What Are Amino Acids

Amino acid A compound that contains both an amino group and a carboxyl group. 

An a-amino acid, (a) Unionized form and (b) internal salt (zwitterion) form. 

Because they exist as zwitterions, amino acids have many of the properties associated with salts. They are crystalline solids with high melting points and are fairly soluble in water, but insoluble in nonpolar organic solvents such as ether and hydrocarbon solvents. 

The enantiomers of alanine.The vast majority of a-amino acids in the biological world have the L-configuration at the a-carbon. 

All 20 of these protein-derived amino acids are a-amino acids, meaning that the amino group is located on the carbon alpha to the carboxyl group. 

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What are amino acids Draw a general structure for amino acids. 

A fingerprint can often be the most important piece of evidence left behind at the scene of a crime. Police investigators use a variety of methods to visualize fingerprints. One such method involves the use of a chemical agent called ninhydrin, which reacts with the amino acids present in the fingerprint to produce colored compounds that can be seen. But what are amino acids, why are they present in our fingerprints, and what function do amino acids serve ... 

What two amino acids are used to make aspartame ... 

There are a few substances that can reduce serotonin, norepinephrine and/or dopamine rapidly and substantially, reducing them to levels thought to be lower than those of depressed patients.23 That is what reserpine was supposed to do and, as we have seen, it did not cause depression - despite the early clinical impression that it did. Other substances have been used in later studies, the most common of which are amino-acid mixtures that lack the essential amino acids needed by the body to produce these neurotransmitters. For example, having people drink a beverage that is rich in amino acids, but does not contain tryptophan (the amino acid needed to produce serotonin), lowers their serotonin levels within a couple of hours. 

The complete hydrolysis tells us what eight amino acids are in angiotensin II. Reaction with Sanger s reagent indicates that Asp is the N-terminal amino acid. Partial digestion with carboxypeptidase indicates that Phe is the C-terminal amino acid. We can now write the following partial structure ... 

Based on the Rf values and colors of the spots present in your unknown sample compared to those produced by the amino acid standards, what two amino acids are present in your unknown dipeptide Can you now determine the sequence of your unknown dipeptide based on these results and those from Day 2 As before, discuss any uncertainty that may be involved in your identification, as well as how these uncertainties may be eliminated through modifications in the experiment. 

Based on these results, what two amino acids are present in your unknown dipeptide As shown in Table 6-1, it may be difficult to resolve some PTC-amino acids (PTC-arginine and PTC-threonine). Still, this mobile-phase gradient will resolve the majority of the PTC-amino acid derivatives. How might the conditions of this experiment be changed to resolve molecules such as PTC-arginine and PTC-threonine ... 

The liver also plays an essential role in dietary amino acid metabolism. The liver absorbs the majority of amino acids, leaving some in the blood for peripheral tissues. The priority use of amino acids is for protein synthesis rather than catabolism. By what means are amino acids directed to protein synthesis in preference to use as a fuel The K jyj value for the aminoacyl-tRNA synthetases is lower than that of the enzymes taking part in amino acid catabolism. Thus, amino acids are used to synthesize aminoacyl-tRNAs before they are catabolized. When catabolism does take place, the first step is the removal of nitrogen, which is subsequently processed to urea. The liver secretes from 20 to 30 g of urea a day. The a-ketoacids are then used for gluconeogenesis or fatty acid synthesis. Interestingly, the liver cannot remove nitrogen from the branch-chain amino acids (leucine, isoleucine, and valine). Transamination takes place in the muscle. 

However, that does not concern us here. What does, is the fact that there are certain amino acids which remain constant, no matter the source of the enzyme. These are amino acids which are crucial to the enzyme s function and, as such, are often the amino acids which make up the active site. If one of these amino acids should be lost through mutation, the enzyme would become useless and an animal bearing this mutation would have a poor chance of survival. Thus, the mutation would not be preserved. (The only exception to this would be if the mutation either introduced an amino acid which could perform the same task as the original amino acid, or improved substrate binding.)... 

The liver also plays an essential role in dietary amino acid metabolism. The liver absorbs the majority of amino acids, leaving some in the blood for peripheral tissues. The priority use of amino acids is for protein synthesis rather than catabolism. By what means are amino acids directed to protein... 

As shown by the reaction in Equation 7, Factor XIII is a transaminase (transglutaminase) enzyme. Similar enzymes have been isolated from a variety of tissues (64). These enzymes are capable of incorporating a variety of amino compounds into proteins with the addition taking place exclusively at glutamine residues. Therefore, the enzyme appears to have specificity toward glutamine residues of proteins. What other amino acid residues around the glutamine are required is not shown. These transaminases are activated by calcium ion and sulfhydryl compounds. 

First of all, the authors use of isochore GC invokes GC3, the GC level of third codon positions, which is strongly correlated with isochore GC (Bernardi et al., 1985b Bernard and Bernardi, 1986a), R being 0.82 for human genes (Clay et al., 1996). Since what is under consideration here are amino acid composition and hydropathy, the problem must concern primarily the encoded proteins, and therefore the correlation between GC3 and GC1+2 (the average GC levels of first + second codon positions D Onofrio et al., 1991). Incidentally, the correlation between isochore GC and GC1+2 also holds, as expected from the data of Bernardi and Bernardi, 1986a see Fig. 10.8). 

What Are the Acid-Base Properties of Amino Acids ... 

X 10 cm/min results. On the basis of this value, a mean transfer rate of 800 mg per 24 hours may be calculated for these amino acids we measured (glycine, aspartic acid, threonine, serine, glutamic acid, proline, valine, cystine, methionine, isoleucine, leucine, tyrosine, phenylalanine, ornithine, lysine, histidine and arginine). If and to what extent amino acids are absorbed by the... 

Specifically, we may ask the following questions First, what constitutes amino acid incorporation into protein or protein-like material Second, is all incorporation of amino acids into protein-like material due to a de novo formation of peptide bonds Third, what are the factors which influence the apparent rate of incorporation, both in vivo and in vitro systems Fourth, what is the relationship between incorporation of amino acids into total protein-like material and the synthesis of a specific and independent protein molecule and, finally,- what is the nature of the amino acid incorporation in vitro, particularly in the microsomal system, and its relationship to amino acid incorporation in the intact cell ... 

The nonapeptide known as the sleep peptide is hydrolyzed by chymotrypsin to produce Ala-Ser-Gly-Glu and Ala-Arg-Gly-Tyr and Trp. What two amino acid sequences are possible for the sleep peptide ... 

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