2.3.5 - Levels Of Protein Structure

Question 1

Describe The Primary Structure Of A Protein
(3 Points)

Answer 1

~ Sequence of amino acids bonded by peptide bonds in the polypeptide chain.

~ DNA determines it, by instructing the cell to add certain amino acids in specific quantities in a certain sequence, affecting the shape and function.

~ Determines the 3D structure of a protein therefore its function.

Question 2

Describe The Secondary Structure Of A Protein
(3 Points)

Answer 2

~ Occurs when the weak negatively charged nitrogen and oxygen atoms interact with the weak positively charged hydrogen atoms to form hydrogen bonds.

~ Hydrogen bonds cause alpha helix or beta pleated sheets to form within the protein.

~ Hydrogen bonds can be broken by high temperatures and pH changes.

Question 3

Describe ‘Alpha Helix’ In The Secondary Structure
(2 Points)

Answer 3

~ Occurs when the hydrogen bonds form between every fourth peptide bond.

~ Is a coil.

Question 4

Describe ‘Beta Pleated Sheet’ In The Secondary Structure
(2 Points)

Answer 4

~ Forms when the proteins folds so that two parts of the polypeptide chain are parallel to each other enabling hydrogen bonds to form between parallel peptide bonds.

~ Parallel.

Question 5

Describe The Tertiary Structure Of A Protein
(3 Points)

Answer 5

~ Coiled or folded chain of amino acids is then coiled and folded further.

~ Additional bonds form between the R groups. E.g. Hydrogen bonds, ionic bonds, disulphide bonds and weak hydrophobic interactions.

~ For proteins made from a single polypeptide this gives them their final 3D structure.

Question 6

Describe ‘Hydrogen Bonds’ In The Tertiary Structure Of A Protein

Answer 6

Occur between the R groups.

Question 7

Describe ‘Ionic Bonds’ In The Tertiary Structure Of A Protein
(2 Points)

Answer 7

~ Are attractions between negative and positive charges on different parts of the molecule.

~ Occurs between charged R groups.

Question 8

Describe ‘Disulphide Bonds’ In The Tertiary Structure Of A Protein

Answer 8

Whenever two molecules of the amino acid cysteine come closer together the sulfur atom in one cysteine bonds the sulfur atom in the other cysteine.

Question 9

Describe ‘Hydrophobic & Hydrophilic Interactions’ In The Tertiary Structure Of A Protein

Answer 9

~ When hydrophobic groups are closer together in the protein, they tend to clump together.

~ Meaning hydrophilic groups are likely to be pushed to the outside, affecting how the protein folds up into its final structure.

Question 10

Describe The Quaternary Structure Of A Protein
(4 Points)

Answer 10

~ Occurs in proteins that have more than one polypeptide chain working together.

~ Is the way that polypeptide chains are assembled together.

~ For proteins made from more than one polypeptide chain, this is the proteins final structure.

~ Same bonds responsible for maintaining the tertiary structure of a protein will also be involved in forming this structure.