4.7 Amino acids, peptides and proteins Flashcards
(11 cards)
What is the structure of an amino acid?
AN amino acid has a NH2 group attached to a carbon that is attached to a COOH. This carbon atom is called the alpha carbon atom.
What do all amino acids contain?
Apart from aminoethanoic acid, all amino acids contain a chiral centre(s)
Why are the melting points of amino acids much higher than expected? and explain
because they can act as zwitterions meaning the carboxylic acid group looses a proton (H+), becoming COO- and the H+ goes to the NH2 group making it +NH3
This is possible due to the lone pair of electrons on the nitrogen atom.
therefor amino acids can from strong ionic bonds between the negative and positive ions either side of the alpha carbon.
They are still considered neutral acids as the + and - cancel eachother out.
What is an amphoteric compound?
An amphoteric compound is one that can react as both a base and an acid. Due to their zwitterionic nature, α-amino acids are able to do this.
When α-amino acids are dissolved in an acidic solution, they gain a proton, and if dissolved in a basic solution, they lose a proton.
How is a peptide bond formed?
Two amino acid molecules can join in a condensation reaction to form a dipeptide. A condensation reaction is a reaction in which two molecules are joined to form one molecule. A smaller molecule is lost in the reaction, often water.
The two amino acid molecules can either be the same or different. The bond is called a peptide bond.
Two of the same amino acids can only form one dipeptide, but if two different amino acids are joined, they can form two different dipeptides, depending on where the peptide bond is formed.
What happens when two peptides bond?
When two or more peptides are joined, they form a polypeptide. These, in turn, can form proteins.
What are the three structures of proteins?
Primary
The sequence of amino acids that make up the protein chain.
Secondary
How parts of the protein can fold up to form an α-helix that is held in place by hydrogen bonds or a β-pleated sheet. In the β-pleated sheets, amino acids form a shape like a piece of paper stabilized by hydrogen bonds between amino acids in different polypeptide chains.
Tertiary
This refers to the protein as a whole and the way the α-helices or β-pleated sheets of the protein fold with respect to each other.
Why are proteins important?
Proteins are an essential component of a healthy diet. In the body they are used for growth and repair.
They also serve many structural functions, e.g. in nails, feathers, skin and the collagen of cartilage.
Some proteins are enzymes which function as biological catalysts.
Others act as hormones; an example is insulin which helps to regulate glucose levels.
what does a peptide bond/dipeptide linkage/amide linkage look like?
What are essential amino acids?
essential amino acids are those alpha-amino acids that cannot be synthesised in the body and must be supplied through diet.
