BIO 205 Chapter 4 Powerpoint

8/14/2019 BIO 205 Chapter 4 Powerpoint

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BIO 205

Chapter 4


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Chlamydiae are extremely small, mostly pathogenic bacteria

Cyanobacteria carry out photosynthesis using chlorophyll,responsible for the appearance of oxygen in Earths earlyatmosphere

Actinobacteria include Streptomyces, the genus that produces theantibiotic streptomycin

Firmucutes consist of many gram-positive species, such asBacillus, Clostridium, Staphylococcus, and Streptococcus

Proteobacteria contain the largest and most diverse group ofspecies, including E. coliand many human pathogens

The majority of the 18 phyla ofBacteria play a positive role innature

The Domain Bacteria Contains Some of the Best Studied Prokaryotes


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Thermoacidophiles (grow athigh temperature with low

pH

Extreme halophiles (saltlovers)

Methanogens (live inanoxic environments)

Euryarchaeota contain:

The DomainArchaea ContainsMany Extremophiles

Crenarchaeota tend to grow inhot acidic environments suchas hot springs and volcanic

vents


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The Shapes and Arrangements of Prokaryotic Cells

Three Main Shapes:

Rod

Sphere

Spiral


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The Shapes and Arrangements of Prokaryotic Cells


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Streptococcus Chain


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Many cocci and some bacilli appear in groups or chains

A spherical bacterial cell is a coccus


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Spiral shaped bacteria can appear as vibrios (comma-shaped), spirilla (helical), or spirochete


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Prokaryotic Cell

Structure


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Pili

Pili help:

Pili Are Protein Fibers Extending from the Surfaceof Many Prokaryotes

Form biofilms andmicrocolonies.Some bacterialspecies have

conjugation pili,used to transfergenetic materialbetween cells

Attach cells to surfaces


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Prokaryoticflagella contain ahelical filament,a hook, and a

basal body

Flagella can be used for cell motility

Prokaryotic Flagella Are Long Appendages

Extending from the Cell Surface

Flagella


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Flagella Continued

Bacteria exhibit chemotaxis, moving up the concentrationgradient of a chemical attractant

Prokaryotic Flagella Are Long Appendages Extending fromthe Cell Surface

Some prokaryotes move without flagella by gliding across a

solid surface


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It protects cells from theenvironment, and allows them

to attach to surfaces

A thin diffuse layer ofpolysaccharides is a slime layer

A thick glycocalyx covalentlybound to the cell is a capsule

The glycocalyx is an adheringlayer of polysaccharides (andsometimes small proteins)

The Glycocalyx Is an Outer LayerExternal to the Cell Wall

Glycocalyx


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CapsuleCapsule in Acinetobacter species by negative staining


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Cell Envelope

The cell wall protectsthe cell from injury, andmaintains cell shapeand water balance

Cell Membrane

Cell Wall

The cell envelope iscomposed of two

parts:


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Prokaryotic Cell Wall

The outer membrane contains proteins called porinsthat selectively allow small molecules into the

periplasmic space

The gram-negative cell wall has an outer membrane,separated from the cell membrane by the periplasmic

space

Gram-negative bacteria have a two-dimensional

peptidoglycan layer and no teichoic acid

Gram-positive bacteria have thick peptidoglycan cellwalls containing teichoic acid

Cell walls in prokaryotes contain peptidoglycan


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The S-layer is the most common archaeal cell wall,consisting of protein or glycoprotein in a crystal lattice

Others have polysaccharides, proteins, or both

No archaea have peptidoglycan in the cell wall, but somehave pseudopeptidoglycan

The Archaeal Cell Wall Also Provides Mechanical Strength

Archaeal Cell Wall

P k ti C ll M b


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Prokaryotic Cell Membrane

Hydrophobic fatty acid chains in the phospholipids form a

permeability barrier

The phospholipid molecules are arranged in a bilayer

The cell membrane is a fluid layer of phospholipid and

protein (the fluid mosaic model)

The Cell Membrane Represents the Interface between theCell Environment and the Cell Cytoplasm


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molecule transport

sensation of stimuli

DNA replication

energy metabolism

cell wall synthesis

Membrane proteins perform or aid in many functions,such as:

Antimicrobial substances may disrupt or dissolve thebilayer

The Cell Membrane Represents the Interface between theCell Environment and the Cell Cytoplasm

Prokaryotic Cell Membrane


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Facilitated Diffusion


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Adjacent lipid tails are bound together forming a lipidmonolayer, instead of a bilayer

Fatty acids are usually absent

Hydrophobic lipid tails are attached to glyceroldifferently in archaea

The Archaeal Cell Membrane Differs from Bacterial andEukaryotic Membranes

Archaeal Cell Membranes


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The Cell Cytoplasm and Internal Structures

N l id


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The nucleoid is a central subcompartment in the cytoplasmwhere DNA aggregates

The nucleoid represents a subcompartment containing thechromosome

Nucleoid


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Most cells have only one copy of each gene(are haploid), so cannot undergo mitosis likeeukaryotes

The complete set of genes is called thegenome

The DNA contains the genes (hereditaryinformation)

The chromosome is usually a closed loop ofDNA and protein


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R plasmids carry genes for resistance to

antibiotics

Plasmids can be transferred between cells and

can be used as vectors in genetic engineering

Each plasmid is a closed loop, containing 5-10genes

Plasmids are molecules of DNA smaller thanthe chromosome

Plasmids Are Found in Many Prokaryotic Cells


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Magnetosomes contain crystals of magnetite or greigite, allowingcells to respond to magnetic fields

Some aquatic bacteria use gas vesicles to float on the waterssurface

Inclusion bodies store nutrients or building blocks for cellularstructures

There are hundreds of thousands of ribosomes, used for proteinsynthesis

Other Subcompartments Exist in the Prokaryotic Cytoplasm


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The Prokaryotic Cell


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End of Chapter 4

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BIO 205 Chapter 4 Powerpoint