Structure of Prokaryotic & Eukaryotic Cells

Review of Prokaryotic & Eukaryotic Cells Nucleus vs nucleoid DNA : circular vs linear, presence of histones Membranous organelles Cell wall-peptidoglycan Cell division: binary vs mitosis Ribosomes: 70S vs 80S Cytoskeleton

Shape Cocci –Diplococci –Streptococci –Tetrads –Sarcinae –Staphylococci

Bacillus Coccobacilli Diplobacilli Streptobacilli

Spiral Vibrio-curved rods Spirilla-helical & rigid Spirochetes-helical & flexible Other shapes Pleomorphic

Glycocalyx Glycolipids or glycoproteins Surrounds cell Capsule or slime layer Capsule more organized & attached to wall Advantages of capsule

Slime Layer(Biofilm) Surrounds cell Loosely organized & not attached Tangled mass of fibers-dextran Attachment to surfaces -S. mutans Shields bacteria from immune defense & antibiotics

Glycocalyx -Eukaryotes Animal cells have one Made of carbohydrates No do not have a cell wall Surround plasma membrane Stabilizes PM

Flagella Movement –Spins like propeller –Clockwise or counter clockwise Chemotaxis- movement toward or away

Arrangements Monotrichous: one at end Amphitrichous: both ends Lophotrichous: tuft at end or ends Peritrichous: around the cell

Structure Composition-protein subunits: flagellin (H protein) E. coli H7 –Chains twisted together with hollow core –Helical shaped –Filament, hook, basal body –Hook –Basal body:

Flagella Basal body Classified by flagella protein

Axial Filament Spirochetes –Treponema pallidum-syphilis –Borrelia burgdorferi-Lyme disease Bundle of fibrials within a sheath Corkscrew motion

Movement Eukaryotes Flagella & cilia –9+2 arrangement of microtubules –Cilia in Paramecium & respiratory cells

Prokaryote Fimbriae & Pili Made of pilin: string of subunits Function: attachment Few to hundreds Fimbrae Pili-longer & fewer Not in eukaryotes

Cell Wall Function Basis of Gram stain

Composition Peptidoglycan –Repeating subunits of disaccharides N-acetyl glucosamine (NAG) N-acetyl muramic acid (NAM) Linked alternately in rows –Attached by polypeptides Tetrapeptide side chains link NAM subunits Cross bridge of amino acids link tetrapeptides –Forms lattice

Peptidoglycan Confers shape & prevents lysis Cell growth –Autolysins break cross linkages in peptidoglycan –Transpeptidases seal breaks –Penicillin inactivates these enzymes Existing cells –Treat with lysozyme-tears, saliva etc. –Destroys linkages between carbohydrates

Gram Positive Cell Wall Thick layers: 40-80% of dry wt, up to 30 layers Contains teichoic acid –Alcohol and phosphate –Negative charge –Cell growth-prevents lysis –Antigenic properties

Gram Negative Cell Wall Few layers of peptidoglycan- 10% Outer membrane: bilayer Periplasm

LPS Strong negative charge Barrier to some antibiotics Outer membrane-endotoxin –O polysaccharides –Lipid-lipid A

Gram Stain Differential stain dev by Hans Gram 1880s –Classifies bacteria into 2 groups –Based upon cell wall composition –Gram variable stain unevenly –Gram non reactive do not stain or stain poorly

Comparison Gram positives

Gram Negatives ETOH disrupts outer layer CV-I complex is washed out of thin peptidoglycan layer Counterstain

Atypical Cell Walls Streptococci Mycobacteria Mycoplasma –PM unique with sterols protect from lysis

Mycoplasma Lack a cell wall so pleomorphic Classified with gram positives Smallest genome of any bacteria Droplet spread-use regular mask Why can’t you use penicillin?

Cell wall of Eukaryotes Simpler than prokaryotes Algae & plants Fungi Yeasts Protozoa Animals

Plasma Membrane Thin, fluid structure inside cell wall-viscous Proteins Phospholipids-2 layers

Functions of Membrane Selective permeability Passive transport: Active transport: Enzymes break down nutrients Infoldings

Plasma Membrane of Eukaryotes Phospholipids and proteins Carbohydrates and sterols-cholesterol More rigid than prokaryotic PM Endocytosis Exocytosis

Cytoplasm of Prokaryotes 80% water, thick, solutes Increase in osmotic pressure on membrane –Rigid cell wall prevents lysis Contains DNA Ribosomes Inclusion bodies

Cytoplasm of Eukaryotes Cytosol-fluid portion Cytoskelton –Microfilaments: –Microtubules: –Intermediate filaments: Cytoplasmic streaming

Ribosomes 2 subunits of protein and rRNA 70s ribosomes Polyribosomes-chains Protein synthesis Eukayotes-80s

Inclusions Polysaccharide granules Sulfur granules Reserve deposits-volutin (phosphates)

Endospores Unique to bacteria: Clostridium & Bacillus Sporulation-formation of spores

Germination Triggered by damage to coat Enzymes break down endospore Water enters & metabolism begins Not a reproductive structure

Nuclear Area of Bacteria Single, ds DNA chromosome Attached to PM at some point Nucleoid area, not a nucleus Plasmids

Nucleus Largest structure in cell –Nucleoli DNA associated with proteins -histones

Organelles in Eukaryotes Unique to eukaryotes Membranous structures –Endoplasmic reticulum Smooth & rough –Golgi complex –Lysosomes –Mitochondria –Cloroplasts

ER Flattened membranous sacs Rough ER-ribosomes attached Smooth ER- no ribosomes Free ribosomes- proteins don’t need processing

Golgi Complex Stacks of membranous sacs Receive transport vesicles from ER Modify molecules to form glycoproteins, glycolipids lipoproteins Transported in secretory vesicles to PM or to outside cell

Lysosomes Formed from Golgi –Contain digestive enzymes: proteases & nucleases –Break down old parts of cell –Breaks down pathogens

Mitochondria Double membrane Generation of ATP

Chloroplasts Thylakoids-flattened membranous sacs Contain DNA 70s ribosomes Stroma thick fluid in center- Calvin cycle Generation of ATP & sugars