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Microbiology Exam 2 UTA | Questions And Answers Latest {} A+ Graded | 100% Verified
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Microbiology Exam 2 UTA | Questions And Answers Latest {} A+ Graded | 100% Verified
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Microbiology Exam 2 UTA | Questions And Answers Latest {2024- 2025} A+ Graded |100% Verified
Uniporters - Transport in one direction across the membrane
Symporters - Functions as co-transporters; the two molecules travel in the same direction; 1. Energy is
released as one substituent moves down its concentration gradient 2. This energy moves a second
substrate against its gradient into the cell
Anitporters - Transport a molecule across the membrane while simultaneously transporting another
molecule in the opposite direction; the actively transported molecule moves in the direction opposite to
the driving ion; 1. Antiporter binds substrate A on the cytoplasmic side of the membrane 2.Antiporter
opens to the outside, where the concentration of A is less 3. Substrate A leaves its binding site, and
substrate B then binds to its site 4. Antiporter opens to the inside of the cell. Substrate B is released in
exchange for substrate A
The Phosphotransferase System in E.coli - -Type of group translocation
-Best studied system
-Moves glucose, fructose, and mannose
-Five proteins required
-Energy derived from phosphoenolpyruvate (PEP)
-The product Glucose 6-P is used in glycolysis
Group Translocation - Substance transported is chemically modified during transport across the
membrane, usually phosphorylated
ABC Systems - -ATP-Binding Cassette systems
- >200 different systems identified in prokaryotes
-Often involved in uptake of organic compounds (e.g. sugars, amino acids), inorganic nutrients (e.g
sulfate, phosphate), and trace metals
-Typically display high substrate specificity
,-Contain periplasmic binding proteins
3 components: Periplasmic binding proteins, Membrane- spanning transporter, and ATP-hydrolyzing
protein (i.e ATPase); also requires ATP energy
Shown in diagram at C
Cell Wall - How prokaryotes protect the cell membrane? For most species, the cell envelope includes at
least one structural supporting layer and the most common structural support is _______?
This confers shape and rigidity to the cell and helps it withstand turgor pressure, can see it for example
in E.coli
Mycoplasmas - An example of a few prokaryotes who have a cell membrane with no outer layers
It's difficult to Gram stain
Sacculus - The bacterial cell wall, or this, consists of a single- interlinked molecule; for example
disaccharide or peptidoglycan
Needed to maintain high pressure and solubility in order to maintain its shape
Gram- Negative - Has thin peptidoglycan (PG)
Gram- Positive - Has thick peptidoglycan (PG)
Peptidoglycan or Murein - Most bacterial cell walls are made up of this [only in bacteria]
The molecule consists of:
,-Long polymers of two disaccharides called: N-acetylglucosamine (NAG or G) and N-actelymuramic acid
(NAM or M)
-The peptides can form cross-bridges connecting the parallel glycan strands
-Can have Lysine (Gram -) or Diaminopimetic acids (Gram +) amino acids
-Cross-linked differently in G+ and G- bacteria
-5 more Glycine in G+
-Peptide bonds are covalent; more peptide bonds in G+
-No inter bridge between G and G
Beta (1,4) Glycosidic Bonds - The bonds within peptidoglycan between NAG and NAM
Peptidoglycan Is Unique to Bacteria - -Thus the enzymes responsible to its biosynthesis make excellent
targets for antibiotic
-Penicillin inhibits the transpeptidase that cross-links the peptides
-Vancomycin prevents cross-bridge formation by binding to the terminal Ala-Ala dipeptide
-Unfortunately, the widespread use of such antibiotics selects for evolution of resistant strains
Dispersed Zonal Peptidoglycan Growth - Wall synthesis direction in bacilli ex: E.coli (pulse label, 5%
doubling time)
Usually growth from the center
Septal Zonal Peptidoglycan Growth - Ex. cocci (staphylococcus, streptococcus)
Usually growth from the center
Polar Peptidoglycan Growth - Growth in one direction
Ex. actinomycetes, rhizobiales
, Cell Envelope of Bacteria - Most bacteria have additional envelope layers that provide structural support
and protection
Envelope composition defines:
1) Gram positive bacteria (thick PG)- Example: the phylum Firmicutes
2) Gram negative bacteria (thin PG)- Example: the phylum Proteobacteria
3) Mycobacteria- complex, multilayered cell wall; Example: the phylum Actinomycetes
S-Layer - Found in some G+ and most archaea
1st found in archaea- An additional protective layer commonly found in free-living bacteria (usually G+)
and archaea.
-Crystalline layer of thick subunits consisting of protein or glycoprotein
-May contribute to cell shape and help protect the cell from osmotic stress
-Ex. Lysinibacillus
-Ex. in Archaea shows hexagonal symmetry
Gram Positive Cell Walls - -Can contain up to 90% peptidoglycan
-Common to have teichoic acid (acidic substances) embedded in the cell wall
Teichoic Acid - a phosphorylated poly alcohol found in G+ cell wall
Lipoteichoic Acid - Teichoic acid covalently bound to membrane lipids in G+ cell walls
Capsule - -Made of polysaccharide (Exopolysaccharide/ EPS) and glycoprotein
-Protects cells from phagocytosis
-Found in G+ and G- cell walls but the structure is different
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