Biol 2420 Exam 1 Study Questions and Correct Answers
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Course
BIO 2420
Institution
BIO 2420
Coccus (cocci) Round, berry shaped, can be oval, pointed, or kidney-shaped
Bacillus (bacilli) Rod-shaped, can be pointed or filamentous
Spirilla Spirilla, spirochetes, or vibrios
Pleomorphic Vary in shape and size and do not have a cell wall. Difficult to treat because without a cell wall, a gra...
Biol 2420 Exam 1 Study Questions and
Correct Answers
Coccus (cocci) ✅Round, berry shaped, can be oval, pointed, or kidney-shaped
Bacillus (bacilli) ✅Rod-shaped, can be pointed or filamentous
Spirilla ✅Spirilla, spirochetes, or vibrios
Pleomorphic ✅Vary in shape and size and do not have a cell wall. Difficult to treat
because without a cell wall, a gram stain can't be done, so difficult to predict what
antibiotic to use for treatment.
Diplococci ✅Cocci that remain attached
Streptococci ✅Long chains of cocci
Tetrads ✅Cocci that divides in 2 planes and remain attached
Sarcinae ✅Cocci that divides in 3 planes to form cuboidal packets (cube of 8)
Staphylococci ✅Cocci that look like bunches of grapes, planes of division are random
Diplobacilli ✅Rods that remain attached, end to end
Streptobacilli ✅Long chains of bacilli, like chain of sausages
V shapes ✅Daughter cells remain hinged together from snapping division
Palisade ✅Side by side arrangements of bacilli, like hot dogs in a package
Binary fission - 5 steps ✅Entire process takes about 30 minutes on average
1. Cell replicates its DNA which is attached to cell membrane
2. Cell elongates to move the 2 DNA molecules apart
3. Cell forms a cross wall, invaginating the cytoplasmic membrane
4. Cross wall completely divides the daughter cells
5. Daughter cells may or may not separate
Endospore formation ✅Occurs only in certain Gram positive rods like Clostridium and
Bacillus. Endospore formation occurs when the bacteria is exposed to very unfavorable
conditions.
, 1. Sporulation begins when 1 or more nutrients are in limited supply, occurs in 8-10
hours
2. During spore formation, 2 membranes are formed, they are thick layers of
peptidoglycan and a spore coat form around a copy of the cells DNA
3. Large amounts of dipicolinic acid (enzyme stabilizer), calcium and DNA binding
proteins are deposited while most of the water is removed
Endospore characteristics ✅Spores can be found in 3 places: centrally (middle),
subterminally (in between middle and end), or terminally (end)
They are extremely resistant to heat, desiccation, radiation, and lethal chemicals
Spores are in a state of suspended animation and germinate when conditions improve
Serious concern to food industry, health care, governments because spores do not
respond to treatments that would kill a vegetative cell
Flagella ✅A flagellum is a long, whip-like structure that extends beyond the cell like
hairs
Many rods and spiral bacteria are capable of independent motion through flagellum
Composed of long, rigid strands of protein subunits called flagellin, within the strands
the protein exists in ultra thin fibers permanently bent like a coil or helix, allowing the
flagellum to rotate
Bacterial flagella are anchored at the cell membrane by a basal region consisting of a
hook-like structure and a basal body, the basal body has a central rod and a set of
enclosing protein rings
Movement that occurs in response to a stimulus like light or chemical is called taxis
Filament, hook and basal body: the hook allows the filament to rotate.
Four arrangements of bacterial flagella ✅1. Monotrichous is a single polar flagellum
2. Lophotrichous has a group of flagella at one pole
3. Amphitrichous has a group of flagella at each pole
4. Peritrichous has flagella distributed over the entire cell
Fimbriae ✅Nonmotile extensions on gram negative bacteria that are sticky,
proteinaceous and bristle like. Contain proteins called adhesions and each cell may
have hundreds. They anchor bacteria to surfaces such as living tissue
Pili ✅Composed of protein subunits called pilin
Sex pili ✅Aid the transfer of genetic material among bacteria, usually only 1-2 per cell
Glycocalyx ✅An adhering layer of polysaccharides and small proteins produced and
secreted by the bacteria to the outside of the cell for protection
Capsule ✅The glycocalyx is thick and tightly bound to the cell and cannot be easily
engulfed by WBC's which is an important component in bacterial virulence
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