A Level Biology Lesson 11:
Proteins: Amino Acid Structure.
Task 1. Check Where this Lesson fits into your Exam Specification!
Task 2. Watch the Revision Notes Lesson in Full.
00:00 Intro Screen / Learning Outcomes
00:57 Proteins are diverse macromolecules.
01:17 All Proteins are polymers composed of smaller monomers known as amino acids.
01:42 Amino Acid Structure
02:31 Amino Acids join together via condensation reactions to form Dipeptides.
03:39 Proteins are made up from Hydrogen, Oxygen and Carbon...
03:58 Glycine (GLY)
04:36 Methionine (MET)
04:56 Polypeptides are many amino acids...
Download, Print out & complete the accompanying Interactive Worksheet.
A-Level Biology "Proteins: Amino Acids - Dipeptides and Polypeptides" Lesson 11. Summary.
Proteins are extremely diverse, Whether the protein is an enzyme, transport protein, antibody… etc. All are polymers made up from Amino Acids.
Amino Acids join together via condensation reactions to form polypeptides.
You have to be able to recognise the structure of an amino acid, be able to label it and show how they join together to form dipeptides, [and therefore, tripeptides and polypeptides].
Here’s is the structure of a typical amino acid:
When amino acids join together via condensation reactions, the NH2 group from one amino acid joins with the COOH group of another. A H2O molecule is released and a Peptide bond linking the amino acids is formed.
Here’s an example of a dipeptide:
Polypeptides range from a few amino acids to thousands in length.
A functional protein maybe just one of these polypeptides (which has folded and coiled – see next lesson), or could be more than one polypeptide associated together to form a functional protein, e.g. collagen and haemoglobin.
Check Your Spec!
★ AQA Specification Reference: - 188.8.131.52 General properties of proteins. Amino acids are the monomers from which proteins are made. The general structure of an amino acid. where NH2 represents an amine group, COOH represents a carboxyl group and R represents a carbon-containing side chain. The twenty amino acids that are common in all organisms differ only in their side group. A condensation reaction between two amino acids forms a peptide bond. Dipeptides are formed by the condensation of two amino acids. Polypeptides are formed by the condensation of many amino acids.
★ CIE Specification Reference: - 2.3 Proteins a) describe the structure of an amino acid and the formation and breakage of a peptide bond.
★ Edexcel (Biology A – Salters-Nuffield) Specification Reference: - Topic 2: Genes and Health 2.9 i) Know the basic structure of an amino acid ii) Understand the formation of polypeptides and proteins (amino acid monomers linked by peptide bonds in condensation reactions).
★ Edexcel (Biology B) Specification Reference: - Topic 1: Biological Molecules 1.3 i) Know the basic structure of an amino acid ii) Understand the formation of polypeptides and proteins (amino acid monomers linked by peptide bonds in condensation reactions).
★ OCR (Biology A) Specification Reference: - 2.1.2 Biological molecules (k) the general structure of an amino acid (l) the synthesis and breakdown of dipeptides and polypeptides, by the formation and breakage of peptide bonds.
★ OCR (Biology B) Specification Reference: - 2.1.3 Proteins and enzymes (a) (i) the basic structure of an amino acid and the formation of peptide bonds.
★ WJEC Specification Reference: - 1. Basic Biochemistry and Cell Organisation (h) the structure and role of amino acids and proteins.
Remember Specifications are often very vague - No matter which exam board you are studying you need to know this.