Biological Molecules: Proteins

Question 1

Describe how a peptide bond is formed between two amino acids to form a dipeptide: (2 marks)

Answer 1

• A condensation reaction occurs between the two amino acids.
• Occurs in one amino acid’s amine group and the others carboxyl group

Question 2

The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how: (2 marks)

Answer 2

Hydrogen bonds from between one amino acid’s NH group and the others C=O group.

Question 3

Two proteins have the same number and type of amino acids but different tertiary structures. Explain why : (2 marks)

Answer 3

Different primary structure forms hydrogen bonds in different places.

Question 4

What bonds link amino acids together in a polypeptide chain?

Answer 4

Peptide bonds

Question 5

Haemoglobin is made up of multiple polypeptide chains. Name the level of structure that forms haemoglobins final 3D structure:

Answer 5

Quaternary

(because it is made up of multiple polypeptide chains)

Question 6

Which two substances are formed when two amino acid molecules join together?

Answer 6

Peptide
Water

Question 7

Explain how a change in the primary structure of a globular protein may result in a different three-dimensional structure:

Answer 7

• Sequence of amino acid changes
• Tertiary structure changes/folds in a different way
  -Bonds form in different places

Question 8

What is the bond between two amino acids called?

Answer 8

Peptide bond

Question 9

What is a dipeptide?

Answer 9

Two amino acids joined together

Question 10

What is a polypeptide chain?

Answer 10

Many amino acids joined together

Question 11

Explain how two enzymes with different amino acid sequences can catalyse the same reaction:

Answer 11

• Enzymes active site changes slightly
• Becomes complementary/specific to substrate
• Although enzymes tertiary structures are different, they change slightly to form enzyme-substrate complex.

Question 12

What is the primary structure of a protein?

Answer 12

Sequence of amino acids in its polypeptide chains.

Question 13

What is the secondary structure of a protein?

Answer 13

Folding of a polypeptide chain

Question 14

What type of bonding is found in the secondary structure?

Answer 14

Hydrogen bonds

Question 15

What type of bond are found in the primary structure?

Answer 15

Peptide bonds

Question 16

What causes the tertiary structure of a protein?

Answer 16

Hydrogen and ionic bonds between side groups of amino acids.

Question 17

What is the tertiary structure of a protein?

Answer 17

3D folding of the polypeptide chain

Question 18

During the secondary structure of a protein, proteins can either turn into a ________ or a __________.

Answer 18

Alpha helix
Beta pleated sheet

Question 19

What causes the secondary structure of a protein?

Answer 19

Hydrogen bonds between the groups of peptide bonds

Question 20

What 3 types of bonds are found in the tertiary structure of a protein?

Answer 20

• Hydrogen bonds
• Ionic bonds
• Disulfide bridges

Question 21

What is the quaternary structure of a protein?

Answer 21

2 or more polypeptide chains joined together.

Question 22

A protein is known as conjugated if it contains a _______.

Answer 22

Prosthetic group

Question 23

Name the bonds that join amino acids in the primary structure:

Answer 23

Peptide bonds

Question 24

What is the molecular formula of an amine group?

Answer 24

NH2

Question 25

How many amino acids are there?

Answer 25

20

Question 26

Amino acids are joined together by _______ reactions.

Answer 26

Condensation

Question 27

The bonds formed between amino acids are called _______ bonds.

Answer 27

Peptide