Session 5-Protein Structure And Function Flashcards
Give examples of biological processes for which proteins are needed
Catalysts (enzymes)
Transporters (eg O2, Fe)
Structural support (eg collagens)
Machines (eg muscular contraction and motion)
Immune protection (eg immunoglobulins)
Ion channels
Receptors (for hormones, neurotransmitters etc)
Ligand in cell signalling (growth factors etc)
What is a peptide bond formation?
The linking of two AA accompanied by the removal of a molecule of water
What is the primary structure of a protein?
Linear AA sequence of the polypeptide chain
What is the secondary structure of a protein?
Folding of AA chain, stabilised by H bonds, alpha helix and beta pleated sheet
What is the tertiary structure of a protein?
Extensive coiling and folding of AA chain with hydrophobic side chain folded inside (3D configuration)
What is the quaternary structure of a protein?
Two or more polypeptide chains to form multi-subunit protein (eg Hb with 4 chains)
True or false: peptide bonds are planar so the alpha C, C, O, N, H all lie in the same plane?
TRUE
True or false: peptide bonds are rigid?
TRUE
What is the isoelectric point (pI) of a protein?
pH at which there is no overall net charge
What is the pI of basic proteins?
> 7
What is the pI of acidic proteins?
<7
What happens if the pH>pI?
Protein is deprotonated
What is the difference between peptides/oligopeptides and polypeptides/proteins?
Peptides/oligopeptides are only a few AA in length whereas polypeptides/proteins are many AA in length
What is a conjugated protein?
A protein that contains covalently linked chemical components in addition to AA
Give two examples of conjugated proteins
Lipoproteins
Glycoproteins
Which small hydrophobic resides are strong alpha helix formers?
Alanine and leucine
Why does proline act as a helix breaker?
The rotation around the N-C bond is impossible
Why does glycine act as a helix breaker?
The tiny R-group supports other conformations
True or false: the alpha helix is a left-handed helix
FALSE - it is right-handed
What is an antiparallel beta sheet?
Adjacent beta strands run in opposite directions with multiple interstrand H bonds stabilising the structure
What are the roles of fibrous proteins? (3)
Support
Shape
Protect
What are the roles of globular proteins? (2)
Catalysis
Regulation
True or false: fibrous proteins consist of a single type of repeating secondary structure
TRUE
Give an example of fibrous proteins
Collagen
Complete the sentence:
Collagen is a ______ helical arrangement of collagen chains
Triple
Which AA is present in this repeating sequence in collagen: AA - X - Y?
Glycine
What is domain in a tertiary structure of a protein?
Part of the polypeptide chain that folds into a distinct shape and often has a specific functional role
Which force is involved in maintaining the primary structure of a protein?
Peptide (covalent)
Which force is involved in maintaining the secondary protein structure?
H-bonds
Which forces are involved in maintaining the tertiary and quaternary protein structures?
Peptide Ionic H-bonds Van der Waals Hydrophobic Disulphide
Between which AAs do disulphide bonds form?
Between cysteine residues
True or false: the interaction between hydrophobic side chains due to the displacement of water is called hydrophobic interaction, not hydrophobic bond
TRUE
Complete the sentence:
A normally folded protein that is functional is said to be in its ______ conformation
Native
The disruption of protein structure is known as?
Denaturation
How does heat cause denaturation?
Increased vibrational energy
How does incorrect pH lead to denaturation?
Alters the ionisation states of AA and changes ionic/H bonds
How do detergents lead to denaturation?
Disrupt hydrophobic interactions
True or false: folding of proteins is random
FALSE - it would take too long if folding was random therefore it is ordered and driven by entropy (in order to find most stable conformation)
How can protein misfolding cause disease?
Altered conformation of normal human protein promotes conversion of existing protein into diseased state
Give examples of diseases caused by protein misfolding
Transmissible spongiform encephalopathies eg BSE, kuru and CJD
