End Show Slide 1 of 31 Copyright Pearson Prentice Hall Cells: Prokaryotes v. Eukaryotes (extracts of 7-1 & ch19)

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Copyright Pearson Prentice Hall

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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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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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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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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• 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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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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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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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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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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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

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

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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Compare & Contrast: What are the characteristics of prokaryotes and eukaryotes?

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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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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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Eukaryotes

●Cells highly specialized

●In multicellular species groups of cells can form tissues

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Eukaryotic cells: Build the structures of Plants, animals, fungi, and protists.

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Compare and contrast Pro Both Eu

Documents

End Show Slide 1 of 31 Copyright Pearson Prentice Hall Cells: Prokaryotes v. Eukaryotes (extracts of 7-1 & ch19)