Transcript Structure of Prokaryotic & Eukaryotic Cells

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
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Glycolipids or glycoproteins
Surrounds cell
Capsule or slime layer
Capsule more organized & attached to
wall
• Advantages of capsule
Slime Layer(Biofilm)
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Surrounds cell
Loosely organized & not attached
Tangled mass of fibers-dextran
Attachment to surfaces -S. mutans
Shields bacteria from immune defense &
antibiotics
Glycocalyx -Eukaryotes
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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
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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
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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
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Selective permeability
Passive transport:
Active transport:
Enzymes break down nutrients
Infoldings
Plasma Membrane of Eukaryotes
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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
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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
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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