised according to new evidence
Cell Theory is a SCIENTIFIC THEORY!
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7-1 Life Is Cellular
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The Discovery of the Cell
• All living things are composed of one or more cells.
• Cells are the basic units of structure and function in living things.
» Use genetic code (DNA)» Over generations mutations accumulate and
lead to changes over time » Get energy and materials from environment to
run cellular metabolism» Respond to the external environment» Maintain homeostasis (stable internal
environment)
• New cells are produced from existing cells.
» Grow and develop
cell theory
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7-1 Life Is Cellular
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Exploring the Cell
Light microscope V. Electron microscope
Electron Microscope
Up to 100,000X
Preserved cells only
Scanning EM (3D image)
Transmission EM (2D cross section)
Light micrograph (LM)
Up to 1000X
Live or preserved cells
TEM
SEM
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7-1 Life Is Cellular
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Copyright Pearson Prentice HallFigure 4.4
DNA kept separate from the cell’s cytoplasm by the nuclear membrane
First cells (prokaryotic) 3.5 billion years ago
Eubacteria: common bacteria UC
First Eukaryotes(Has nucleus)
Scientist’s study of different organisms’ cell structure and DNA lead them to group organisms into 3 different domains
Archae-bacteria: Oldest bacteria typeUC
Protists Plants Fungi AnimalsUC&MC MC UC&MC MCUC&MC MC UC&MC MC
UC = unicellularMC= multicellular
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7-1 Life Is Cellular
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Prokaryotes and Eukaryotes
Prokaryotes and Eukaryotes
Prokaryote focus:
The smallest, simplest life forms are prokaryotes—unicellular organisms that lack a nucleus.
Biologists divided them into two different domains: the Eubacteria and the Archaebacteria.
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19–1 Bacteria
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Classifying Prokaryotes
Archaebacteria- Ancient bacteria
Achaebacteria’s DNA is more similar to eukaryotes than eubacteria!.
They live in extreme environments (why also known as extremeophiles)
●Methanogens live in oxygen-free environments, such as thick mud and animal digestive tracts.
●Other archaebacteria live in salty environments
● or in hot springs where water temperatures approach the boiling point.
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19–1 Bacteria
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Classifying Prokaryotes
Thermophiles of YellowstoneProduce Beautiful colors•This type of Extremophile requires temperatures above 45oC (113oF) to survive. •Wow: for most organisms, proteins and nucleic acids would denature at these hot temperatures. •Thermophiles source of enzymes used in DNA biotechnology
Grand Prismatic Spring Yellowstone.
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19–1 Bacteria
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Classifying Prokaryotes
Eubacteria include organisms that live in a variety of environments, including:
●in fresh and salt water
● on land
●in the human body
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Structures of Prokaryotic Cells
Nucleoid region – area where DNA is coiled in the cytoplasm. DNA is in direct contact with the rest of the cell
Plasmid – smaller circular DNA molecules – stores genes easily shared with other bacteria
Ribosomes – where proteins are made
cell membrane – encloses the cytoplasm of the prokaryotic cell, regulates what chemicals enter and leave the cell.
DNA PiliDNA Pili
PlasmidPlasmid
RibosomeRibosome
FlagellaFlagella
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Structures of the Prokaryotic Cell
Cell wall – rigid, composed of lipids, carbohydrates and protein. Protects the cell and maintains its shape
Pili – short surface projections found in some prokaryotes. Helps attach bacteria to surfaces
Flagella – long whiplike extensions found in some prokaryotes. Propel cell through liquid environments
Not all bacteria the a same shape!
•Bacilli (rod)
•Cocci (round)
•Spirilla (spiral)
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19–1 Bacteria
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Importance of Bacteria
Bacteria are vital to the living world.
Autotrophs: Some are producers that capture energy by photosynthesis.
Heterotrophs: using living organisms as food source.
●decomposers
●Nitrogen fixing bacteria
●Pathogens: cause disease
• Some bacteria damage the cells and tissues directly by breaking down the cells for food.
• Others By produce toxins that makes you sick
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Bacterial Disease in Humans
Bacterial Disease
Growth of pathogenic bacteria disrupts the body’s equilibrium by interfering with its normal activities and producing disease.
Antibiotics
Chemicals that kill bacteria w/o harming your cells
–Ex: Penicillin disrupts bacterial cell wall production
–Does not work on Viral infections
19–3 Diseases Caused by Bacteria and Viruses
Bacterial Diseases
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19–1 Bacteria
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Importance of Bacteria
Still other bacteria have human uses.
●foods
●Genetically engineered bacteria used to produce medicine
●production of some vitamins especially vitamins K in human intestines
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7-1 Life Is Cellular
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Prokaryotes and Eukaryotes
Compare & Contrast: What are the characteristics of prokaryotes and eukaryotes?
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7-1 Life Is Cellular
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Prokaryotes and Eukaryotes
Prokaryotes
Prokaryotic cells have genetic material that is not contained in a nucleus.
–do not have membrane-bound organelles.
–cells are generally smaller and simpler than eukaryotic cells.
–Bacteria (both archaebacteria and eubacteria) are prokaryotes.
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7-1 Life Is Cellular
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Prokaryotes and Eukaryotes
Prokaryotes and Eukaryotes
All cells have DNA to store hereditary information but where is it in the cells?
Eukaryotes have a nucleus – DNA surrounded by a a nuclear envelope membrane separating DNA from the rest of the cell
Eukaryotes have membrane bound organelles – like mitochondria and Endoplasmic Reticulum
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7-1 Life Is Cellular
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Prokaryotes and Eukaryotes
Eukaryotes
●Cells highly specialized
●In multicellular species groups of cells can form tissues
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7-1 Life Is Cellular
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Prokaryotes and Eukaryotes
Eukaryotic cells: Build the structures of Plants, animals, fungi, and protists.
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7-1 Life Is Cellular
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Prokaryotes and Eukaryotes
Compare and contrast Pro Both Eu