Protein structure

Question 1

How are amino acids linked?

Answer 1

By peptide bonds

Question 2

What is the protein function dependent on?

Answer 2

Structure

Question 3

What are some properties of the peptide bond?

Answer 3

• Stable
• Cleaved by proteases or peptidases
• Partial double bond
• flexibility

Question 4

What is a protein vs peptide?

Answer 4

Protein = if it is functional and synthesized by a cell
Peptide = bit of protein broken off

Question 5

How do linear protein chains fold?

Answer 5

• Linear chains fold in different shapes to form 3D structures:
• Determined by charged interactions, flexibility, amino acid sequence, and physical dimensions

Question 6

What is the primary protein structure?

Answer 6

Linear sequence of amino acids

Question 7

What is the secondary protein structure?

Answer 7

alpha helix or beta pleated sheets formation due to H+ bonds between amino acids – determined by local interactions between side chains and sequence of amino acids.

Question 8

What is the tertiary protein structure?

Answer 8

Overall 3D conformation of a protein. Confirmation can change with temperature or pH.

Question 9

What is the Quaternary protein structure?

Answer 9

3D structure of protein with multiple subunits.

Question 10

What forces hold proteins together?

Answer 10

• Van der Waals
• Hydrogen bonds
• Hydrophobic forces
• ionic bonds
• Disulphide bonds

Question 11

What are Van der Waal forces?

Answer 11

Weak attractive/repulsive force between all atoms due to fluctuating electrical charge.

Question 12

What are Hydrogen bonds?

Answer 12

Interaction between polar groups (involving a hydrogen and an oxygen, nitrogen

Question 13

What are Hydrophobic forces?

Answer 13

• As uncharged and non-polar side chain are repelled by water, hydrophobic side chains form tightly packed cores in the interior of proteins, excluding water molecules.

Question 14

What are ionic bonds?

Answer 14

between fully/partially charged groups.

Question 15

What are disulphide bonds?

Answer 15

very strong covalent bonds between sulphur atoms

Question 16

How do we determine a protein structure?

Answer 16

X-ray diffraction of protein crystals

Question 17

What is an important form of a protein?

Answer 17

An enzyme which bind reactants and convert them to product, then they release the products and return to their original form

Question 18

What is the structure of haemoglobin?

Answer 18

• It is a protein and it has a quaternary structure. - It consists of two pairs of different proteins, designated the α and β chains
• It has a porphyrin ring which holds an iron atom (heme)