Proteins

Question 1

State the 9 different functional roles of proteins:

Answer 1

1)Structural 2)Enzymatic 3) Transport 4) Signalilng 5) Environmental sensing 6) Defensive proteins 7) Hormonal and regulatory proteins. 8) Storage proteins 9) Genetic regulatory proteins

Question 2

What are proteins?

Answer 2

Polymers (polypeptides) of amino acids linked by peptide bonds

Question 3

What is a peptide bond?

Answer 3

Is the result of a condensation reactions between the carboxyl group of one amino acid and the amino group of another amino acid.

Question 4

What are the two characteristics of the peptide bonds that affect the structure of the protein?

Answer 4

1) In the C-N linkage the adjacent alpha carbon are not free to rotate fully 2) The oxygen bound to the carbon (C=O) is slightly negatively charge whereas the hydrogen bound to the nitrogen (N-H) is slightly positively charged and this cause the formation of hydrogen bonds.

Question 5

What is the primary structure of proteins?

Answer 5

Is the sequece of R-Groups along the polypeptide chain.

Question 6

What is the structure of the backbone of polypeptide common to all proteins?

Answer 6

-N-C-C-

Question 7

What are PSI and PHI bonds and why are they important?

Answer 7

They are two single bonds that are therefore free to rotates and their angle determine the secondary structure of proteins.

Question 8

Describe the Hydrogen bond and how is it formed:

Answer 8

The hydrogen bonds is the result of the polarisation of the bond between and hydrogen and an electronegative atom that gives a partial positive charge to the hydrogen that cause it to interact with another electrongative atom. It also involves a partial sharing of electrons that make it partially covalent.

Question 9

What is the secondary structure of proteins?

Answer 9

Is the local folding of proteins and the conformation of backbones.

Question 10

What are the two possible types of secondary structure in proteins?

Answer 10

Alpha helix and beta strands.

Question 11

Describe Alpha Helix:

Answer 11

Is a right handed helix stabilized by the hydrogen bonds in which the side chain face outwards.

Question 12

Describe beta strands:

Answer 12

The polypeptide doesn’t form a coil, instead it zigzag and is less stable than Alpha Helix because it doesn’t contain hydrogen bonds. They can form beta sheets by forming hydrogen bonds between two strands.

Question 13

What are the three different types of beta sheets?

Answer 13

Parallel Antiparallel Mixed