IB DP Biology Proteins Study Notes
IB DP Biology Proteins Study Notes
IB DP Biology Proteins Study Notes at IITian Academy focus on specific topic and type of questions asked in actual exam. Study Notes focus on IB Biology syllabus with guiding questions of
- What is the relationship between amino acid sequence and the diversity in form and function of proteins?
- How are protein molecules affected by their chemical and physical environments?
Standard level and higher level: 4 hours
Additional higher level: 1 hour
B1.2.1—Generalized structure of an amino acid
Key Points:
- Building Blocks of Proteins: Amino acids are the fundamental units of proteins.
- Central Carbon Atom: Each amino acid has a central carbon atom, called the alpha carbon.
- Functional Groups: The alpha carbon is bonded to four different groups:
- An amino group (-NH2)
- A carboxyl group (-COOH)
- A hydrogen atom (H)
- A side chain (R-group)
- Amphiprotic Nature: Amino acids are amphiprotic because the carboxyl group can donate a proton (acting as an acid) and the amino group can accept a proton (acting as a base).
- R-Group Variation: The R-group is the variable part of the amino acid and determines its unique properties and characteristics.
This generalized structure highlights the common features shared by all amino acids, while also emphasizing the diversity introduced by the variable R-group.
B1.2.2—Condensation reactions forming dipeptides and longer chains of amino acids
It explains how amino acids are linked together to form polypeptides (proteins) through condensation reactions.
Key Points:
Peptide Bond Formation:
- A dipeptide is formed when two amino acids join together through a condensation reaction.
- In this reaction, a water molecule is released as the carboxyl group of one amino acid forms a covalent bond with the amino group of another amino acid.
- This covalent bond between the carbon of the carboxyl group and the nitrogen of the amino group is called a peptide bond.
Polypeptide Chains:
- More amino acids can be added to the chain through further condensation reactions, creating longer polypeptides.
- Polypeptides are the main component of proteins.
Ribosomes and Protein Synthesis:
- The formation of peptide bonds is catalyzed by ribosomes within cells.
- The process is directional, with the amino group of a free amino acid always adding to the carboxyl end of the growing polypeptide chain.
Peptide Bond Uniformity:
- The peptide bond itself is the same regardless of the specific R-groups of the amino acids involved, as it always forms between a carboxyl group and an amino group.
This process of linking amino acids together through peptide bonds is fundamental to protein synthesis and the creation of the diverse array of proteins that carry out essential functions in living organisms.
