Protein Structure and Function Flashcards
What type of amino acids are commonly found in beta-turns?
Usually contain small amino acids like glycine and proline
What structural feature do beta-turns connect in a beta-sheet?
Beta-turns connect anti-parallel strands in a beta-sheet
What stabilises a b eta-turn in proteins?
Beta-turns are stabilised by hydrogen bonds between the backbone atoms.
How many amino acid residues make up a beta-turn?
A beta-turn is composed of 4 amino acid residues.
What is the isoelectric point of a protein?
The pH at which the overall charge of the protein is zero.
What is required for a protein to have quaternary structure?
The protein must consist of multiple subunits.
What distinguishes quaternary structure from tertiary structure in proteins?
The quaternary structure involves the assembly of multiple polypeptide subunits, while tertiary structure pertains to the folding of a single polypeptide chain
Do secondary structural elements fold in three dimensions to form the final native protein?
Yes, secondary structural elements fold in three dimensions to result in the final native protein.
Can some proteins contain only alpha-helices and no beta-sheets?
Yes, some proteins are composed entirely of alpha-helices and lack beta-sheets.
Are membrane proteins hydrophobic or hydrophilic on the surfaces in contact with the membrane?
Membrane proteins are hydrophobic on the surfaces in contact with the membrane.
What is the usual composition of the core of a protein?
The core of a protein is usually densely packed, excluding water.
Can some proteins contain only beta-sheets and no alpha-helices?
Yes, some proteins are composed entirely of beta-sheets and lack alpha-helices.
Q
What direction do the R groups of the amino acids in an alpha helix point?
The R groups of the amino acids stick out from the axis of the alpha helix.
What stabilizes the structure of an alpha helix?
The alpha helix is stabilized by hydrogen bonds between the CO and NH groups of the peptide backbone.
Amino acids are chiral. What is chiral?
Four different groups bonded to the tetrahedral a-carbon
Are only L isomers or D isomers found in proteins?
L isomers
What bonds are formed by the oxidation of two cysteines?
Disulphide bonds
What structure is the a-helix?
Tightly-coiled rod-like structure, with R groups sticking out from the axis of the helix
What protein structure refers to:
The spatial arrangement of amino acids that are far apart
The pattern of disulphide bond formation?
Tertiary structure
What does the interior of globular proteins consist of mainly?
Hydrophobic amino acids, very compact
What does the exterior of globular proteins consist of?
Charged and polar amino acids
What protein structure is the amino acid sequence of a protein?
Primary structure
What is the 3D protein structure fromed by hydrogen bonds between peptide NH and CO groups of amino acids?
Secondary structure
