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Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of nosocomial or hospital infections. What are the consequences of drug resistance in the prevention of MRSA infection?
Bactericidal drugs often work by disrupting the synthesis of molecules and macromolecules that are specific to bacteria and not found in their eukaryotic hosts. In this way, they inhibit bacterial biochemical processes without interfering with the physiology of the host. Drug resistance arises when genetic mutations that block the drug’s interaction with bacterial processes arise and are selected for. The block may be at the level of enzyme activity or the bacterium may acquire novel ways of pumping the drug out of the cell or of inactivating it. Drug-resistant mutations frequently become widespread through horizontal gene transfer.
The permeability of a protein-free lipid bilayer to various molecules depends on their properties. Sort the following in order of low to high permeability from left to right. • O2 • ATP • RNA oligonucleotide • Na+ • Glucose • Urea explain the rationale.
324561 most of the lipid bilayer is hydrophobic (tail) so small and uncharged molecules are preferred. RNA is largest, then ATP. Charged molecule Na+ is unfavored so it goes next. this is filled by glucose, urea and oxygen in decreasing sizes
Neuromuscular transmission involves the sequential activation of several ion channels. How would you order the sequence of actions A through E to correctly lead to muscle contraction? A. Opening of voltage-gated Na+ channels in the muscle cell plasma membrane B. Opening of Ca2+ release channels in the sarcoplasmic reticulum membrane C. Opening of ionotropic acetylcholine receptors on the muscle cell plasma membrane D. Opening of voltage-gated Ca2+ channels in the T tubules E. Opening of voltage-gated Ca2+ channels in the motor neuron
ECADB Ca2+ channels open and allow Ca2+ to enter the synapse influx of Ca2+ allow vesicles containing acetylcholine to release into the synaptic cleft the initial depolarisation causes Na+ channels to open which amplifies the signal action potential travels along the neuronal and reaches the end of T tubules Ca2+ is then released into the sarcoplasmic reticulum membrane which directly causes muscles to contract
Briefly discuss biological polymerisation with reference to DNA, RNA and protein.
driven by ATP hydrolysis usually a condensation reaction - water molecule is produced as a side product cells usually couple energetically favourable reactions which release energy and produce heat to energetically unfavourable reactions for example breaking ATP into ADP and Pi is exothermic, which facilitates the endothermic reaction of polymerisation of forming peptide bonds between amino acids
Imagine that the genetic code is a double or triplet code; it uses two/three nucleotides to specify each amino acid. In this code, the amino acid specified by each codon depends only on the composition of the codon; not the sequence. Would you expect the genetic codes to lead to difficulties in the process of translation, using mechanisms analogous to those used in translating the standard genetic code? Give an example.
relatively easy to see how a doublet code could be translated by a mechanism similar to that used with the standard genetic code (because doublet anticodons are invertible) but more difficult to see how the composition of a stretch of 3 nucleotides could be translated without regard to the order of nucleotides, because base-pairing could no longer be used. An AUG, for example, would not base-pair with the same anticodon as a UGA.