Prokaryotic & eukaryotic cells 3
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Transcript of Prokaryotic & eukaryotic cells 3
Functional Anatomy of Prokaryotic Functional Anatomy of Prokaryotic and Eukaryotic Cellsand Eukaryotic Cells
• Prokaryote comes from the Greek words for prenucleus
• Eukaryote comes from the Greek words for true nucleus.
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
ProkaryoteProkaryote
• One circular chromosome, not in a membrane
• No histones• No organelles• Peptidoglycan cell walls• Binary fission
EukaryoteEukaryote
• Paired chromosomes, in nuclear membrane• Histones• Organelles• Polysaccharide cell walls• Mitotic spindle
Prokaryote
• Average size: 0.2 -1.0 µm 2 - 8 µm• Basic shapes
Arrangements
1. Coccus – “ Berry”, round, oval
2. Bacilli – Diplobacilli, Streptobacilli, Coccobacilli
3. Spirals / Spirochetes – have 1 or more twist
Structures External to the Cell wall
• 1. Glycocalyx• 2. Flagella• 3. Axial Filaments• 4. Fimbria• 5 Pilus
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)•
Flagella
• Outside cell wall, for Locomotion• Made of chains of flagellin• Attached to a protein hook
Axial Filaments
• Endoflagella, For Locomotion• In spirochetes ( Treponema pallidum)• Anchored at one end of a cell• Rotation causes cell to move
Fimbria & Pilus
• Fimbriae - allow attachment (Neisseria
gonorrhea)
- hairlike, short
• Pili - used to transfer DNA from one cell to
another ( Sex pili)
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
Peptidoglycan
- Polymer of disaccharideN-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)
- Linked by polypeptides
Gram-Positive cell walls
• Thick peptidoglycan• Teichoic acids• In acid-fast cells, contains mycolic acid• May regulate movement of cations• Polysaccharides provide antigenic variation
Gram-Negative Outer Membrane
• Thin peptidoglycan• No teichoic acids• Outer membrane• Lipopolysaccharides, lipoproteins, phospholipids• Protection from phagocytes, complement,
antibiotics
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
Structures Internal to the Cell Wall
• 1. Plasma Membrane• 2. Cytoplasm• 3. Nuclear area• 4. Ribosomes• 5. Inclusion bodies• 6. Endospores
Plasma Membrane / Cytoplasmic Membrane
• Phospholipid bilayer• Peripheral proteins• Integral proteins• Transmembrane proteins
• 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.
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.
• 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.
Cytoplasm
• Cytoplasm is the substance inside the plasma membrane
- 80% water, proteins, CHON, Lipids
inorganic ions
- where the nuclear area, ribosomes
& ribosomes are found.
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
• Function of Plasmids:
1. Genes for antibiotic resistance
2. Tolerance to toxic metals
3. Production of toxins
4. Synthesis of enzymes
Ribosomes
• Circular, Site of protein synthesis• Site for antibiotic attachment
Inclusions
• Metachromatic granules • Polysaccharide granules• Lipid inclusions• Sulfur granules• Magnetosomes
Endospores
• Resting cells, formed when essential nutrients are depleted
• Resistant to desiccation, heat, chemicals• Bacillus, Clostridium• Sporulation: Endospore formation• Germination: Return to vegetative state
Eukaryotic Cells
Flagella and Cilia
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
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
• Endocytosis• Phagocytosis: Pseudopods extend and engulf
particles• Pinocytosis: Membrane folds inward bringing in
fluid and dissolved substances
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
Nucleus
Endoplasmic Reticulum
Golgi Complex
Lysosomes
Mitochondrion
Chloroplast