Prokaryotic and Eukaryotic Cell Structure

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Prokaryotic and Eukaryotic Cell Structure

• And a Little Taxonomy too!

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Taxonomy

• The science of classification of living
  organisms.
• So we can identify and understand relationships
  between organisms.

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Phylogeny

• Method of grouping organisms based on their
  evolutionary history.
• Uses shared characteristics that reflect
  evolutionary history.
• What are some shared characteristics used?

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Linnaean System

• First developed by Carolus Linnaeus (1707-1778).
• Method of classifying things in a hierarchical
  structure from most general to most similar.
• Binomial System (2 names)
• Domain
• Kingdom (most general)
• Phylum or Division
• Class
• Order
• Family
• Genus
• Species

CR4. 2007. http//cr4.globalspec.com/blogentry/20
67/Happy-Birthday-Carolus-Linnaeus
Ex. Eschericia coli or E. coli
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Classification

• Domains constitute a level of classification
  above the kingdom.
• Domains are further subdivided into kingdoms etc.

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The 3 Domains

• 1. Archaea 2. Bacteria 3. Eukarya
• - animals
• - plants
• - algae
• - protozoa
• - fungi

Prokaryotes
Eukaryotes
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Kingdoms

• Based on similar morphology, geographic
  distribution, and if multicellular, the ability
  to interbreed.

Bacteria
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A phylogenetic tree based on rRNA data showing
Woeses three domain system. Retrieved from
http//en.wikipedia.org/wiki/Kingdom_28biology29
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Bergey System

• Another system for classifying Prokaryotes.
• Still use kingdom, division or phylum, class,
  order, family, genus, species.
• Classification based on similar morphological and
  biochemical characteristics.

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Eukaryotic and Prokaryotic Cells

• How are they different and
• how are they the same?

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What Is a Cell?

• It is the fundamental unit of all living matter.
• Has all characteristics of life.
• Can live independently of other cells.

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All Cells Have the Following

• Enzymes
• A protein that speeds up a chemical reaction.
• DNA deoxyribonucleic acid
• A large molecule that stores genetic information.
• RNA ribonucleic acid
• A large molecule involved in protein synthesis.
• ATP adenosine triphosphate
• The main energy currency of a cell.
• Amino Acids
• Proteins are composed of basically the same 20
  amino acids.

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What cellular structures are found in all living
things?
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Eukaryotic Cell Structure

• Possess membrane-bound organelles.
• 10-30µm in diameter.
• Eukaryote true nucleus
• Their DNA is enclosed by a double membrane.

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Eukaryotic Cell Structure

• Cell Membrane
• Phospholipid (fatty chain with a phosphate)
  bi-layer with different types of proteins
  interspersed.
• Separates inside of cell from external
  environment.
• It has selective permeability.
• Only certain things can get in and out.
• Other organelle membranes are similar in
  structure.

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Cell Membrane
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Eukaryotic Cell Structure

• Nucleus
• Controls the functions of the cell (the control
  center).
• Nuclear membrane surrounds nucleus.
• Nucleoplasm gelatinous matrix.
• Chromosomes linear DNA molecules and proteins.
• Gene specific DNA segment on the chromosome
  that contains the information for making a gene
  product, usually a protein.
• Nucleolus where rRNA is made and is used to
  make a structure called ribosomes.

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Eukaryotic Cell Structure

• Cytoplasm
• A semi-fluid, gelatinous, nutrient matrix.
• Contains storage granules and cell organelles.
• Most of cells metabolism occurs.
• Often called the cytosol.

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Eukaryotic Cell Structure

• Endoplasmic Reticulum (ER)
• An irregular maze of spaces enclosed by a
  membrane.
• Assembly Line
• Rough ER
• Contains ribosomes
• Involved in making proteins
• Smooth ER
• Does not contain ribosomes
• Involved in lipid metabolism (fat storage)

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Eukaryotic Cell Structure

• Ribosomes
• Are important in protein synthesis.
• Are found in the Rough ER.

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Eukaryotic Cell Structure
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Eukaryotic Cell Structure

• Golgi Complex
• packaging plant.
• Stacks of flattened, membranous sacs.
• Completes and packages newly formed proteins and
  lipids.
• Packages them so that they are ready for storage
  within the cell or outside of the cell.

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Eukaryotic Cell Structure

• Lysosomes
• garbage disposal system
• 1 µm diameter
• Contain lysozyme and other enzymes that break
  down foreign material.
• Particles may enter cell by phagocytosis.
• Also involved in programmed cell death called
  autolysis or apoptosis.
• Peroxisomes
• Membrane-bound vesicles that generate and break
  down hydrogen peroxide (a dangerous and highly
  reactive chemical).
• Used to break down lipids (fats) and destroy
  toxic molecules.

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Eukaryotic Cell Structure

• Mitochondria
• the power plant of the cell
• 0.5 1 µm in diameter, 7 µm in length
• Where ATP (adenosine triphosphate) is formed.
• ATP is the energy currency of the cell.
• ATP is formed during a reaction called cellular
  respiration.
• ATP is formed from our food sources.

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Eukaryotic Cell Structure
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Eukaryotic Cell Structure

• Plastids
• Site of photosynthesis.
• Contain photosynthetic pigments.
• Photosynthesis converting light energy into a
  source of chemical energy for organism.
• Chloroplasts type of plastid that contains
  chlorophyll.
• Chlorophyll a green photosynthetic pigment.

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Eukaryotic Cell Structure- Plant Cell
micro.magnet.fsu.edu/cells/plants/plantmodel.html
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Eukaryotic Cell Structure

• Cell Wall
• External structure that provides rigidity, shape,
  and protection.
• May be composed of cellulose, pectin, lignin,
  chitin, and some mineral salts.
• Usually simpler than prokaryotic cells.

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Eukaryotic Cell Structure
Plant Cells
Cells stained green (DNA) and red
(keratin) www.newworldencyclopedia.org/entry/Cell_
(biology
Illustration by Robert Hooke (c.1665) askabiologis
t.asu.edu/.../rhooke.html
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Cell Walls
Cell Walls

• Present
• Plants
• Algae (protists)
• Fungi
• Most Bacteria

• Absent
• Animals
• Protozoa (protists)
• Mycoplasma species (type of bacteria)

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Eukaryotic Cell Structure

• Flagella
• An organelle of movement.
• Long, thin structure that moves like a whip to
  propel organism through liquid environment.
• Can be found in some species of protozoa,
  spermatozoa, and algae.
• Cilia
• Organelle of locomotion.
• Usually short, hair-like structures that beat in
  coordinated, rhythmic movement.
• Can be found in some species of protozoa and
  types of cells that line respiratory tract.

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Eukaryotic Cell Structure
Paramecium sp. Protozoa. Notice the
cilia. microbewiki.kenyon.edu/index.php/Paramecium

Euglena sp. Protozoa. Notice the
flagella. www.biologie.uni-erlangen.de/.../fotonm3
_eng.htm
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Prokaryotic Cell Structure

• More simple than eukaryotic cells.
• Can perform all functions necessary for life.
• Prokaryotes comprise all bacteria and archaeans.
• Do NOT contain membrane-bound organelles.
• Typical E. coli cell is about 1 µm wide and 2-3
  µm long.

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Prokaryotic Cell Structure

• Bacterial Cell Wall
• Provides rigidity, strength, and protection.
• More complex than eukaryote cell walls.
• Composed of peptidoglycan (polymer of sugars and
  amino acids)
• Gram-positive bacteria
• Thick layer of peptidoglycan with some other
  molecules.
• Gram-negative bacteria
• Thinner layer of peptidoglycan with an outer
  membrane composed of lipid macromolecules.
• Genus Mycoplasma do not have cell walls.
• Archaens have cell walls but not composed of
  peptidoglycan.

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Prokaryotic Cell Structure

• Cell Membrane
• Similar to eukaryotic cells.
• Contains proteins and phospholipids.
• Selectively permeable.
• It is very flexible and thin.

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Prokaryotic Cell Structure

• Glycocalyx
• Thick, slimy, gelatinous material produced by the
  cell membrane and secreted outside the cell wall.
• Some bacteria have it.
• 2 types of glycocalyx
• 1. Slime Layer
• Is not highly organized or firmly attached to
  cell wall.
• Allows bacteria to glide or slide along surfaces.
• 2. Capsule
• Highly organized and firmly attached to cell
  wall.
• Chemical composition allows scientists to
  determine different types of bacteria.
• Prevent bacteria from being phagocytized by
  phagocytic white blood cells.
• Can attach bacteria to a wide array of surfaces.

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Prokaryotic Cell Structure
diverge.hunter.cuny.edu/weigang/Lecture-syll.
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Prokaryotic Cell Structure

• Prokaryotic Chromosome
• Single, long, supercoiled, circular DNA molecule.
• Embedded in cytoplasm.
• Found in nuclear region of cell.
• Does not have a nuclear membrane.
• Contains all the information for carrying out
  life processes.
• Plasmids may also be found in prokaryotic cells.

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Prokaryotic Cell Structure

• Plasmid
• Small, circular molecule of double-stranded DNA.
• Not part of the chromosome.
• Called extrachromosomal DNA.
• Found in the cytoplasm.
• May contain 10-100s genes.
• Number varies per cell.

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Prokaryotic Cell Structure

• Cytoplasm
• Semiliquid interior of cells.
• Consists of water, enzymes, dissolved oxygen (in
  some bacteria), waste products, nutrients,
  proteins, carbohydrates, and lipids.
• Everything necessary for its metabolic functions.

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Prokaryotic Cell Structure

• Cytoplasmic Particles
• Ribosomes are found in the cytoplasm.
• They are important in protein synthesis.
• Some substances are stored in cytoplasmic
  granules.
• Such as starch, lipids, sulfur, or iron.
• The type of substance stored depends on the
  species of organism.

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Prokaryotic Cell Structure
diverge.hunter.cuny.edu/weigang/Lecture-syll.
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Prokaryotic Cell Structure

• Flagella
• A mechanism for movement for some bacteria.
• Bacteria can be classified and identified by the
  arrangement of their flagella.
• Nonflagellated bacteria are usually considered to
  be nonmotile.
• Although there are exceptions.

Pseudomonas fluorescens aerobic soil
bacteria. www.scienceclarified.com/As-Bi/Bacteria.
html
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Prokaryotic Cell Structure

• Pili (Fimbriae)
• Not associated with motility.
• Thin, rigid, hair-like structure.
• Arise in cytoplasm and extend through the plasma
  membrane, cell wall, and capsule (if present).
• 2 types of pili
• 1. Adhesins - allows bacteria to adhere to
  surfaces.
• 2. Sex pilus
• Allows for the transfer of genetic material
  through a process called conjugation.
• One bacteria attaches its sex pilus to another
  cell and transfers its genetic material to the
  other cell usually in the form of a plasmid.

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Prokaryotic Cell Structure
Adhesin bacterial cell with pili (fimbriae)
ultr23.vub.ac.be/.../fimbrialadhesion.html
Bacterial conjugation with sex pilus.
www.cbs.dtu.dk/.../roanoke/genetics980309.html
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Prokaryotic Cell Structure

• Spores (Endospores)
• Bacterial spores called endospores.
• Usually found in 2 genera Bacillus and
  Clostridium.
• Form through the process sporulation.
• A copy of the chromosome and some cytoplasm is
  enclosed in a thick protein coat.
• This occurs when moisture and nutrients are low.
• Endospores are resistant to heat, cold, drying,
  and most chemicals.
• If adequate conditions are present, the endospore
  can become an active bacteria.

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Endospore

• Clostridium difficil forming an endospore.
• Associated with antibiotic related diarrhea
  caused by toxins produced
• Red structure is endospore forming.

www.chem.wayne.edu/feiggroup/research.htm
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Prokaryotic Cell Reproduction

• Binary Fission
• One parent cell splits to become 2 daughter
  cells.
• This process produces a clone of the parent cell.
• During this process, its chromosome is replicated
  in a process called DNA replication.
• Generation time
• The time it takes one parent cell to become 2
  identical daughter cells.

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Binary Fission
www.uic.edu/.../bios100/lecturesf04am/lect06.htm
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The End