Lecture 2 Flashcards
(17 cards)
What are the major morphologies of prokaryotic cells?
Coccus: spherical or ovoid
Rod/bacillus: cylindrical
Spirillum: flexible spiral
Spirochete: rigid spiral
Asymmetrical
Why is cell shape important?
Cell shape affects surface area to volume ratios, which influences the efficiency of nutrient and waste product exchange. Smaller cells have a greater surface area to volume ratio, allowing for more efficient exchange per unit volume.
What is the function of the cytoplasmic membrane?
Permeability barrier prevents passive leakage of solutes in/out of the cell
Anchors proteins that catalyse key cell functions
Plays a large role in energy conservation and consumption
What is the cytoplasmic membrane?
A bilayer phospholipid membrane with embedded proteins creates a hydrophobic region, allowing for selective permeability. Some archaea have unique lipid bilayer structures that are more stable at high temperatures.
What are the 3 classes of active transport systems?
Simple: driven by H+ pump, can be transported in the same direction or opposite directions
Group translocation: driven by energy rich compound
ABC transporter: ATP-binding cassette
What is the function of the bacterial cell wall?
Withstands osmotic/turgor pressure to prevent cell lysis
Maintains cell shape and rigidity
What is the composition of the bacterial cell wall?
Bacterial cell walls are made of peptidoglycan
What are the characteristics of gram-negative bacteria?
Gram-positive bacteria have a thick peptidoglycan wall which can be 15 layers thick
What are the characteristics of gram-negative bacteria?
Gram-negative bacterial cell walls are usually just 1 layer thick and have an outer membrane
What is the outer membrane?
A second lipid bilayer around the cell wall of gram-negative bacteria that contains lipopolysaccharides (LPS), which are polysaccharide molecules covalently bound to lipids.
Why is the cell wall important for human health?
Peptidoglycan can be destroyed by lysozyme, which is found in human secretions and acts as a defence against bacterial infection. Penicillin blocks the formation of peptide cross-links in peptidoglycan.
What are capsules and slime layers?
Capsules and slime layers are structures found outside the cell wall that help cells attach to surfaces, contribute to biofilm development and maintenance, prevent dehydration, and contribute to infectivity.
What are pili?
Thin, filamentous protein structures that extend from the cell surface of all gram-negative bacteria and many gram-positive bacteria. There are several types: fimbriae (short pili involved in attachment), conjugation pili (allow genetic exchange), electrically conductive pili (conduct electrons), and type IV pili (provide twitching motility).
What is chemotaxis?
Directed movement in response to a chemical cue. Can signal access to resources or damaging conditions. Achieved through “run and tumble” movement.
What are endospores?
Highly differentiated, dormant cells resistant to heat, radiation, chemical exposure, drying, and lack of nutrients. Serve as survival structures to endure unfavourable growth conditions. Ideal for dispersal via wind, water, or animal gut. Present only in some gram-positive bacteria (e.g., Bacillales and Clostridiales).
What triggers sporulation?
Sporulation, the process of forming an endospore, is triggered by limiting nutrients.
What are the steps involved in the return to a vegetative cell from an endospore?
Germination is triggered by nutrient availability and involves three steps: activation, germination, and outgrowth.
