Amino acids
Describe the categorization of these amino acids, and which amino acids that belong to each group. (at pH 7)
Amino acids are classified using their specific R groups. 1. Nonpolar (hydrophobic) amino acids - have hydrogen, alkyl or aromatic R groups 2. Polar amino acids - have R groups that interact with water, which makes them hydrophilic 3. Polar neutral amino acids - contain a hydroxyl (-OH), a thiol (-SH) or an amide '(-CNH2) R group 4. Polar acidic amino acids - contain a carboxylate (-COO-) R group 5. Polar basic amino acids contain an ammonium (-NH3^+) 3 main types: - Neutral (polar and non-polar) - Acidic - Basic
What reaction describes the reaction in which amino acids are bound together? What is this bound called?
Each amino acid is attached to another amino acid by covalent bond, known as a peptide bond, which is formed by a dehydration reaction. The carboxyl group of one amino acid and the amino group of the incoming amino acid combine, releasing a molecule of water. The resulting is the peptide bond.
What is an "essential" amino acid? Mention 5 of these.
Essential amino acids are those amino acids that must be obtained from the proteins in the diet. Of the 20 available amino acids, 9 are essential. 1. Histidine (His) 2. Isoleucine (Ile) 3. Leucine (Leu) 4. Lysine (Lys) 5. Methionine (Met)
Describe the general structure of a free amino acid.
Every amino acid contains an amine group (-NH2), a carboxyl group (-COOH) and an R group called a side chain, bonded to a central carbon atom. The central carbon is the alpha carbon, it is named so because it is the carbon atom directly adjacent to a carboxyl functional group. Amino acids in proteins are alpha amino acids because the amine group in each is connected to the alpha carbon.
What group on the amino acid give the molecule its characteristics and, when in polymers, the whole protein its shape and function?
Every amino acid has an atom or a R-group. This R-group, or sidechain, gives each amino acid proteins specific characteristics, including size, polarity and pH.
What is a non-essential amino acid? Mention 5 of these.
Non-essential amino acids are those amino acids which can be synthesized in the body. 1. Alanine (Ala) 2. Glycine (Gly) 3. Proline (Pro) 4. Asparagine (Asn) 5. Cysteine (Cys)
Find pI of His. Describe how the structure of the R group of His at pH 7,4 and its properties.
The isoelectric point (pl) for histidine (His) is 7,6. At pH 7,4 the surrounding will be more acidic than Histidine pI.It takes up a hydrogen atom at the R-group. Hydrogen bonded to N-atom. Double bond will break.
A free amino acid can act both as an acid and a base in a solution. How is that? What do you call molecules with this property?
The structure of an amino acid allows it to act as both an acid and a base. An amino acid has this ability because at a certain pH value all the amino acid molecules exist as zwitterions. If acid is added to a solution containing the zwitterion, the carboxylate group captures a hydrogen (H^+) ion, and the amino acid becomes positively charged. If base is added, ion removal of the H^+ ion from the amino group of the zwitterion produces a negatively charged amino acid.
How many amino acids are there?
There are 20 common amino acids.