3.6 Protein Structure Flashcards
What’s the structure of proteins
Peptides are polymers made up of amino acid molecules.
Proteins consist of one or more polypeptides arranged as complex macromolecules and have specific functions.
Contains C, H, O & N.
How are amino acids formed? How many are there?
Different R-groups result in different amino acids.
20 different amino acids are found in cells. 5 are non-essential. 9 are essential can can only be obtained from what we eat. 6 are conditionally essential as they are needed for growing children.
How do you synthesise proteins?
Amino acids join when the amine group and carboxylic acid groups connected to the central carbon atoms react.
The R-groups are not involved at this point.
The hydroxyl in the carboxylic acid group of one amino acid reacts with a hydrogen in the amine group of another amino acid.
A peptide bond is formed between the amino acids and water is produced (e.g. of condensation reaction).
Resulting compound is a DIPEPTIDE.
When many amino acids are joined together by peptide bond, a polypeptide is formed. This reaction is catalysed by the enzyme peptidyl transferase present in ribosomes, the sites of protein synthesis.
The different R-groups of the AA’S making up a protein are able to interact with each other, forming different types of bonds, These bonds lead to the long chains of amino acids (polypeptides) folding into complex structures (proteins).
What’s the primary structure of proteins
Sequence in which the amino acids are joined; directed by info carried within DNA.
The particular amino acids in the sequence will influence how the polypeptide folds give the protein’s final shape.
The only bonds involved in primary structure are peptide bonds.
What’s the secondary structure of proteins?
The O, H, N atoms of the basic, repeating structure of the amino acids interact. Hydrogen bonds may form within the amino acid chain, pulling it into a coil shape called an alpha helix.
Another way of forming the secondary structure is:
Polypeptide chains can lie parallel to one another joined by hydrogen bonds, forming sheet-like structure. This pattern causes the structure to look pleated, hence the name beta pleated sheet.
Secondary structure is the result of hydrogen bonds causing twists and folds and forms at regions along long protein molecules depending on the amino acid.
What’s the tertiary structure of proteins?
The folding of a protein into its final shape. Often includes sections of secondary structure.
The coiling/folding of sections of proteins into their secondary structures brings R-groups of amino acids closer so they can interact; further folding will occur.
These interactions occur between R-groups:
- hydrophobic/hydrophilic
- hydrogen bonds
- ionic bonds
- disulfide bonds
This produces a variety of differently shaped proteins with specialised characteristics and functions.
Affects the final function of the protein.
What’s the quaternary structure of proteins?
this results from the association of 2 or more individual proteins called subunits.
The interactions between the subunits are the same as in the tertiary except they are between different proteins rather than within one molecule.
The protein subunits can be identical or different.
Enzymes often consist of 2 identical subunits whereas insulin has 2 different subunits.
Overall, the tertiary structure is how the individual subunits are arranged.
How do you breakdown peptides
Proteases are enzymes that catalyse the reverse reaction and turn peptides back into amino acids.
Peptides are created by amino acids linking together in condensation reactions to form peptide bonds.
What are prosthetic groups and what do they do?
Some proteins contain other non-protein molecules forming part of the structure.
Help protein carry out its role.
Haemoglobin has the prosthetic group haem which binds to oxygen.
Proteins with a prosthetic group are called CONJUGATED PROTEINS.
These are show in the quaternary structure.
