Topic 1.2 Biological molecules

Question 1

Proteins are a macromolecule made up of…

Answer 1

amino acids

Question 2

What bond forms between 2 amino acids?

Answer 2

peptide bond

Question 3

What groups does an amino acid contain?

Answer 3

• amine group (-NH2)
• carboxyl group (-COOH)
• R group (variable)

Question 4

Name the different bonds that can form in a protein

Answer 4

• peptide
• hydrogen
• disulfide
• ionic

Question 5

How do hydrogen bonds form within a protein?

Answer 5

tiny negative charges on the oxygen of the carboxyl group is attracted to the tiny positive charges of the hydrogen of the amine group

Question 6

State the properties of hydrogen bonds

Answer 6

• weak
• break easily and reform if pH or temperature conditions change
• potential to form lots of H bonds

Question 7

Why are hydrogen bonds important in proteins?

Answer 7

in the folding and coiling of the polypeptide chain

Question 8

How do disulfide bonds form within a protein?

Answer 8

when 2 cysteine molecules are close together and oxidation reaction occurs between the 2 sulfur containing groups to form a covalent bond
(cysteine has the R group CH2-SH)

Question 9

Compare hydrogen and disulfide bonds

Answer 9

• hydrogen bonds occur frequently, disulfide bonds don’t occur often
• disulfide bonds are much stronger than hydrogen bonds

Question 10

What is the importance of disulfide bonds in proteins?

Answer 10

they’re important in holding the folded polypeptide chains in place

Question 11

How do ionic bonds form within a protein?

Answer 11

ionic bonds can form between some of the strongly positive and negative amino acid side chains buried deep in the protein, the links are known as salt bridges (strong but not common)

Question 12

How can the protein structure be described?

Answer 12

• primary
• secondary
• tertiary
• quaternary

Question 13

What is the primary structure of a protein?

Answer 13

the sequence of amino acids in a polypeptide chain held together by peptide bonds

Question 14

What is the secondary structure of a protein?

Answer 14

the arrangement of the polypeptide chain into regular repeating structure, held together by hydrogen bonds e.g. alpha-helix or beta pleated-sheet (most fibrous proteins have this structure)

Question 15

What is the tertiary structure of a protein?

Answer 15

a level of 3D organisation imposed on top of the secondary structure. Hydrogen, disulfide and ionic bonds help to hold 3D shapes in place e.g. globular proteins

Question 16

What is the quaternary structure of a protein?

Answer 16

only seen in proteins containing several polypeptide chains when they fit together in 3D e.g. haemoglobin

Question 17

Describe the structure of a globular protein

Answer 17

has a tertiary and quaternary structure
held by hydrogen bonds
hydrophilic group on the outside of the molecule