Post on 24-Dec-2015
• Proks and euks are similar in chemical composition and reaction
• Proks lack membrane bound organelles
• Only Proks have peptidoglycan
• Euks have membrane bound organelles
• Euks have paired chromosomes
• Euks have histones
Nick sees the difference mainly in information and structural
capacity
• Proks lack membrane-enclosed organelles
• Euks are like a 2mhz 100gb home computer
• Proks are like a calculator• Human genome 4x109
• E. coli 4x106
The prokaryote
• Unicellular• Multiply by binary fission• Differentiated by
– Morphology– Chemical composition– Nutritional requirements– Biochemical activates– Sources of energy– Other tests
Size
• 0.2 to 2um in diameter
• 2-8um in length
• In biological systems there are always exceptions these are general sizes.
Shape
• Coccus– Diplococci– Streptococci– Staphylococci
• Bacillus• Spiral• Other pleomorphic
shapes
Parts not seen
• Glycocalyx– Capsule– Slime layer– Extracellular
polysaccharide
• Function• Toxicity
• Protect from phagocytosis
• Allow adherence• Reduce water loss• Collect nutrients
Flagella: long filamentous appendages with filament,
hook and basal body• Used in movement• Can present taxis
– Negative– Positive
• Monotrichous• Peritrichous• Flagellar H protein
acts as an antigen E.c O157:H7
• Flagellin
Fimbriae/pili
• Shorter and less complex than flagella
• Helps adhere to surfaces
• Used for sex and communication
Cell wall• Major difference between eukaryotic and prok orgs.• Surrounds plasma membrane provides protection• Peptidoglycan
– Polymer of• NAG
• NAM
• Short amino acid chain
• Production inhibited by antibiotics• Prevents osmotic damage• Damage to cw is almost always lethal except
Figure 4.12
Peptidoglycan
• Polymer of disaccharide:– N-
acetylglucosamine (NAG)
– N-acetylmuramic acid (NAM)
Figure 4.6
The Cell Wall
• Prevents osmotic lysis
• 4-7 Differentiate protoplast, spheroplast, and L form.
• Made of peptidoglycan (in bacteria)
• Linked by polypeptides
• Thick peptidoglycan
• Teichoic acids
Gram-positiveCell Wall
Figure 4.13b–c
Thin peptidoglycan Outer membrane Periplasmic space
Gram-positiveCell Wall
Gram neg
• Lipoprotein phospholipid outer membrane surrounding a thin peptidoglycan
• Makes gram neg resistant to– Phagocytosis– Antibiotics– Chemical reactions– Enzymes (lysozyme)– Has lipid A endotoxin– O polysaccaride antigen O157:H7 E.c.
The 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
• 2-ring basal body
• Disrupted by lysozyme
• Penicillin sensitive
Gram-PositiveCell Wall
Figure 4.13b–c
4-ring basal body Endotoxin Tetracycline sensitive
Gram-NegativeCell Wall
Nontypical cell walls
• Mycoplasma (acid fast) do not have ppt containing cell wall.
• Archaea contain another chemical called pseudomurein
Figure 24.8
Atypical Cell Walls
• Acid-fast cell walls– Like gram-positive– Waxy lipid (mycolic acid) bound to
peptidoglycan– Mycobacterium– Nocardia
Atypical Cell Walls
• Mycoplasmas– Lack cell walls– Sterols in plasma membrane
• Archaea– Wall-less or– Walls of pseudomurein (lack NAM and D-amino
acids)
Damage to the Cell Wall
• Lysozyme digests disaccharide in peptidoglycan• Penicillin inhibits peptide bridges in peptidoglycan• Protoplast is a wall-less cell• Spheroplast is a wall-less gram-positive cell
– Protoplasts and spheroplasts are susceptible to osmotic lysis
• L forms are wall-less cells that swell into irregular shapes
Plasma membrane
• Defines the living and nonliving parts of the cell– Everything on the inside is living– Everything on the outside is not living
• Is selectively permeable
• Workspace for enzymes of metabolic reactions
Plasma Membrane• Phospholipid bilayer
• Peripheral proteins
• Integral proteins
• Transmembrane proteins
Figure 4.14b
PM Workspace
– Nutrient breakdown– Energy production– Photosynthesis– Afforded by mesosomes which are regular
infoldings of the plasma membrane
• Weaknesses: destroyed by actions of alcohols, detergents and polymyxins
• Membrane is as viscous as olive oil.
• Proteins move to function
• Phospholipids rotate and move laterally
Fluid Mosaic Model
Figure 4.14b
• Damage to the membrane by alcohols, quaternary ammonium (detergents) and polymyxin antibiotics causes leakage of cell contents.
Plasma Membrane
Figure 4.17a
Movement of Materials across Membranes
• Simple diffusion: Movement of a solute from an area of high concentration to an area of low concentration
Figure 4.17b-c
Movement of Materials across Membranes
• Facilitated diffusion: Solute combines with a transporter protein in the membrane
ANIMATION Passive Transport: Principles of Diffusion
ANIMATION Passive Transport: Special Types of Diffusion
Movement of Materials across Membranes
Figure 4.18a
Movement of Materials across Membranes
• Osmosis: The movement of water across a selectively permeable membrane from an area of high water to an area of lower water concentration
• Osmotic pressure: The pressure needed to stop the movement of water across the membrane
Figure 4.17d
Movement of Materials across Membranes
• Through lipid layer
• Aquaporins (water channels)
ANIMATION Active Transport: Overview
ANIMATION Active Transport: Types
Movement of Materials across Membranes
• Active transport: Requires a transporter protein and ATP
• Group translocation: Requires a transporter protein and PEP
Cytoplasm's
• The liquid component of the cell within the PM
• Mostly water, dissolved ions, DNA ribosomes and inclusions
• Concept of homeostasis
Nuclear area
• Contains the bacterial chromosome
• Bacteria may also have plasmids with up to 25% of the genetic materials
Inclusions
• Typically reserve deposits of excess materials like inorganic phosphate
• Polysaccharide granules
• Lipids
• Sulfur
• Gas
• iron
Inclusions
• Metachromatic granules (volutin)
• Polysaccharide granules
• Lipid inclusions• Sulfur granules• Carboxysomes
• Gas vacuoles• Magnetosomes
• Phosphate reserves
• Energy reserves• Energy reserves• Energy reserves• Ribulose 1,5-diphosphate
carboxylase for CO2 fixation
• Protein-covered cylinders• Iron oxide
(destroys H2O2)
Comparison
• Flagella and cilia tubulin (9/2) arrangement
• Cell wall of different materials
• Glycocalyx
• Plasma membrane
organelles
• Nucleus• ER• 80s ribosomes• Golgi complex• Lysozymes• Vacuoles• Mitochondria• Chloroplasts• Peroxisomes
Organelles
• 4-18 Define organelle.
• 4-19 Describe the functions of the nucleus, endoplasmic reticulum, Golgi complex, lysosomes, vacuoles, mitochondria, chloroplasts, peroxisomes, and centrosomes.
Organelles
• Nucleus: Contains chromosomes
• ER: Transport network
• Golgi complex: Membrane formation and secretion
• Lysosome: Digestive enzymes
• Vacuole: Brings food into cells and provides support
Organelles
• Mitochondrion: Cellular respiration
• Chloroplast: Photosynthesis
• Peroxisome: Oxidation of fatty acids; destroys H2O2
• Centrosome: Consists of protein fibers and centrioles
• Not membrane-bound:– Ribosome Protein synthesis– Centrosome Consists of protein
fibers and centrioles– Centriole Mitotic spindle formation
Eukaryotic Cell
Membrane activity
• Diffusion
• Osmosis
• Passive diffusion
• Facilitated diffusion
• Active transport
• Know the relationships
• Active transport of substances requires a transporter protein and ATP.
• Group translocation of substances requires a transporter protein and PEP.
Movement Across Membranes