At sea level, a normal blood oxygen level (saturation) is usually 96 - 97%. Although there are no generally accepted classifications for severity of oxygen desaturation, reductions to not less than 90% usually are considered mild.Dips into the 80 - 89% range can be considered moderate, and those below 80% are severe.t sea level, a normal blood oxygen level (saturation) is usually 96 - 97%. Although there are no generally accepted classifications for severity of oxygen desaturation, reductions to not less than 90% usually are considered mild.
Because all amino acids contain amine and carboxylic acid functional groups, they share amphiprotic properties. Below pH 2.2, the predominant form will have a neutral carboxylic acid group and a positive Î±-ammonium ion (net charge +1), and above pH 9.4, a negative carboxylate and neutral Î±-amino group (net charge â1).
Polar Amino Acids. Six amino acids have side chains that are polar but not charged. These are serine (Ser), threonine (Thr), cysteine (Cys), asparagine (Asn), glutamine (Gln), and tyrosine (Tyr). These amino acids are usually found at the surface of proteins, as discussed in the Proteins 2 module.