Other
MICROBIOLOGY EXAM 2 UTA
- Course
- Institution
MICROBIOLOGY EXAM 2 UTA
[Show more]
Content preview
MICROBIOLOGY EXAM 2 UTAUniporters
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
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller GEEKA. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $13.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
79271 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now