B2 Chapter 1: Proteins Flashcards
What are 2 causes of a variation of proteins encoded by a single gene?
- Alternative splicing
- Post-translational modifications
Approximately how many amino acids form a polypeptide?
40 - 5 000
What is the approximate range of relative molecular mass of a polypeptide?
4 000 - 580 000
What is relative molecular mass?
The ratio of the sum of atomic masses within a molecule to the 1/12 the mass of a carbon-12 atom.
Name 10 major groups of proteins.
- Enzymes
- Structural proteins
- Adhesion proteins
- Signalling proteins
- Receptor proteins
- Transport proteins
- Motor proteins
- Immunoglobulins
- Storage proteins
- Gene regulatory proteins
What is the function of adhesion proteins?
To mediate the cell-cell or cell-extracellular matrix contact.
What is the function of signalling proteins?
To faciliate inter- and intracellular communication through being recognised by the relevant receptor molecules.
What is the function of receptor proteins?
To recognise specific signalling molecules in the extracellular or intracellular environment in order to faciliate communication.
Name two types of receptor proteins?
Not specific names, just types.
- Cell surface receptors
- Intracellular receptors
What is the function of transport proteins?
To facilitate transport of substances within, to, and from the cell. E.g., membrane transport proteins
What is the function of motor proteins?
Moving vesicles along mictrotubules to their destination to be released. Faciliates movement.
What is the function of Immunoglobulins?
Also known as antibodies, they recognise specific antigens on the surface of infected cells or foreign bacteria.
What is the function of storage proteins?
To bind to and store nutrients.
What is the function of gene regulatory proteins?
Bind to DNA to regulate gene expression.
What type of protein is ferritin?
Storage protein - specifically iron.
Give one example of a gene regulatory protein.
Lac repressor.
What are ligands?
An ion or molecule that binds to a specific associated protein at its binding site.
What is ‘Primary structure’?
In proteins
The amino acid sequence
What is a proteins secondary structure?
The stable three-dimensional arrangements stretches of a polypeptide makes. (alpha helices and beta sheets)
What is a proteins tertiary structure?
The arrangement of a proteins secondary structures.
What is a proteins Quarternary structure?
The arrangement of subunits of a multimeric protein.
What is the difference between a homomeric protein and a heteromeric protein?
A homomeric protein contains identical subunits.
A heteromeric protein contains different subunits.
If a protein is formed of 4 subunits that are all the same, how could you describe it?
Homotetrameric
What is a cytokine?
A type of signalling protein
What is a cofactor?
A non-protein group that is associated with a protein. Essential for the proteins function.
Give one example of a cofactor.
Haem in haemoglobin
If a protein is formed of only one polypeptide chain, how can it be described?
Monomeric
What is a protein domain?
Dictinct units within a protein that have particular function.
What are disulfide bridges?
Covalent bonds between two cysteine residues.
What is the function of disulfide bridges in a protein?
Stabilises the arrangement of the protein by holding sections together - within a subunit or between subunits.
Are alpha helices right handed or left handed?
Right handed
What are protein folds/motifs?
Extensive arrangements of a proteins secondary structures.
What is a β barrel?
A protein fold/motif in which β sheets wrap around to form a barrel-shaped structure where the inner surface is often hydrophobic.
What can a β barrel be used for?
To carry molecules.
What is a rossman fold/dinucleotide binding fold?
α helices arranged alternately on either side of β sheet
What are the repeating atoms in a polypeptide backbone?
N, C, C with O
What is the proper term for the central carbon atom within an amino acid?
α-carbon/ Cα
In an amino acid what is attached to the α-carbon?
Not including the carboxyl and amino group
A hydogren and the side chain of the amino acid/