Primary Structure of Proteins

Q.

Why are alpha helices Important?

Q.

Explain the terms primary and secondary structure of proteins. What is the difference between $\alpha -$ helix and $\beta -$ pleated sheet structure of proteins?

Q. At some points a protein molecule may be folded back on itself. This is called _____structure and folds or coils are held together in place by ______

1. $2^{\circ },$ H-bonds
2. $2^{\circ },$ peptide bonds
3. $3^{\circ },$ H-bonds
4. $1^{\circ },$ peptide bonds

Q. Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): Proteins are made up of alpha amino acids.
Reason (R): During denaturation, secondary and tertiary structure of proteins are destroyed.

1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true

Q. A peptide is a short chain of amino acids. The amino acids in a peptide are connected to one another in a sequence by bonds called peptide bonds. Typically, peptides are distinguished from proteins by their shorter length, although the cut-off number of amino acids for defining a peptide and protein can be arbitrary.
Peptides are generally considered to be short chains of two or more amino acids. Meanwhile, proteins are long molecules made up of multiple peptide subunits, and are also known as polypeptides. Proteins can be digested by enzymes (other proteins) into short peptide fragments. Among cells, peptides can perform biological functions. For example, some peptides act as hormones, which are molecules that when released from cells affect other areas of the body.
A decapeptide (Mol. Wt. 796 g/mol) on complete hydrolysis gives glycine (Mol. Wt. 75 g/mol), alanine and phenylalanine. Glycine contribute 47% to the total weight of the hydrolyzed product.The number of glycine units in the decapeptide is:

Q. Out of the following, which type of interaction is responsible for the stabilisation of $\alpha$-helix structure of proteins?

1. Hydrogen bonding
2. vander Waals forces
3. Ionic bonding
4. Covalent bonding

Q.

Proteins fulfil several functions in living systems. An example of a protein which acts as a hormone is

[KCET 1985]

1. Casein

2. Oxytocin

3. Trypsin

4. Keratin

Q.

Proteins are built up of

[CPMT 1981, 99; BHU 1987; CBSE PMT 2001;

MP PMT 1987, 96; KCET 1984]

1. Alcohols

2. Dicarboxylic acids

3. Amino acids

4. Hydroxy acids

Q.

Proteins are built up of

[CPMT 1981, 99; BHU 1987; CBSE PMT 2001;

MP PMT 1987, 96; KCET 1984]

1. Dicarboxylic acids

2. Amino acids

3. Alcohols

4. Hydroxy acids

Q. A peptide made up of n number of amino acids contains how many peptide linkages?

1. $n$
2. $2n-1$
3. $n+1$
4. $n-1$

Q. The most likely change occurring in a protein sample when treated with $6\text{M}HCl$ is:

1. Formation of peptide bond
2. Oxidation of disulphide bond
3. Hydrolysis of peptide bond
4. Formation of disulphide bond

Q. Explain the terms primary and secondary structure of proteins. What is the difference between $\alpha$-helix and $\beta$-pleated sheet structure of proteins?

Q.

Proteins fulfil several functions in living systems. An example of a protein which acts as a hormone is

[KCET 1985]

1. Casein

2. Oxytocin

3. Trypsin

4. Keratin

Q. Secondary structure of protein refers to ?

1. sequence of amino acids in polypeptide chain
2. bonds between alternate polypeptide chains
3. folding patterns of polypeptide chain
4. bonding between ${NH}_3^{+}$ and ${COO}^{-}$ of two peptides

Q. An $\alpha$-helix is the example of which type of protein structure?

1. Primary
2. Secondary
3. Tertiary
4. Quaternary

Q. How to check for mutarotationa / reducing sugars?

Q. An $\alpha$-helix is the example of which type of protein structure?

1. Primary
2. Secondary
3. Tertiary
4. Quaternary

Q. The number of chiral centres in penicillin is ________.

Q. Which among the following represent chelating ligands?

1. $C{N}^{-}$
2. $O{H}^{-}$
3. $2,2-dipyridyl$
4. $SC{N}^{-}$

Q.

Proteins fulfil several functions in living systems. An example of a protein which acts as a hormone is

[KCET 1985]

1. Casein

2. Oxytocin

3. Trypsin

4. Keratin

Q.

Proteins fulfil several functions in living systems. An example of a protein which acts as a hormone is

[KCET 1985]

1. Casein

2. Oxytocin

3. Trypsin

4. Keratin

Q.

Proteins are built up of

[CPMT 1981, 99; BHU 1987; CBSE PMT 2001;

MP PMT 1987, 96; KCET 1984]

1. Dicarboxylic acids

2. Amino acids

3. Alcohols

4. Hydroxy acids