Proteins and their Functions Flashcards
Why is the genetic code said to be redundant / degenerate?
One amino acid can be coded for by multiple codons.
Describe the primary structure of a protein.
- Amino acid sequence
- Covalent peptide bonds
- Projecting side chains
Describe the secondary structure of a protein.
- Alpha helices and beta plated sheets
- Local structural conformation
- non-covalent bonds:
•Mainly hydrogen bonds
also:
- Hydrophobic interactions
- Van der Waals interactions
- Ionic interactions
Give an example of the role of non-covalent interactions in secondary protein structure.
Hydrogen bonds stabilise the alpha helix.
Describe the tertiary structure of a protein. Name 5 bonds that contribute to it.
- Three-dimensional conformation
- Proteins fold into lowest energy structure.
- Formed by stabilising forces due to side-chain interactions:
- Hydrogen bonds
- Hydrophobic interactions
- Ionic interactions
- Disulfide bridges.
- Salt bridges
Describe the quarternary structure of a protein.
A complex of more than one polypeptide chain.
What are the two main classes of protein tertiary structure?
Fibrous and globular.
What are the 4 main functions of proteins?
- Binding (e.g. ligands and receptors)
- Catalysis (e.g. enzymes)
- Switching (e.g. signalling pathways)
- Structural (e.g. the cytoskeleton)
Which four processes are involved in the regulation of protein function?
- Synthesis
- Localisation (where)
- Modification (active/inactive?)
- Degradation
What does a centrosome consist of? What is its function?
- Two centrioles.
- Organises microtubules for cell structure and pulling apart chromatids during cell division.
What is a sorting signal?
Amino acid sequences in proteins that direct the proteins to the correct site in the cell.
Where are most proteins modified?
- In the endoplasmic reticulum.
- Further modifications in the golgi apparatus.
What modifications are usually made to proteins?
- Glycosylation
- Disulfide bonds
- Phosphorylation
What is phosphorylation?
The addition of a covalently attached phosphate group to amino acid side chains.
Which protein catalyses phosphorylation reactions?
Kinases
Which protein catalyses dephosphorylation reactions?
Phosphatases
Which two reactions of the tyrosine chains of a tyrosine-kinase receptor follow membrane receptor activation?
Dimerisation and phosphorylation.
Which adaptor protein binds to the phosphorylated tyrosine-kinase receptor in growth factor signalling?
Ras (G-Protein)
What is the unfolded protein response?
- A stress response related to ER stress that is activated in response to accumulation of unfolded proteins in the ER.
- Halts protein translation
- Degrades misfolded proteins
- Increases production of proteins that assist in molecular folding.
- Can lead to cell death.
What does the UPR help prevent?
Protein conformational diseases linked to aggregation.
What is ERAD?
A pathway which targets misfolded proteins of the ER for degradation.
What is cystic fibrosis caused by?
- A mutated CFTR membrane protein.
- Mutated protein incorrectly folded, degraded in ER
- Receptor does not reach the membrane.
