AMINO ACIDS Flashcards
What are the functional groups of amino acids? (2)
-Carboxylic acids (-COOH_
-Amine group (NH2)
What are the 20 naturally occurring amino acids also known as? (1)
a-amino acids
What does the structure of an amino acid make it? (1)
the structure makes it a chiral molecule, and almost all naturally occurring amino acids exist as the enantiomer
What properties does the carboxylic acid functional group provide the amino acid? (1)
The carboxylic acid group has a tendency to lose a proton (act as an acid)
What properties does the amine group provide the amino acid? (1)
The amine group has a tendency to accept a proton (act as base)
What do amino acids exist as? (1)
Amino acids exist as zwitterions. Ions like these have a both permanent positive charge and a permeant negative charge though the compound is neutral overall.
What are some physical properties of amino acids? (2)
-high melting points
-dissolve well in water but poorly in non-polar solvents
What state are amino acids at room temperature? (1)
A typical amino acids is a white solid at room temperature and behaves very much like an ionic salt.
How do amino acids act in acidic conditions? (1)
In strongly acidic conditions the lone pair of the H2N group accepts a proton to form the positive ion. The amine group has gained a hydrogen ion (its protonated)
How do amino acids act in alkaline conditions? (1)
The OH group loses a proton to form the negative ion. The carboxylic acid group has lost a hydrogen ion (it is deprotonated)
What is the functional group of an amide? (1)
-CONH2
what must an amide functional group react with to create a amide linkage? (1)
The amine group of one amino acid cam react with the carboxylic acid group of another to form an amide linkage.
What is an amide linkage? (1)
-CONH
what is a primary structure of a protein called? (1)
A particular protein will have a fixed sequence of amino acid in its chain.
why are polypeptides classified as condensation polymers? (1)
because a small molecule is eliminated as each link of the chain forms.
How can you break up a protein into its monomers? (1)
Via hydrolysis. When a protein or peptide is boiled with hydrochloric acid of concentration 6 moldm-3 for about 24 hours it breaks down to a mixture of amino acids that make up the original peptide.
Describe wool. (1)
Wool is a protein fibre with a helix which is held together by hydrogen bonds.
what happens when wool is stretched? (1)
When wool is gently stretched the hydrogen bonds stretch and the fibre extends
what happens if wool is replaced in its natural state? (1)
Releasing the tension allows the hydrogen bonds to return to their normal length and the fibre returns to the original shape.
what happens to wool when washed at high temperatures? (1)
washing at high temperatures can permanently break the hydrogen bonds and a garment may permanently lose its shape.
What bonds can form between amino acids? (3)
-hydrogen bonding
-Ionic attractions
-sulfur-sulfur bonds
what is hydrogen bonding? (1)
Hydrogen bonds form between C=O groups and N-H groups
what are ionic attractions? (1)
Ionic attractions between groups on the side chains of amino acids such as -COO- and -NH3
what are sulfur-sulfur bonds? (1)
The amino acids cysteine has a side chain with an -CH2SH group. Under suitable oxidising conditions, two cysteine molecules may react together to form sulfur-sulfur bond that forms a bridge between the two molecules and creates a double amino acid called cystine. Called a sulfur-sulfur bridge
What are the levels of protein structure? (4)
-primary
-secondary
-tertiary
What is the primary structure held together by? (1)
This structure is held together by covalent bonding, therefore it is relatively stable
what is the secondary structure? (1)
a protein chain may form a helix (the a-helix) or a folded sheet (a B-pleated sheet) held in place by hydrogen bonds.
What is the tertiary structure? (1)
The a-helix or B-pleated sheet can itself be folded into a three dimensional shape it is held in shape by a mixture of hydrogen bonding, ionic interactions and sulphur-sulphur bonds
