GCE AQA BIOL - Proteins
Unit 3.1 Biology and disease
3.1.2 The digestive system provides an interface with the environment. Digestion involves enzymic hydrolysis producing smaller molecules that can be absorbed and assimilated.
Proteins are a class of biological molecules.
Along with carbohydrates and fats, they are one of the three main macromolecule nutrients that humans consume.
Functions of proteinsFor GCE AQA Biology, you should know that proteins have many possible functions in all living organisms. Proteins can be divided into 2 types:
Globular proteins: metabolic functions
The structure of proteinsThe building blocks (‘monomers’) of proteins are individual amino acids. In GCE AQA Biology, you will be asked to identify the general structure of an amino acid as:
Formation of proteins
Amino acids are joined together in long chains, forming a polypeptide, which is eventually coiled into a protein.
Protein structureThe structure of a protein can be divided up into 4 main parts: primary, secondary, tertiary, and quaternary.
Primary structure: the sequence of amino acids
Secondary structure: alpha-helices formed by hydrogen bonds
Tertiary structure: the 3D shape of the protein
Quaternary structure: when more than one polypeptide chain are linked, and/or when prosthetic groups are added
Test for proteinThe test for proteins is known as a Biuret test. It tests for the characteristic peptide bond of proteins.
Procedure for GCE AQA Biology:
Positive result (peptide bonds are present, so protein is likely present): Purple colourNegative result (no peptide bonds present, no protein): Remains blue in colour
That's all for today!
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Written by Justine | Biology Specialist @ Tuttee
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