Prokaryotic & eukaryotic cells 3

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Functional Anatomy of Functional Anatomy of Prokaryotic and Eukaryotic Prokaryotic and Eukaryotic Cells Cells

Transcript of Prokaryotic & eukaryotic cells 3

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Functional Anatomy of Prokaryotic Functional Anatomy of Prokaryotic and Eukaryotic Cellsand Eukaryotic Cells

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• Prokaryote comes from the Greek words for prenucleus

• Eukaryote comes from the Greek words for true nucleus.

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Prokaryote Eukaryote

• One circular chromosome, not in a membrane

• No histones

• No organelles

• Peptidoglycan cell walls

• Binary fission

• Paired chromosomes, in nuclear membrane

• Histones

• Organelles

• Polysaccharide cell walls

• Mitotic spindle

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ProkaryoteProkaryote

• One circular chromosome, not in a membrane

• No histones• No organelles• Peptidoglycan cell walls• Binary fission

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EukaryoteEukaryote

• Paired chromosomes, in nuclear membrane• Histones• Organelles• Polysaccharide cell walls• Mitotic spindle

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Prokaryote

• Average size: 0.2 -1.0 µm 2 - 8 µm• Basic shapes

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Arrangements

1. Coccus – “ Berry”, round, oval

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2. Bacilli – Diplobacilli, Streptobacilli, Coccobacilli

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3. Spirals / Spirochetes – have 1 or more twist

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Structures External to the Cell wall

• 1. Glycocalyx• 2. Flagella• 3. Axial Filaments• 4. Fimbria• 5 Pilus

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Glycocalyx

• Outside the cell wall• Usually sticky

2 types:

1. Capsule - neatly organized

2. Slime Layer - unorganized & loose• Extracellular polysaccharide allows cell to attach• Capsules prevent phagocytosis ( Virulence Factor)•

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Flagella

• Outside cell wall, for Locomotion• Made of chains of flagellin• Attached to a protein hook

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Axial Filaments

• Endoflagella, For Locomotion• In spirochetes ( Treponema pallidum)• Anchored at one end of a cell• Rotation causes cell to move

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Fimbria & Pilus

• Fimbriae - allow attachment (Neisseria

gonorrhea)

- hairlike, short

• Pili - used to transfer DNA from one cell to

another ( Sex pili)

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Cell Wall

• Complex, Semi-rigid structure

1. Protects the interior of the cell (prevents osmotic lysis)

2. Maintains the shape

3. Point of anchorage of Flagella

Made of peptidoglycan (in bacteria), Virulence

Factor

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Peptidoglycan

- Polymer of disaccharideN-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)

- Linked by polypeptides

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Gram-Positive cell walls

• Thick peptidoglycan• Teichoic acids• In acid-fast cells, contains mycolic acid• May regulate movement of cations• Polysaccharides provide antigenic variation

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Gram-Negative Outer Membrane

• Thin peptidoglycan• No teichoic acids• Outer membrane• Lipopolysaccharides, lipoproteins, phospholipids• Protection from phagocytes, complement,

antibiotics

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Gram Stain Mechanism

Crystal violet-iodine crystals form in cell

Gram-positive

- Alcohol dehydrates peptidoglycan

- CV-I crystals do not leave

Gram-negative

- Alcohol dissolves outer membrane and leaves holes in peptidoglycan

- CV-I washes out

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Structures Internal to the Cell Wall

• 1. Plasma Membrane• 2. Cytoplasm• 3. Nuclear area• 4. Ribosomes• 5. Inclusion bodies• 6. Endospores

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Plasma Membrane / Cytoplasmic Membrane

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• Phospholipid bilayer• Peripheral proteins• Integral proteins• Transmembrane proteins

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• Selective permeability allows passage of some molecules

Large molecules – inhibited

Small molecules – allowed to pass

- H+, O, Lipid soluble• Damage to the membrane by alcohols,

quaternary ammonium (detergents) and polymyxin antibiotics causes leakage of cell contents.

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Movement Across Membranes

• Simple diffusion – Movement of a solute from

an area of high concentration

to an area of low

concentration.• Facilitative diffusion - Solute combines with a

transporter protein in the

membrane.

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• Osmosis

Movement of water across a selectively permeable membrane from an area of high water concentration to an area of lower water

Osmotic pressure

The pressure needed to stop the movement of water across the membrane.

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Cytoplasm

• Cytoplasm is the substance inside the plasma membrane

- 80% water, proteins, CHON, Lipids

inorganic ions

- where the nuclear area, ribosomes

& ribosomes are found.

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Nuclear Area

• Stores the bacterial genetic information.• No nuclear envelope• Attached to plasma membrane• Bacterial Chromosomes

- single, long, continuously arranged double

stranded DNA.• Plasmid

- small, circular double stranded DNA

separate from chromosomal DNA capable

of replicating

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• Function of Plasmids:

1. Genes for antibiotic resistance

2. Tolerance to toxic metals

3. Production of toxins

4. Synthesis of enzymes

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Ribosomes

• Circular, Site of protein synthesis• Site for antibiotic attachment

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Inclusions

• Metachromatic granules • Polysaccharide granules• Lipid inclusions• Sulfur granules• Magnetosomes

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Endospores

• Resting cells, formed when essential nutrients are depleted

• Resistant to desiccation, heat, chemicals• Bacillus, Clostridium• Sporulation: Endospore formation• Germination: Return to vegetative state

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Eukaryotic Cells

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Flagella and Cilia

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Cell Wall

• Cell wall

Plants, algae, fungi

Carbohydrates• Cellulose, chitin, glucan, mannan• Glycocalyx

Carbohydrates extending from animal plasma membrane

Bonded to proteins and lipids in membrane

No Peptidoglycan

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Plasma Membrane

• Phospholipid bilayer• Peripheral proteins• Integral proteins• Transmembrane proteins• Sterols• Glycocalyx carbohydrates• Selective permeability allows passage of some

molecules• Simple diffusion• Facilitative diffusion• Osmosis• Active transport

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• Endocytosis• Phagocytosis: Pseudopods extend and engulf

particles• Pinocytosis: Membrane folds inward bringing in

fluid and dissolved substances

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Organelles• Membrane-bound:• Nucleus Contains chromosomes• ER Transport network• Golgi complex Membrane formation and

secretion • Lysosome Digestive enzymes• Vacuole Brings food into cells/stores • Mitochondrion Cellular respiration• Chloroplast Photosynthesis• Peroxisome Oxidation of fatty acids;

destroys H2O2

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Nucleus

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Endoplasmic Reticulum

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Golgi Complex

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Lysosomes

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Mitochondrion

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Chloroplast