3. 1. 4. 1 Properties of Proteins Flashcards
What are amino acids?
Amino acids are the monomers from which proteins are made.
What are the different groups in the genrral structure of an amino acid?
- Amine group (NH2) basic
- Carboxyl group (COOH) acidic
- Side chain (R)
- Hydrogen atom
What do the 20 amino acids that are common in all organisms differ by?
Their side group
What does a condensation reaction between two amino acids form?
A peptide bond
How is a dipeptide formed?
By the condensation of two amino acids. The two amino acids become linked by a new peptide bond between the carbon atom of one amino acid and the nitrogen atom of the other.
How are polypeptides formed
By the condensation of many amino acids
What may a functional protein contain?
One or more polypeptide
What is the role of ionic bonds in the structure of proteins?
Tertiary structure: More bonds form between different parts of the polypeptide chain, including hydrogen and ionic bonds in the further coiling or folding of the chain.
What is the role of disulfide bridges in the structure of proteins?
Disulfide bridges form whenever two molecules of the amino acids cysteine come close together - the sulfur atom in one cysteine bonds to the sulfur atom in the other.
What is the primary structure of a protein?
Chain of amino acids joined by polymerisation. Lots of condensation reactions and peptide bonds. Known as polypeptide chain.
What does the primary structure determine?
Determines properties of protein through type and sequence of amino acids. Controlled by DNA (protein synthesis).
What is the secondary structure of a protein?
Secondary structure: Hydrogen bonds form between the amino acids in the polypeptide chain, causing it to be twisted into a 3D shape such as a coil (alpha helix) or fold (beta pleated sheet).
What is the tertiary structure of a protein?
Further bending or folding of secondary structure forming a 3D globular shape - shape is precise and specific to the function fo the polypeptide.
What is the quaternary structure of a protein?
Folding together more than one polypeptide chain.
What does the ‘R’ group of an amino acid determine?
How it bends and what bonds are formed. There are 3 types of side chain interactions:
- Hydrogen bonds
- Disulfide bonds
- Ionic bonds
Describe the biuret test for proteins.
1) Add food sample to test tube.
2) Add 2ml NaOH and 5-6 drops of CuSO4 solution.
3) Shake gently
4) Allow mixture to stand for 4-5 minutes.
5) Bluiesh/violet colour indicates presence of protien.
What are the 4 different types of amino acids?
- Nonpolar (hydrophobic) with hydrocarbon side chains
- Polar (hydrophilic) with polar or ionic side chains
- Acidic (hydrophilic) with acidic side chains
- Basic (hydrophilic) with NH2 side chains
Describe the structure of an amino acid.
Amino acids are the basic monomer units which combine to make up a polymer called polypeptide.
Polypeptides can be combined to form proteins.
What bonds are involved in the tertiary structure of proteins?
- Disulfide bridges which are fairly strong
- Ionic bonds which form between any carboxylate and amino group not involved in forming peptide bonds these are weaker than disulfide bridges.
- Hydrogen bonds, lots but easily broken
