1.6 Proteins Flashcards
Describe the structure of an amino acid (like the groups in the amino acid)
*Amine group (NH2) on the left
* Carboxyl group on the right (C=OOH)
* R group/ variable group at the top
and a C and a H below the carbon
Describe how amino acids are joined together to form a dipeptide
- Condensation reaction
- Water is removed
- Peptide bond forms between OH of carboxyl and H of the Amine group
What are proteins
Polymer made up of the monomer amino acids
What is the primary structure is
The sequence of amino acids in a polypeptide chain joined by peptide bonds
What is the secondary structure
- Folding (repeating patterns) of polypeptide chains e.g. alpha helix or beta pleated sheets
- Due to hydrogen bonds between amino acids
- between the NH and C=O
What is the tertiary structure
● 3D folding of polypeptide chain
● Due to interactions between amino acid R groups
(dependent on sequence of amino acids)
● Forming hydrogen bonds, ionic bonds and disulfide bridges
Where do the ionic and Disuphide bonds form in the tertiary structure
Between the R groups of different amino acids
Describe the quaternary structure of a protein
- More than one polypeptide chain
- Formed by interactions between polypeptides (hydrogen bonds ionic bonds and disulfide bridges)
What is an example of a quarternary structure protein
Haemoglobin
What happens if a protein denatures
The bonds which hold the tertiary structure and secondary structure break and therefore their unique shape is lost
What is the importance of the primary structure
If even one amino acid in the sequence changes it will cause the Ionic, Hydrogen or disulphide bond to form at a diff location resulting in a diff 3D shape
EXPLAIN HOW A CHANGE IN DNA BASE SEQUENCE CAN AFFECT AN ENZYME REACTION
Base sequence determines sequence of amino acids in polypeptide chain/primary structure
3 bases code for one amino acid
Primary structure determines position of bonds between R groups in the tertiary structure
Hydrogen, ionic bonds and disulphide bonds
A change in tertiary structure/ bonds changes shape of active site of the enzyme
Meaning the substrate can no longer bind to form an enzyme substrate complex
How many amino acids are common in all organisms? How do they vary?
The 20 amino acids that are common in all organisms differ only in their side group (R)
What are dipeptides and polypeptides?
● Dipeptide - 2 amino acids joined together
● Polypeptide - many amino acids joined together
Describe the test for proteins
- Add biuret reagent (sodium hydroxide + copper (II) sulphate)
- Positive result = purple / lilac colour (indicating presence of peptide bonds)
What are the two types of proteins and give examples
Fibrous-Have structural functions such as collagen
Globular- Carry out metabplic functions such as enzymes and haemoglobin
