Protein Structure and Function

Question 1

What type of amino acids are commonly found in beta-turns?

Answer 1

Usually contain small amino acids like glycine and proline

Question 2

What structural feature do beta-turns connect in a beta-sheet?

Answer 2

Beta-turns connect anti-parallel strands in a beta-sheet

Question 3

What stabilises a b eta-turn in proteins?

Answer 3

Beta-turns are stabilised by hydrogen bonds between the backbone atoms.

Question 4

How many amino acid residues make up a beta-turn?

Answer 4

A beta-turn is composed of 4 amino acid residues.

Question 5

What is the isoelectric point of a protein?

Answer 5

The pH at which the overall charge of the protein is zero.

Question 6

What is required for a protein to have quaternary structure?

Answer 6

The protein must consist of multiple subunits.

Question 7

What distinguishes quaternary structure from tertiary structure in proteins?

Answer 7

The quaternary structure involves the assembly of multiple polypeptide subunits, while tertiary structure pertains to the folding of a single polypeptide chain

Question 8

Do secondary structural elements fold in three dimensions to form the final native protein?

Answer 8

Yes, secondary structural elements fold in three dimensions to result in the final native protein.

Question 9

Can some proteins contain only alpha-helices and no beta-sheets?

Answer 9

Yes, some proteins are composed entirely of alpha-helices and lack beta-sheets.

Question 10

Are membrane proteins hydrophobic or hydrophilic on the surfaces in contact with the membrane?

Answer 10

Membrane proteins are hydrophobic on the surfaces in contact with the membrane.

Question 11

What is the usual composition of the core of a protein?

Answer 11

The core of a protein is usually densely packed, excluding water.

Question 12

Can some proteins contain only beta-sheets and no alpha-helices?

Answer 12

Yes, some proteins are composed entirely of beta-sheets and lack alpha-helices.

Question 13

Q
What direction do the R groups of the amino acids in an alpha helix point?

Answer 13

The R groups of the amino acids stick out from the axis of the alpha helix.

Question 14

What stabilizes the structure of an alpha helix?

Answer 14

The alpha helix is stabilized by hydrogen bonds between the CO and NH groups of the peptide backbone.

Question 15

Amino acids are chiral. What is chiral?

Answer 15

Four different groups bonded to the tetrahedral a-carbon

Question 16

Are only L isomers or D isomers found in proteins?

Answer 16

L isomers

Question 17

What bonds are formed by the oxidation of two cysteines?

Answer 17

Disulphide bonds

Question 18

What structure is the a-helix?

Answer 18

Tightly-coiled rod-like structure, with R groups sticking out from the axis of the helix

Question 19

What protein structure refers to:
The spatial arrangement of amino acids that are far apart
The pattern of disulphide bond formation?

Answer 19

Tertiary structure

Question 20

What does the interior of globular proteins consist of mainly?

Answer 20

Hydrophobic amino acids, very compact

Question 21

What does the exterior of globular proteins consist of?

Answer 21

Charged and polar amino acids

Question 22

What protein structure is the amino acid sequence of a protein?

Answer 22

Primary structure

Question 23

What is the 3D protein structure fromed by hydrogen bonds between peptide NH and CO groups of amino acids?

Answer 23

Secondary structure