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