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2.3.a Describe the structure of an amino acid and the formation and breakage of a peptide bond.
AMINO ACID STRUCTURE
- Amino acids are compounds that have the following general structure:
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/2451083/850587_191771.png)
This image shows the general structure of an amino acid.
- Each carbon atom is bonded to an -NH2 group (amine), a -COOH group (carboxylic acid), and a hydrogen.
- There are 20 amino acids, that differ from each other based on which R group is present:
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/2451083/185552_555211.png)
This image shows the 20 amino acids and their structures! You do not need to memorise this!
PEPTIDE BOND FORMATION AND BREAKAGE
- Peptide bonds are the link formed between the two amino acids.
- When two amino acids are aligned next to each other, one loses a hydroxyl (–OH) group from its -COOH group, and the other loses a hydrogen atom from its -NH2 group.
- This leave a carbon to bond with the nitrogen.
- The formation of this bond occurs via condensation, in a reaction similar to triglyceride synthesis during glycosidic bond formation.
- On the other hand, hydrolysis (i.e., addition of water) breaks peptide bonds and proteins break down into amino acids.
![The formation and breakage of peptide bonds to form dipeptides, via condensation and hydrolysis. The formation and breakage of peptide bonds to form dipeptides, via condensation and hydrolysis.](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/2451083/25213_382247.png)
This image shows the formation and breakage of peptide bonds to form dipeptides, via condensation and hydrolysis.
- Two amino acids linked together are called a “dipeptide”.
- Many amino acids linked together are called a “polypeptide”.
- Proteins are made up of one or many polypeptide chains.
Great job! See you soon! 🤓
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_60/2451083/422034_696197.gif)
References:
Jones, M., & Parkin, M. (2018). Cambridge International AS and A Level Biology. Cambridge: Cambridge University Press.