Prokaryotic cells Flashcards
What are the important parts of bacteria structure
Fimbriae/pili
Cell wall
Capsule
Flagella
Describe the function of the cell wall of bacteria
Rigid macromolecular layer (peptidoglycan) - provides strength. Protects cells from osmotic lysis and keeps cell shape
Describe peptidoglycan structure
Carbohydrate backbone, consisting of alternating NAG and NAM. Held together by amino acids
What is transpeptidase
Enzyme that cross-links peptidoglycan chains to form rigid structure
Describe gram stain process
Apply crystal violet dye. Apply iodine (mordant) Alcohol wash (decolourisation) Apply safranin (counterstain)
Describe Gram-positive bacterial cell wall
Thick layer of cell wall (peptidoglycan) on top of plasma membrane - traps crystal violet stain.
Describe Gram-negative bacterial cell wall
Thin layer of cell wall (peptidoglycan) in between two membrane layers - doesn’t trap stain
Describe use of bacterial flagella
Number of flagella and location varies. Act like a propeller, turning in unison to move.
Describe structure of bacterial flagella
Long filament - Extends into surrounding median
Hook - Curved section connecting filament to cell surface
Basal body - anchors flagellum into cell membrane - disc shaped structures.
What different movement can a flagella cause
Clockwise - tumbles
Anticlockwise - Moves in a direction
How do bacteria move
Chemotaxis - along a concentration gradient towards chemical attractant (positive) or away (negative)
How does bacteria sense chemical gradient
Over time - too small to sense a spatial gradient
Describe Fimbriae
Adhesive properties that stick/adhere to surfaces. Not present on all. Small and short, alot per cell
describe glycocalyx
Sticky mesh network of fibres, outer covering, gelatinous.
What are the two types of glycocalyx
Capsule - Defined structure, attached firmly
Slime layer - Disorganised, loosely attached
