5. Protein structure and sequencing Flashcards
All protein molecules contain what?
Carbon, oxygen, nitrogen and hydrogen.
These elements, sometimes combined also with phosphorus and sulfur, create amino acids; the building blocks of proteins. In other words, proteins are polymers built from monomer units called what?
Amino acids.
The function that a particular protein carries out is dependent on what?
Its shape.
The different structures of a protein can be quite complicated but we can think of them like building a house. As we know, all proteins start with what building blocks?
Amino acids.
If two amino acids join together they form a dipeptide. If three amino acids join together they form a tripeptide. A polymer made from lots of amino acids is called a _______.
A polypeptide.
The most simple form of a protein is what?
The primary structure.
This level of organisation involves the number, type and sequence of amino acids.
How are the amino acids within the primary structure bonded to form a polypeptide chain?
Covalently.
Polypeptide chains have how many distinct ends?
Two.
If we look at the amino acid cysteine, shown in the image to the right, we can see that this molecule has different functional groups on either end. On the left-hand side of the molecule is an amino group (—NH2), also known as an amine group, while on the right-hand side of the molecule is a carboxyl group (—COOH).
When amino acids join together to form a polypeptide it is a peptide link that forms to connect the amino acids. This peptide link is actually which functional group?
An amide functional group (−CONH−).
To form the peptide link the hydroxy group is removed from the carboxyl group, and one hydrogen is removed from the amino group. This allows the carbon atom of the carboxyl group to bond to the _______ of the amino group and thus the peptide link is formed.
Nitrogen atom.
The secondary structure of a protein refers to the what of the polypeptide chain due to the interactions of the polypeptide backbone, namely hydrogen bonding between certain atoms?
Folding.
There are different shapes in which a polypeptide chain can form; common shapes are what?
α-helices and β-pleated sheets.
Hydrogen bonds can form between peptide links due to the polar nature of the -NH group and which group?
-C=O group.
Where these bonds form determines the shape that the chain takes.
α-helices are formed when a segment of the polypeptide chain is pulled into what shape?
A coil structure (like a spring).
Hydrogen bonds form due to the partial positive charge on the hydrogen present in the −NH group of one amino acid and the partial negative charge on the oxygen present in the C=O group of another amino acid.
Much like their name suggests, β-pleated sheets have what structure?
A sheet-like structure.
Instead of hydrogen bonds forming in a way that produces a coil, β-pleated sheets are formed between peptide links on neighbouring sections of polypeptide chains.
What bonding can occur between amino acids in particular positions within the polypeptide chain, resulting in the polypeptide chain twisting and folding into different arrangements, including α-helices and β-pleated sheets?
Hydrogen bonding.
These different arrangements are the secondary structures of proteins.
For some proteins tertiary structure is as far as they will go, but for other proteins there is one final step, called what?
These proteins are called what?
Quaternary structure. These proteins are called oligomers.
The quaternary structure is simply the linking of multiple polypeptide chains in a particular spatial arrangement.
One of the most well-known examples of an oligomer is what?
Haemoglobin.
Haemoglobin is the iron-containing protein present in humans armed with the task of transporting oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs.
What are the 4 types of protein structure?
