Describe the 4 major processes of living cells.
- Growth- increase in size and complexity
- Reproduction- production of new cells or of a new individual. sexual/asexual
- Responsiveness- ability to detect changes (stimuli) in external or internal environment and respond to them.
- Metabolism- all chemical reactions that occur within a cell- all living things transform matter and energy to live
How are prokaryotic and eukaryotic cells the same?
- Both are surronded by a plasma membrane (phospholipid bilayer) that defines their boundaries.
- Both encode genetic information in DNA molecules.
How are prokaryotic and eukaryotic cells different?
Eu has nucleus and Pro does not Eu has nucleolus and Pro does not Eu has cytoskelton and Pro does not Eu divides by mitosis or meosis and Pro divides by binary fission Eu has histones and Pro does not
Describe the function of the glycocalyx.
– Enables certain bacteria to resist phagocytic
engulfment by white blood cells
– Enables some bacteria to adhere to
environmental surfaces to colonize and resist
flushing (rocks, human teeth)
– Protects against dehydration (dessication)
Describe the clinical significance of the glycocalyx.
Streptococcus pneumoniae
– Pathogenic with capsule
– Nonpathogenic without capsule
What are flagella?
Long filamentous
appendages that
function in propelling
the bacterium
What are the 3 basic parts of the flagella?
-Filament – rigid, extends from cell surface (flagellin protein)
– Hook – flexible coupling between filament and basal body
– Basal body – a rod and series of rings that anchor the flagellum and the cytoplasmic membrane molecular motor that enables flagellum rotation
Flagella arrangements:
Monotrichous-single flagellum, at one pole
Amphitrichous- single flagellum, at both poles
Lophotrichous- two or more flagellum at one or both poles
Peritrichous- flagella over entire surface
Flagellar Function
• Locomotion (for most of bacteria capable of
motility)
Clinical Significance of Flagella
H pylori (the causative agent for some forms of gastric ulcers in humans.
Describe positive chemotaxis, negative chemotaxis, positive phototaxis and negative phototaxis in relationship to a microbe’s motility.
Positive chemotaxis- move toward chemical ex pheromoes
Negative chemotaxis- move away from chemical ex fart on elevator
Positive phototaxis- move toaward light ex. photosynthesis or food
Negative phototaxis- move away from light ex. so it doesnt harm it or somethng moving toward light doesnt harm or kill organism
Fimbriae (Attachment Pili)
attachment pili, hair-like projections found in many gram-neg bacteria, used for attachment not movement, found at poles to hlep bacteria adhere to surfaces.
- Contribute to pathogenicity
- Clinically significant in N gonorrhoeae and E coli
Pili
Conjugation (sex) pili
– Found only in certain groups of bacteria
– Attaches two cells to provide a pathway to
transfer genetic material (conjugation)
– Important mechanism of transferring antibiotic
resistance.
The extra gene is used for antibiotic resistance. Can make hospital antibiotic resistance
Axial Filament
- cork screw motion, screw into skin
- extend from both ends of bacterium between outer membrane and cell wall.
- Clinically significant: can bore through tissue as in Treponema pallidum (causative agent of syphilis) and B burgdorferi (lyme disease)
Describe the chemical composition of peptidoglycan
- 10-65 NAG/NAM molecules joined in chain (glycan)
- Parallel chains held together by peptide cross bridges
- sugars in the body are in D form/ amino acids are in L form
Gram –Positive Cell Walls
- Very thick peptidoglycan
- Lipoteichoic acid (link to plasma membrane)
- Teichoic acid (linked to peptidoglycan)
- Stains purple
Gram- Negative Cell Walls
- Very few layers of peptidoglycan
- Outer membrane – LPS, lipoproteins, phopholipids
- Fluid-filled space between outer and plasma membrane
- Contains digestive enzymes and transport proteins
Lipid A
Endotoxin
toxicity or poisining to patient seen as flu symptoms/ DIC
Describe the differences of the cell walls of bacterial, archaeal, mycoplasma and L-forms.
Bacteria: semi rigid, lies outside of cell membrane, often porous, does not regulate the entry of materials into or out of the cell, composed of peptidoglycan
Archaea: lack cell walls or unique cell walls (no peptidoglycan)
Mycoplasma: do not have cell walls- unique plasma membranes (sterols)
L-forms: can live with or without their cell walls- they have cell walls and then lose their ability to make them
Clinical significance of L-forms
- they turn gene genesis off making it difficult to treat.
- may play a role in recurent chronic disease
- often results from treatment or antibiotics specific for cell destruction
Describe the function and clinical significance of biofilms.
Function: impede or inibit antimicrobial drugs and allow bacteria to retain nutreints
CS: make treatment much more difficult and prolonged
Explain the fluid mosaic model of cytoplasmic membrane structure.
Selectively permable conduit, both hydrophillic and hydophobic, highly dynamic and organized, loaction of variety of critical metabolic processes
Describe the prokaryotic cytoplasm and its basic content
- 80% water
- Proteins, carbohydrates, lipids
- Inorganic ions
- Inclusions
- Ribosomes
- Nuclear area
Describe the basic structure, function and clinical significance of prokaryotic ribosomes.
- translation and proteins synthesis*
- protein and rRNA
- Streptomycin inhibits protein synthesis by attaching to 30S subunit
