Proteins - levels of structure Flashcards
What are proteins primarily composed of?
One or more chains of amino acids known as polypeptides
What dictates a protein’s structure and function?
The three-dimensional arrangement of polypeptide chains
How many levels of protein structure exist?
Four levels of structure
What is the primary structure of a protein?
The sequence of amino acids bonded by covalent peptide bonds
What determines the primary structure of a protein?
The DNA of a cell
True or False: The primary structure is specific for each protein.
True
What can mutations lead to in terms of protein structure?
The incorrect amino acid being incorporated into the polypeptide chain
What causes the formation of complex shapes within the polypeptide chain?
Secondary structure
What type of bonds primarily form the secondary structure of a protein?
Weak hydrogen bonds
What are the two shapes that can form in secondary structure?
- Alpha-helix (α-helix)
- Beta-pleated sheet (β-pleated sheet)
What does tertiary structure refer to?
How the polypeptide chain folds to form a complex, three-dimensional shape
What interactions contribute to the tertiary structure of proteins?
- Hydrogen bonds
- Hydrophobic interactions
- Covalent bonds
- Ionic bonds
What type of amino acids are less soluble in aqueous solutions?
Non-polar amino acids
Where are proteins composed of non-polar amino acids typically found?
In the centre of a protein
Proteins with polar amino acids are generally found where in the cell?
On the surface of membranes and in a variety of places within the cell
What is quaternary structure in proteins?
The arrangement of multiple polypeptide chains functioning together
What is a subunit in the context of quaternary structure?
Each polypeptide chain in a protein
What is a conjugated protein?
A protein that contains non-polypeptide components (prosthetic groups)
What is haemoglobin’s structure type?
Conjugated protein with quaternary structure
How many subunits does haemoglobin consist of?
Four subunits
What is the structure of collagen?
A fibrous protein consisting of three polypeptide chains wound together in a helix shape
What technique allows imaging of protein structures that are otherwise impossible to observe?
Cryogenic electron microscopy (cryo-EM)
What is the primary process involved in cryo-EM?
Rapid freezing of protein solutions and exposure to electrons
What are the limitations of X-ray crystallography compared to cryo-EM?
- Time-consuming crystallisation
- Only works on single purified proteins
- Some proteins do not crystallise
- Visualization outside cellular environment
