Proteins Flashcards
How do proteins differ from carbohydrates and lipids in organisms? (amount + differentiation)
Whilst carbohydrates and lipids are relatively few and similar across organisms, proteins are numerous and vary between species
What makes each type of protein molecule different?
The shape of each protein molecule is different from all other types, allowing them to perform specific functions
What are the monomer that make up polypeptides?
Amino acids
What do polypeptides combine to form?
Proteins
How does the universal use of 20 amino acids provide evidence for evolution?
The fact that the same 20 amino acids occur in all living organisms suggest common ancestry, providing indirect evidence for evolution
What are the four chemical groups attached to the central carbon atom in an amino acid?
- Amino group (NH3)
- Carboxyl group (COOH)
- Hydrogen atom (H)
- R (side) group
What determines the differences between the 20 naturally occurring amino acids?
The R (side) group, which varies between each amino acid
What type of reaction forms a peptide bond between two amino acids?
Outline the full process of forming a peptide bond
> What is removed during the formation of a peptide bond
> What groups combine to form a peptide bond?
A condensation reaction occurs between two amino acids to form a dipeptide. The -OH from the carboxyl group of one amino acid and the -H from the amino group of another come together form the peptide bond, with the removal of a water molecule.
What is a dipeptide?
A molecule formed when two amino acids join together by a peptide bond
How can a peptide bond be broken?
By hydrolysis, which involves the addition of a water molecule
What is polymerisation in the context of proteins?
The process in which many amino acid monomers join together through condensation reactions to form a polypeptide
What is the primary structure of a protein, and what determines the primary structure?
The specific sequence of amino acids in a polypeptide chain, which is determined by the DNA
How does the primary structure of a protein determine its function?
The sequence of amino acids dictates the protein’s shape, which is essential for its specific function
What happens if a single amino acid in the primary structure is changed?
It may alter the protein’s shape, affecting or preventing it’s ability to function
What is the secondary structure of a protein, and what is the main bond responsible for the secondary structure of proteins?
This is the structure that forms when weak hydrogen bonds form between the primary structures, causing the chain to twist into a 3D shape (like a helixes or beta pleated sheets)
What groups in a polypeptide chain are involved in forming the secondary structure of a protein?
The -NH and -C=O groups on either side of every peptide bond
Why do hydrogen bonds form in the secondary structure of proteins?
The hydrogen in the -NH group has a slight positive charge, whilst the oxygen in the -C=O group has a slight negative charge, allowing them to attract and form hydrogen bonds
What is a - helix?
A coiled structure formed due to hydrogen in the secondary structure of proteins
How does a B pleated sheet form?
Polypeptide chains run alongside each other, forming a sheet - like structure stabilised by the hydrogen bonds
What is the main difference between a a-helix and a B pleated sheet?
An a - helix is a coiled structure, while a B pleated sheet consists of polypeptide chains lying parallel or antiparallel in a folded, sheet - like arrangement
