Proteins: Polypeptides | A-level Biology | OCR, AQA, Edexcel

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The key points covered in this video include:
1. Forming Polypeptides
2. Peptide Bonds - Condensation
3. Peptide Bonds - Hydrolysis

Forming Polypeptides

Amino acids are the building blocks of larger proteins - they are monomers. Two amino acids join together to create a dipeptide. Many amino acids join together to create a polypeptide - a protein polymer. A protein is formed when one or many polypeptide chains fold into a specific shape that allows it to perform a specific function.

Peptide Bonds - Condensation

Two amino acids are joined together by a condensation reaction to form a dipeptide. The condensation reaction occurs between the carboxyl group (-COOH) and the amino group (-NH2) on adjacent amino acids. A molecule of water is released as one oxygen and two hydrogen atoms are removed from the amino acids. This creates a peptide bond which joins the two amino acids together to form a dipeptide. A peptide bond is a covalent bond formed when two amino acids are joined together in a condensation reaction. Many amino acids can be joined together in a series of condensation reactions to form a polypeptide. A polypeptide is a polymer made of many amino acids joined together by peptide bonds.

Peptide Bonds - Hydrolysis

A dipeptide can be broken down into two amino acids through a hydrolysis reaction. A hydrolysis reaction requires water as one oxygen and two hydrogen atoms are added to the dipeptide. This breaks the peptide bond, forming two amino acids. Polypeptides can be broken down into amino acids by a series of hydrolysis reactions - this can happen in two ways.

Summary

1. Dipeptides are formed by a condensation reaction between two amino acids
2. Dipeptides are broken down into two amino acids by a hydrolysis reaction
3. Condensation reactions form water and create a peptide bond
4. Hydrolysis reactions require water and break a peptide bond
5. Polypeptides are formed from amino acids by a series of condensation reactions
6. Polypeptides are broken down into amino acids by a series of hydrolysis reactions

Видео Proteins: Polypeptides | A-level Biology | OCR, AQA, Edexcel канала SnapRevise