Lecture 2 Anatomy and Physiology of Prokaryotic and Eukaryotic Cells.

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Lecture 2 Anatomy and Physiology of Prokaryotic and Eukaryotic Cells

Transcript of Lecture 2 Anatomy and Physiology of Prokaryotic and Eukaryotic Cells.

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Lecture 2Anatomy and Physiology of

Prokaryotic and Eukaryotic Cells

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Prokaryotic Cells

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Bacterial Shape and Arrangement

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Streptococcus chain

© Dr. David M. Phillips/Visuals Unlimited

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Sarcinae cube

© David B. Fankhauser, University of Cincinnati, http://biology.clc.uc.edu/Fankhauser/

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Staphylococcus aureus cluster

© Dr. Fred Hossler/Visuals Unlimited

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Spiral-shaped bacterial cell

© Michael Abbey/Visuals Unlimited

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Prokaryotic Cell Structure

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Cytoplasmic Membrane

• Surrounds cytoplasm and defines boundaries of cell

• Acts as barrier, but also functions as an effective and highly discriminating conduit between cell and surroundings

• Made up of phospholipid bilayer

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Figure 4.14c

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Phospholipid

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Figure 4.14b

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Movement of Molecules through Cytoplasmic Membrane

• Several ways for molecules to move through membrane

1. Simple Diffusion

2. Osmosis

3. Facilitated Diffusion

4. Active Transport

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Simple Diffusion

• Does not require expenditure of energy

• Process by which some molecules move freely into and out of the cell

• Small molecules such as carbon dioxide and oxygen

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Microbiology: An Introduction, 9eby Tortora, Funke, Case

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

Figure 4.18: The principle of osmosis - Overview.

(a) At beginning of osmotic pressure experiment

(b) At equilibrium

(c) Isotonic solution — no net movement of water

(d) Hypotonic solution — water moves into the cell and may cause the cell to burst if the wall is weak or damaged (osmotic lysis)

(e) Hypertonic solution — water moves out of the cell, causing its cytoplasm to shrink (plasmolysis)

Glass tube

Rubberstopper

Rubberband

Sucrosemolecule

Watermolecule

Cellophanesack

Cytoplasm Solute Plasma membrane

Cell wall

Water

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Transport Proteins

• Transport proteins (or transporters) responsible for:

• Facilitated Diffusion

• Active Transport

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Microbiology: An Introduction, 9eby Tortora, Funke, Case

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

Figure 4.17: Facilitated diffusion.

Transportedsubstance

Transporterprotein

Outside

Inside

Glucose

Plasmamembrane

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Cell Wall

• Composed of peptidoglycan

• Comprised of alternating NAG and NAM molecules

• Attached to each NAM is four amino acid peptide: tetrapeptide

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Categories of Bacteria

• Two Major Categories:

• Difference due to difference in chemical structures of their cell walls– Gram positive: stains purple– Gram negative: stains red

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Gram + Cell Wall

• Thick Layer of Peptidoglycan

• Contains techoic acid: chains of ribitol-phosphate or glycerol-phosphate to which sugars or alanine attached

• Techoic Acid sticks out above the peptidoglycan layer

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Gram – Cell Wall

• More complex than Gram + cell wall

• Thin layer of peptidoglycan– Sandwiched between the cytoplasmic

membrane and outer membrane

• Outside of peptidoglycan is outer membrane

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Figure 4.13c

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Outer Membrane

• Unlike any other membrane in nature

• A lipid bilayer with the outside layer made of lipopolysaccharides instead of phospholipids

• Also called LPS

• Contains Porins

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Periplasm

- Region between cytoplasmic membrane and the outer membrane

- Gel-like fluid

• Filled with secreted proteins and enzymes

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External Structures

• Glycocallyx

• Flagella

• Axial Filaments

• Fimbrae and Pili

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Glycocallyx

• Gel-like structure– Functions in protection and attachment– Two types- capsule and slime layer– Involved in attachment, enabling bacteria to

stick to teeth, rocks– Enables bacteria to brow as biofilm

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Capsule in Acinetobacter species by gram negative staining

Courtesy of Elliot Juni, Department of Microbiology and Immunology, The University of Michigan

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Filamentous Protein Appendages

• Anchored in membrane and protrude from surface

• Flagella: long structure responsible for motility

• Fimbrae and Pili: shorter, responsible for attachment

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Four types of bacteria with flagella

• Montrichious- one flagella

• Amphitrichous- flagella at both ends

• Lophitrichous- many flagella at the end of the cell

• Peritrichous- flagella all over entire cell

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Figure 4.7 - Overview

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Movement of Bacteria

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Axial Filament

• Present in Spirochetes

• Attach at end of cell, spiral around, underneath an outer sheath

• Move like a corkscrew

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Figure 4.10 - Overview

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Fimbrae and Pili

• Shorter and surround the cell• Similar structural theme to filament of

flagella• Fimbrae- enable cell to adhere to surfaces,

including other cells• Pili- join bacterial cells in preparation for

the transfer of DNA from one cell to another

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Internal Structures of Prokaryotic Cells

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Cytoplasm

• Substance of cell inside the cytoplasmic membrane

• About 80% water

• Thick, aqueous, semitransparent, elastic

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Chromosome

• Found within a central location known as nucleoid

• Single, circular, double stranded

• Consists of all DNA required by cell

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Plasmids

• Some bacteria contain plasmids- small circular double-stranded DNA

• Typically cell does not require genetic information carried on plasmid

• However, it may be advantageous

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Ribosomes

• Site of protein synthesis

• Relative size and density of ribosomes and their subunits expressed as distinct unit (S)

• Two units of prokaryotic ribosomes: 50S + 30S= 70S

• Eukaryotic ribosomes: 80S

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Microbiology: An Introduction, 9eby Tortora, Funke, Case

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

Figure 4.19: The prokaryotic ribosome.

(a) Small subunit (b) Large subunit (c)

50S

50S

30S 30S

(c) Complete 70S ribosome

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Inclusions

• Store excess nutrients

• Examples: Polysaccharide granules- glycogen and starch

• Lipid inclusions

• Metachromatic granules- inorganic phosphate that can be used to synthesize ATP

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Endospores

• Occurs in members of genera Bacillus and Clostridium

• Dormant cell produced by a process called Sporulation

• Germination- when they exit the dormant state and then become a vegetative cell

• Several species of endospore formers can cause disease

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Eukaryotic Cells

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Plasma Membrane

• Very similar in structure and function to cytoplasmic membrane of prokaryotes

• Differences in types of proteins found in membranes

• Also contain carbohydrates, sterols

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External Structures

• Cell wall: much simpler then prokaryotic cell walls, no peptidoglycan

• Glycocallyx: sticky carbohydrate

• Flagella: long in relation to size of cell

• Cilia: numerous and short

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Internal Structures

• Cytoplasm

• Ribosomes

• Organelles

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Ribosomes

• Attached to surface of endoplasmic reticulum or free floating

• 40S + 60S 80S

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Organelles

• Structures with a specific shape and specialized function

• Nucleus: DNA found here

• Endoplasmic reticulum

• Golgi complex

• Lysosomes

• Mitochondria: ATP production