Why are prokaryotes the most abundant organisms on Earth?
They adapt quickly due to fast reproduction, high mutation rates, and short generation times.
What are the three main shapes of prokaryotes?
Cocci (spherical), Bacilli (rod-shaped), Spirals (spiral-shaped).
What is the function of the prokaryotic cell wall?
Maintains shape, protects the cell, prevents bursting in hypertonic environments.
What is peptidoglycan?
A polymer of sugars and polypeptides found in bacterial cell walls.
Gram-positive vs Gram-negative bacteria?
Gram-positive: thick peptidoglycan, simpler wall. Gram-negative: thin peptidoglycan + outer membrane; more antibiotic resistant.
Why are Gram-negative bacteria often more dangerous?
Their outer membrane protects them from antibiotics and immune defenses.
What is the function of a capsule/slime layer?
Helps adhesion, prevents dehydration, shields from immune system.
What is an endospore?
A highly resistant dormant structure protecting bacterial DNA in harsh conditions.
What is taxis?
Movement toward or away from a stimulus.
Do prokaryotes and eukaryotes have the same chromosome structure?
No: Prokaryotes have circular chromosomes; eukaryotes have linear chromosomes.
What is a plasmid?
A small, independently replicating DNA ring in prokaryotes, DISTINCT from bacterial chromosomal DNA
What are the three mechanisms of horizontal gene transfer in prokaryotes?
Transformation, transduction, and conjugation.
What is the F factor?
DNA that enables conjugation; F+ are donors, F- are recipients.
What are R plasmids?
Plasmids carrying antibiotic resistance genes.
What are the four major nutritional modes?
Photoautotroph, Chemoautotroph, Photoheterotroph, Chemoheterotroph.
Obligate aerobe vs obligate anaerobe vs facultative anaerobe?
Obligate aerobes need O2; obligate anaerobes are poisoned by O2; facultative anaerobes use O2 when available.
What is nitrogen fixation?
Converting atmospheric N2 into ammonia (NH3).
What are heterocysts?
Specialized cells that perform nitrogen fixation; thick walls keep oxygen out.
What are biofilms?
Surface-coating microbial colonies in a slimy layer, e.g., dental plaque.
What are proteobacteria?
A diverse group of gram-negative bacteria including auto-, chemo-, and heterotrophs.
What are chlamydias?
Gram-negative bacteria lacking peptidoglycan; survive only in animal cells.
What characterizes spirochetes?
Gram-negative heterotrophs that move using flagellum-like filaments.
What makes cyanobacteria essential?
Gram-negative photoautotrophs; perform plant-like photosynthesis; some fix nitrogen.
What types of organisms are in the gram-positive bacteria group?
Includes pathogens, soil decomposers, and antibiotic producers.
