MICROBIO:3
Cards (20)
- Characteristics of a prokaryotic cell:
- DNA is not enclosed within a membrane and is usually a singular circularly arranged chromosome
- DNA is not associated with histones
- Lacks membrane-enclosed organelles
- Cell walls almost always contain peptidoglycan
- Usually divides by binary fission
- Characteristics of a eukaryotic cell:
- DNA is found within the nucleus, separated from the cytoplasm by a nuclear membrane
- DNA is consistently associated with histones
- Contains membrane-enclosed organelles like mitochondria, endoplasmic reticulum, Golgi complex, and lysosome
- If present, cell walls are chemically simple
- Cell division usually involves mitosis
- Basic shapes of bacteria:
- Bacteria come in various sizes and shapes, ranging from 0.2-2.0 μm in diameter & 2-8 μm in length
- Basic shapes include spherical Coccus (pleural: cocci), rod-shaped Bacillus (pleural: bacilli), and Spirals (including vibrios, spirillas & spirochetes)
- Polymorphism in bacteria:
- Polymorphic bacteria can have many shapes, like Corynebacterium and Rhizobium
- Structures external to the cell wall in bacteria:
- Glycocalyx
- Flagella
- Axial filaments
- Fimbriae
- Pili
- Functions of glycocalyx in bacteria:
- A "sticky" coating made up of polysaccharide surrounding the cell membranes
- Serves as a glue that holds cells in place such as those in biofilms
- Functions of flagella in bacteria:
- Long filamentous appendages that propel bacteria
- Consist of filament, hook, and basal body
- Enable various patterns of motility
- Functions of fimbriae and pili in bacteria:
- Hair-like appendages used for attachment and transfer of DNA to another bacterium
- Fimbriae are for adherence to each other & different surfaces
- Pili are involved in motility (twitching motility) & DNA transfer
- Composition of the bacterial cell wall:
- Composed of a network of peptidoglycan, consisting of a repeating disaccharide attached by polypeptides to form a lattice
- Alternating NAM and NAG molecules are linked in rows of 10-65 sugars to form a carbohydrate "backbone"
- Gram classification of bacteria:
- Gram stain is a method for classifying bacteria based on their cell wall
- Gram-positive bacteria have many layers of peptidoglycan, forming a thick, rigid structure
- Gram-negative bacteria have only a thin layer of peptidoglycan
- Prokaryotic cell structures:
- Cell membrane
- Cytoplasm (80% water & 20% compounds like proteins, carbohydrates, lipids, & inorganic ions)
- Nucleoid (region with bacterial chromosome)
- Ribosomes
- Inclusions
- Nucleoid contains the bacterial chromosome, a single long continuous thread of double-stranded DNA
- Plasmids are small circular DNA molecules in the cytoplasm not connected to the main bacterial chromosome, associated with proteins of the plasma membrane
- Ribosomes are cytoplasmic structures for protein synthesis, composed of 30S and 50S subunits
- Endospores are specialized "resting" forms of certain bacteria during nutrient depletion, occurring in Gram-positive bacteria like Clostridium & Bacillus
- Eukaryotic flagella & cilia:
- Used for locomotion
- Eukaryotic flagella move in a wave-like manner
- Eukaryotic flagella & cilia consist of 9 pairs of microtubules arranged in a 9+2 array
- Eukaryotic cell walls are simpler than prokaryotic cell walls, with plant cell walls made of cellulose, fungal cell walls of chitin, and yeast cell walls of glucan & mannan
- Eukaryotic plasma membrane is similar in function & structure to prokaryotes but contains sterols, allows endocytosis, and has carbohydrates serving as receptors for cell-to-cell interactions
- Eukaryotic ribosomes are sites of protein synthesis, larger than prokaryotic ribosomes (80S), and can be free in the cytoplasm or attached to the rough endoplasmic reticulum
- Eukaryotic organelles include the nucleus, endoplasmic reticulum, Golgi complex, mitochondria, lysosomes, vacuoles, chloroplasts, peroxisomes, and centrosomes