Lecture 2: Prokaryotic Cell Structure and Function 1 Flashcards
1
Q
Comparison between prokaryotes and eukaryotes are in my handwritten notes.
A
Know them well for the exam.
2
Q
What dictates the shape of bacteria?
A
Genome
3
Q
True or False:
Most bacteria are not monomorphic.
A
False - most bacteria are monomorphic
4
Q
What is the average size of a bacteria?
A
0.2 - 1.0 micrometers x 2 - 8 micrometers
5
Q
What does peritrichous mean?
A
It refers to flagella being all the way around the bacterium.
6
Q
What are the 3 shapes that bacteria can take?
A
- Bacillus (rod-shaped)
- Coccus (spherical)
- Spiral
- spirillum - one or more twists
- vibrio - curved rod
- spirochete - flexible, helical spirals
7
Q
What are the 3 sub-classifications of the basic bacterium shape Sprial?
A
- Spirillum -> one or more twists
- Vibrio -> curved rod
- Spirochete -> flexible, helical spirals
8
Q
Name two unusually shaped prokaryotes (that are archaea).
A
- Stella (star-shaped bacteria)
- Haloarcula, a genus of halophilic archaea (rectangular bacteria)
9
Q
What is a cluster of cocci bacteria called?
A
Staphylococci
10
Q
What is a chain of cocci or bacilli bacteria called, respectively?
A
- Streptococci
- Streptobacilli
11
Q
What is a pair of cocci or bacilli bacteria called, respectively?
A
- Diplococci
- Diplobacilli
12
Q
What does a pleomorphic organism refer to?
A
An organism that is variable in shape.
13
Q
What is a mycelium?
A
A network of long, multinucleate filaments.
14
Q
True or False:
Smaller cells have a larger surface area/volume ratio.
A
True
15
Q
List all of the common bacterial structures that you can.
A
- plasma membrane
- gas vacuole
- ribosomes
- inclusions
- nucleoid
- periplasmic space
- cell wall
- capsules and slime layers
- fimbriae and pili
- flagella
- endospores
16
Q
What structures make up the bacterial cell envelope?
A
- plasma membrane
- cell wall
- layers outside the cell wall (e.g., slime layer)
17
Q
True or False:
The plasma membrane is an absolute requirement for all living organisms.
A
True
18
Q
What is a gas vacuole?
A
An inclusion that provides buoyancy for floating in aquatic environments.
19
Q
What are inclusions?
A
Storage of carbon, phosphate, and other substances.
20
Q
What is a nucleoid?
A
Localization of genetic material (DNA).
21
Q
What is the periplasmic space of typical gram-negative bacteria? What about gram-positive?
A
- Gram-Negative Bacteria:
- contains hydrolytic enzymes and binding proteins for nutrient processing and uptake.
- Gram-Positive Bacteria:
- may be smaller or absent
22
Q
What does the cell wall protect the bacteria against?
A
- Protection from osmotic stress
- Helps maintain cell shape
23
Q
What is the function of capsules and slime layers in bacteria?
A
- resistance to phagocytosis
- adherence to surfaces
24
Q
What is the function of fimbriae and pili of bacteria?
A
- Fimbriae and Pili
- attachment to surfaces
- bacterial conjugation and transformation
- twitching motility
- gliding motility
25
What are flagella used for in bacteria?
* Swimming and Swarming Motility
26
What does the bacteria use an endospore for?
* Survival under harsh environmental conditions
27
Do bacterial membranes lack sterols (like cholesterol)?
Yes - but DO contain hopanoids, which are sterol-like molecules (e.g., bacteriohopanetetrol).
28
What do hopanoids found in the bacterial membrane function to do?
* stabilize bacterial membrane
* found in petroleum
29
What is an environmental conditions example that determines lipid composition in bacterial and eukaryotic membranes?
Temperature
30
True or False:
Many bacteria have plasma membrane infoldings.
True
31
What makes Archaeal membranes very distinctive from Bacteria and Eukaryotes?
* composed of lipids that differ chemically
* Bacterial or Eukaryotic Lipids:
* **Ester Bonds**
* 2 Hydrocarbons attached to glycerol
* Archaeal Lipids:
* **Ether Bonds**
* **Branched** molecules
* **Tetraethers** (some)
* some have a monolayer structure instead of a bilayer structure
32
What type of diethers are bilayer Archaeal membranes composed of?
* Bilayer composed of C20 Diethers
33
What type of tetraethers are monolayer Archaeal membranes composed of?
* Monolayer composed of C40 Tetraethers
34
What is the function of the plasma membrane?
* encompasses the cytoplasm
* selectively permeable barrier
* interacts with external environment
* receptors for detection of an response to chemicas in surroundings
* transport systems
* metabolic processes
35
What does the cytoplasm of Bacteria and Archaea consist of.
* Substance in which nucleoid, ribosomes, inclusion bodies, plasmids, and cytoskeletal filaments are suspended.
* LACKS organelles bound by unit membranes
* Composed largely of water
36
What is the cytoplasm of Bacteria and Archaea largely composed of?
Water
37
True or False:
Homologs of all three Eukaryotic cytoskeletal elements have been identified in Bacteria.
True
38
What are the best studied examples of bacterial cytoskeletal proteins?
* FtsZ - many bacteria
* function: forms ring during septum formation in cell division
* MreB - found in bacilli, NOT in cocci
* function: maintains shape by positioning peptidoglycan synthesis machinery
* CreS - rare
* function: maintains curve shape
39
In what type of bacteria is plasma membrane infoldings typically observed?
* observed in many photosynthetic bacteria
* observed in many bacteria with high respiratory activity
40
What is anammoxosome in Planctomycetes, and what is its function?
Organelle - site of anaerobic ammonia oxidation
41
List several organic and inorganic material that is stored in granules of inclusions.
* Storage of nutrients, metabolic end products, energy, building blocks.
* Glycogen Storage
* Carbon Storage
* poly-beta-hydroxybutyrate (PHB)
* glycogen
* Phosphate - polyphosphate granules (Volutin)
* Amino Acids - cyanophycin granules
* Sulfur Granules
42
In what type of organism are gas vacuoles found?
Found in aquatic, photosynthetic Bacteria and Archaea.
43
What does cytoskeletal protein, MamK, function to do?
Helps form magnetosome chain.
44
What are magnetosomes?
* Other inclusions
* Found in aquatic bacteria
* Magnetite particles (iron) for orientation in Earth's magnetic field
* Used by organisms to orient themselves so they know which way is up or down
45
What are microcompartments?
* NOT bound by membranes but compartmentalized for a specific function.
* Carboxysomes - CO2 fixing bacteria
* contain the enzyme ribulose-1,5,-bisposphate carboxylase (Rubisco), enzyeme used for CO2 fixation
46
What is the bacterial ribosomal RNA size?
* Bacterial and ARchaea Ribosome = 70S
* 16S small subunit
* 23S and 5S in large subunit
47
What is the size of the Eukaryotic ribosomal RNA subunit?
80S
48
What are the characteristics of the nucleoid?
* Usually not membrane bound (few exeptions)
* Location of chromosome and associated proteins
* Usually 1 closed circular, double-stranded DNA molecule
* Supercoiling and nucleoid proteins (different from histones) aid in folding
49
What are the characteristics of Prokaryotic chromosomes?
* Usually a circular, double-stranded DNA molecule
* Usually only 1
* Looped and coiled extensively
50
What are plasmids?
* extrachromosomal DNA
* found in bacteria, archaea, some fungi
* usually small, closed circular DNA molecules
* exist and replicate independently of chromosome
* episomes - may integrate into chromosome
* inherited during cell division
* contain few genes that are non-essential
* confer selective advantage to host (e.g., drug resistance)
* classification based on mode of existence, spread, and function
51
Which type of plasmids are the largest?
Metabolic Plasmids (carry genes for enzymes)
52
Which type of plasmid is the smallest?
Col Plasmids (produce bacteriocins, substances that destroy closely related species)
53
What type of plasmid transfers DNA from one cell to another?
Conjugative Plasmids
54
Which type of plasmid carries antibiotic-resistance genes?
R Plasmids
55
What is the function of Virulence Plasmids?
To carry virulence genes.
56
Does gram-positive or gram-negative cells have a thick peptidoglycan layer?
Gram-Positive
57
What color does Gram-Positive Bacterial cells stain?
Stain Purple
58
What color does Gram-Negative Bacterial cells stain?
Stain Pink or Red
59
Does Gram-Negative Bacterial Cells have a thick or thin peptidoglycan layer?
Thin peptidoglycan and outer membrane.
60
What are the functions of the cell wall?
* Maintains shape of the bacterium
* almost all bacteria cell from osmotic lysis
* Helps protect cell from osmotic lysis
* Helps protect from toxic materials
* May contribute to pathogenicity
61
Explain the peptidoglycan structure?
* Meshlike polymer of identical subunits forming long strands.
* Chains of peptidoglycan subunits are joined by cross-links (covalent bonds) between the peptides.
* Meshlike polymer of identical subunits forming long strands.
* two alternating sugars
* N-acetylglucosamine (NAG)
* N-acetylmuramic acid
* alternating D- and L-amino acids
62
What are the characteristics of gram-positive cell walls.
* composed primarily of peptidoglycan
* may also contain teichoic acids (negatively charged)
* help maintain cell envelope
* protect from environmental substances
* may bind to host cells
* some gram-positive bacteria have layer of proteins on surface of peptidoglycan
63
Which type of acid connects the cell wall to the plasma membrane?
lipoteichnoic acid
64
True or False:
Teichoic acid is like rebar in a slap of concrete.
True
65
True or False:
Peptidoglycan strands do not have a helical shape.
False - peptidoglycan strands have a helical shape.
66
Why are peptidoglycan chains crosslinked by peptides?
* For Strength
* interbridges may form
* peptidoglycan sacs - interconnected networks
* various structures occur
67
What type of peptide interbridge connects peptidoglycan strands in S. aureus? Also, between which amino acids does it link?
* 5-Glycines
* D-Alanine and L-Lysine
68
What peptidoglycan strands are crosslinked in E. coli?
D-Alanine to DAP
69
What is the characteristic of the periplasmic space of gram positive bacteria?
* lies between plasma membrane and cell wall and is smaller than that of gram-negative bacteria
* periplasm has relatively few proteins
* enzymes secreted by gram-positive bacteria are called exoenzymes
* aid in degradation of large nutrients
70
Do gram positive bacterial cells have small or large periplasmic spaces?
small periplasmic space
\* gram negative bacterial cells have a bigger periplasmic space \*
71
What are the characteristics of gram-negative cell walls?
* more complex than gram-positive
* consist of a thin layer of peptidoglycan surrounded by an outer membrane
* outer membrane composed of lipids, lipoproteins, and lipopolysaccharide (LPS)
* NO teichoic acids
* peptidoglycan is 5-10% of cell wall weight
* periplasmic space differes from that in gram-positive cells
* may constitute 20-40% of cell volume
* many enzymes present in periplasm
* hydrolytic enzymes, transport proteins and other proteins
* outer membrane lies outside that thin peptidoglycan layer
* Braun's lipoproteins connect outer membrane to peptidoglycan
* other adhesion sites reported
72
Which 3 components make up lipopolysaccharide (LPS)?
* lipid A
* core polysaccharide
* O side chain (O antigen)
73
Is lipid A embedded in the outer membrane or does it extend out from the cell?
Lipid A embedded in outer membrane.
74
Does the core polysaccharide and the O side chain extend out from the cell or is it embedded in the outer membrane?
Core polysaccharide, O side chain extend out from the cell.
75
Which part of the LPS can act as a endotoxin?
Lipid A portion serves as the endotoxin.
76
Why is LPS so important?
* contributes to negative charge on cell surface
* helps stabilize outer membrane structure
* may contribute to attachment to surfaces and biofilm formation
* creates a permeability barrier
* protection from host defenses (O antigen)
* can act as an endotoxin (lipid A)
77
Why is the gram-negative outer membrane more permeable than the plasma membrane?
* Due to presence of porin proteins and transporter proteins.
* porin proteins form channels to let small molecules (600-700 daltons) pass
78
What does a hypotonic environment consist of?
* solute concentration outside the cell is less than inside the cell
* water moves into cell and cell swells
* cell wall protects from lysis
79
What does a hypertonic environment consist of?
* solute concentration outside the cell is greater than inside
* water leaves the cell
* plasmolysis occurs
80
What does penicillin inhibit?
Penicillin inhibits peptidoglycan synthesis.
81
What bond does lysozyme break in the cell wall?
Lysozyme breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid.
82
Which type of organisms that lose a cell wall may survive in isotonic environments?
* protoplasts
* spheroplasts
* mycoplasma
* does not produce a cell wall
* plasma membrane more resistant to osmotic pressure
* because it has cholesterol in its cell membrane, which is normally not characteristic of bacteria
83
Do Archaeal cell walls lack peptidoglycan?
Yes, some have pseudopeptidoglycan, also called pseduomurein.
84
Which components are found outside of the cell wall?
* outermost layer in the cell envelope
* glycocalyx
* capsules and slime layers
* S layers
* aid in attachment to solid surfaces
* e.g., biofilms in plants and animals
85
What are capsules usually composed of?
Polysaccharides
86
True or False:
Capsules are well organized and not easily removed from the cell.
True
87
What are the protective advantages of a capsule?
* resistant to phagocytosis
* protect from desiccation
* exclude viruses and detergents
88
Are capsules visible under the light microscope?
Yes
89
What are the characteristics of slime layers?
* similar to capsules except diffuse, unorganized and easily removed
* slime may aid in motility
90
What are the characteristics of the S layes?
* Regularly structured layers of protein or glycoprotein that self-assemble
* in gram-negative bacteria the S layer adheres to outer membrane
* in gram-positive bacteria it is associated with the peptidoglycan surface
* Protect from ion and pH fluctuations, osmotic stress, enzymes, and predation
* Maintains shape and rigidity
* Promotes adhesion to surfaces
* Protects from host defenses
* Potential use in nanotechnology
* S layer spontaneously associates
91
The biofilm layer, S layer, and slime layers are all important for attachment; so are fimbriae.
Important to Know for the exam.
92
True or False:
The external structures extend beyond the cell envelope in bacteria.
True
93
What do external structures of the bacterial cell function to do?
* Extend beyond the cell envelope in bacteria
* Function in protection, attachment to surfaces, horizontal gene transfer, cell movement
* pili and fimbriae
* flagella
94
What are fimbriae?
* short, thin, hairlike, proteinaceous appendages (up to 1,000/cell)
* can mediate attachment to surfaces
* some (type IV fimbrieae) required for twitching motility or gliding motility that occurs in some bacteria
95
What are sex pili?
* longer, thicker, and less numerous (1-10/cell)
* genes for formation found in plasmids
* required for conjugation (mating)
96
What are flagella?
* threadlike, locomotor appendages extending outward from plasma membrane and cell wall
* Functions:
* motility and swarming behavior
* attachment to surfaces
* may be virulence factors
97
What are the three parts of flagella?
* Filament
* extends from cell surface to the tip
* hollow, rigid cylinder of flagellin protein
* Hook
* links filament to basal body
* Basal Body
* series of rings that drive flagellar motor
98
What are bacterial flagella?
* thin, rigid protein structures that cannot be observed with bright-field microscope unless specially stained
* ultrastructure composed of three parts
* pattern of flagellation varies
99
What are the different patterns of flagella distribution?
* monotrichous - one flagellum
* polar flagellum - flagellum at end of cell
* amphitrichous - one flagellum at each end of cell
* lophotrichous - cluster of flagella at one or both ends
* peritrichous - spread over entire surface of cell
100
What type of directed movement do Bacteria and Archaea have?
* flagellar movement
* spirochete motility
* twitching motility
* gliding motility
101
What is chemotaxis?
* move toward chemical attractants such as nutrients, away from harmful substances
* movement toward a chemical attractant or away from a chemical reprellent
* changing concentrations of chemical attractants and chemical repellents bind chemoreceptors of chemosensing system
* in presence of attractant tumbling frequency is intermeittently reduced and runs in direction of attractant are longer
* behavior of bacterium is altered by temporal concentration of chemical
* chemotaxis away from repellent involves similar but oppostie responses
102
What is flagellar movement good for?
liquids
103
What are gliding and twitching motility good for?
hard surfaces
104
What is spirochete motility good for?
viscous material because it has more of a corkscrew movement
105
What is bacterial flagellar movement?
* Flagellum rotates like a propeller
* very rapid rotation up to 1100 revolutions/sec
* in general, counterclockwise (CCW) rotation causes forward motion (run)
* in general, clockwise rotation (CW) disrupts run causing cell to stop and tumble
106
What does MotA and MotB do in the mechanism of flagellar movement?
MotA and MotB create a channel through which protons can flow. This causes the flagellum to rotate.
107
What is spirochete motility?
* multiple flagella form axial fibril which winds around the cell
* flagella remain in periplasmic space inside outer sheath
* corkscrew shape exhibits flexing and spinning movements
108
What is twitching and gliding motility?
* may involve type IV pili and slime
* twitching
* pili at ends of cell
* short, intermittent, jerky motions
* cells are in contact with each other and surface
* gliding
* smooth movements
109
What is a bacterial endospore?
* complex, dormant structure formed by some bacteria
* various locations within the cell
* resistant to numerous environmental conditions
* heat
* radiation
* chemicals
* desiccation
110
What makes an endospore so resistant?
* calcium (complexed with dipicolinic acid)
* small, acid-soluble, DNA-binding proteins (SASPs)
* dehydrated core
* spre coat and exosporium protect
* DNA repair enzymes
111
