Ch. 3 Bacteria cell structures and their functions Flashcards
(42 cards)
1
Q
How are bacteria and archaea different from eukaryotes?
A
- the way their DNA is packaged - lack of nucleus and histones
- the makeup of their cell wall - peptidoglycan and other unique chemicals
- their internal structure - lack of membrane-bound organelles
2
Q
What is pleomorphism?
A
variation in the size and shape of cells of a single species due to nutritional and genetic differences
3
Q
What are the different cocci arrangements?
A
- singular = coccus
- diplococci = pairs
- Tetrads = groups of 4
- staphylococci/ micrococci = irregular clusters
- streptococci = chains
- Sarcina = cubical packet of 8,16, or more
4
Q
What are the arrangements of Bacilli?
A
- single = bacillus
- Diplobacilli = pair of cells w/ ends attached
- Streptobacilli = chain of several cells
- Palisades = cells of a chain remain partially attached by a small hinge region at the end
5
Q
What are the spiral bacterial shapes?
A
- Vibrio = comma-shaped rods
- spirillum = rigid helices
- spirochetes = flexible helices
*almost always exist as single cells; rarely attached to another after division
6
Q
What structures are in all bacteria cells?
A
- cytoplasmic membrane
- cytoplasm
- ribosomes
- cytoskeleton
- one (or a few) chromosomes
7
Q
What structures do MOST bacterial cells
A
- cell wall
- a surface coating called a glycocalyx
8
Q
What structures are on SOME bacteria?
A
- flagella, pili, fimbriae
- an outer membrane
- plasmids
- inclusions
- endospores
- microcompartments
9
Q
What is the cell envelope and what is it made of?
A
- lies outside the cytoplasm
- composed of two or 3 basic layers that each perform a distinct function but together act as a single protective unit (cell wall, cytoplasmic membrane, outer membrane in some)
10
Q
What is the cell wall function and what is it made of?
A
- helps determine shape of bacteria
- provides strong structural support to keep the bacterium from bursting or collapsing because of changes in osmotic pressure
- Gains relative rigidity from peptidoglycan
11
Q
What are peptidoglycan’s structure and function?
A
- compound composed of repeating framework of long glycan (sugar) chains cross-linked by short peptide (protein) fragments
- provides strong but flexible support framework
12
Q
Characteristics of a gram-positive cell wall
A
- thick homogeneous sheet of peptidoglycan
- contains techoid acid and lipotechoic acid
13
Q
What are the functions of techoic and lipotechoic acid?
A
- cell wall maintenance and enlargement
- contribute to the acidic charge of cell surface
14
Q
What are the characteristics of a gram-negative cell wall?
A
- a single thin sheet of peptidoglycan
- thickness gives gram-negative cells greater flexibility and sensitivity to lysis
15
Q
What is the gram-negative outer membrane made of?
A
- similar to most membranes, except it contains specialized polysaccharide
- lipopolysaccharide (for signaling molecules/receptors; also endotoxin)
- Porin proteins (special membrane channels that only allow certain chemicals to penetrate)
16
Q
What is the structure of the cytoplasmic membrane?
A
- lipid bilayer w/ proteins embedded
- selectively permeable - special carrier mechanisms for passage of most molecules
17
Q
What is the function of the cytoplasmic membrane?
A
- regulates the transport of nutrients and wastes
- site for energy reactions, nutrient processing, and synthesis
18
Q
What are the characteristics of a gram-negative cell envelope structure?
A
- outer membrane is an extra barrier that allows it to be resistant to certain antimicrobial chemicals. Also makes it more difficult to inhibit or kill than gram-positive
- alcohol-based compounds dissolve lipids damaging the cell
19
Q
What are the appendages of bacteria?
A
Flagella and axial filaments
- used for motility
Fimbriae and pili
- used as attachment points
20
Q
What is the functions of the flagellum?
A
motility
21
Q
What are the 3 parts of the flagellum?
A
filament
hook
basal body
22
Q
What is chemotaxis?
A
Movement of bacteria in response to chemical signals
23
Q
What is positive chemotaxis?
A
movement toward a favorable chemical stimulus
24
Q
What is negative chemotaxis?
A
Movement away from a repellant
25
What is a run?
rotation of flagellum counterclockwise, resulting in a smooth linear direction
26
what is a tumble?
Reversal of the direction of the flagellum, causing the cell to stop and change course
27
What are periplasmic flagella?
internal flagellum enclosed in the space between the cell wall and the cytoplasmic membrane
- in spirochetes (wriggly locomotion due to the flagella)
28
What are fimbriae and their function?
- Small, bristle-like fibers sprouting off the surface of many bacterial cells
-Allow tight adhesion between fimbriae and epithelial cells, allowing bacteria to colonize and infect host tissues
29
What are pili and what is their function?
- small projections
- well characterized in gram-negative
30
What are sex pilis function?
- Type IV pilus can transfer genetic material, act like fimbriae and assist in attachment, and act like flagella and make a bacterium motile
31
What is the glycocalyx and their function?
- a coating of repeating polysaccharide or glycoprotein units
32
Types of glycocalyx?
- slime layer - loose, protects against water and nutrient loss
- capsule - more tightly bound, denser, thicker; produces a sticky (mucoid) character to colonies on agar
33
What is the function of a slime layer?
- protective
- involved in gliding motility
34
What are the functions of a capsule?
- protects against phagocytosis
- protects against desiccation
- have greater pathogenicity
35
What is the cytoplasm and its function?
- a complex mixture of sugars, amino acids, and salts
- 70-80% water
- serves as a pool for building blocks for cell synthesis or sources of energy
36
Where are bacterial chromosomes held?
- DNA is aggregated in the nucleoid
- the hereditary material of most bacteria exists in the bacterial chromosome
37
What are plasmids and their function?
- small nonessential pieces of DNA
- confer protective traits such as drug resistance and toxin and enzyme production
- circular or linear, independent of chromosomes
38
What is the functions of ribosomes? What is their structure?
Site of protein synthesis
- composed or rRNA and protein
- consist of a large and small subunit
39
What are inclusion bodies and microcompartments' functions?
- used for food storage
- pack gas into vesicles
- store crystal of iron oxide w/ magnetic properties
40
What are bacterial microcompartments made of?
- outer shells made of protein, arranged geometrically
- packed full of enzymes for biochemical pathways
41
What are endospores and their functions?
- Dormant bodies
- produced by bacillus, Clostridia, and Sporosarcina
- Vegetative cell that is metabolically active
- produced for cell to survive extreme conditions. Endospores resist extremes of heat, drying, freezing, radiation, and chemicals that would kill vegetative cells
42
What are some examples of medically significant endospore bacteria?
- Bacillus anthracis: agent of anthrax
- Clostridium tetani: cause of tetanus
- Clostridium perfringens: cause of gas gangrene
- Clostridium botulinum: cause of botulism
- Clostridium difficile: “C. diff,” a serious gastrointestinal disease
