Tutor profile: Wylan W.
Compare and contrast strong acid and weak acid. Give one example each.
The ions of both strong acids and weak acids dissociate when dissolved in water, releasing hydrogen ions (protons) and lowers the solution pH. However, the ions of strong acids dissociate (almost) completely; while weak acids dissociate partially. The extent of proton dissociation in a given acid is defined as pKa, it is based on the solution pH and the Gibbs free energy change from the dissociation reaction. This relationship is described by the Henderson-Hasselbalch equation.
What is the relative chirality of amino acids incorporated in proteins in most known species, including all known eukaryotes? Why is one chirality favoured by natural selection over the other?
L-amino acids are incorporated in proteins most biological contexts with few bacterial exceptions. The current consensus is that neither chirality is inherently favoured by natural selection, but only using amino acids of one chirality means cells only require one set of enzymes to process each amino acid instead of two. L-amino acids might have been favoured due to stochastic events, or currently unclear evolutionary advantages.
Is DNA replication conservative, semi-conservative, or dispersive? Explain your chosen answer and describe the supporting evidence.
DNA replication is described as semi-conservative, meaning each mother DNA strand is separately incorporated into one of the two daughter DNA sequences. The Meselson-Stahl experiment proved this concept using isotopic labelling of nitrogen (constituting DNA bases) and tracked the destination of each nucleotide in the resulting daughter DNA by centrifugation in a salt gradient.
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