1.2b protein structure

Question 1

What determines protein structure?

Answer 1

amino acid sequence

Question 2

What are proteins polymers of?

Answer 2

amino acid monomers

Question 3

What are amino acids monomers of?

Answer 3

protein polymers

Question 4

What are amino acids linked by and what do they form?

Answer 4

• linked by peptide bonds

- to form polypeptides

Question 5

What are the 4 groups that amino acids are classified in according to their R groups?

Answer 5

• basic
• acidic
• polar
• hydrophobic

Question 6

What classifies and amino acid as basic?

Answer 6

R group results in:

• positively charged
• hydrophilic
• key component of R group is an amine group(NH)

Question 7

What classifies and amino acid as acidic?

Answer 7

R group results in:

• negatively charged
• hydrophilic
• key component of R group is a carboxylic acid group (COOH)

Question 8

What classifies an amino acid as Polar?

Answer 8

R group results in:

• slightly charged
• forms hydrogen bonds
• hydrophilic
• key component of R group is hydrophilic group (carbonyl C=O, hydroxyl OH, amine NH)

Question 9

what classifies an amino acid as hydrophobic?

Answer 9

R group results in:

• no charge, non-polar
• don’t form hydrogen bonds
• so don’t mix readily with water
• Key component of R group is hydrocarbon group CH

Question 10

How does the structure of different amino acids vary?

Answer 10

they have the same basic structure differing only in R group

• R groups vary in:
  
  • size
  • shape
  • charge
  • hydrogen bonding capacity
  • chemical reactivity

Question 11

What is responsible for the wide range of functions carried out by proteins?

Answer 11

the diversity of the R groups

Question 12

What is primary structure?

Answer 12

the sequence in which the amino acids are synthesised into the polypeptide

Question 13

What causes secondary structure?

Answer 13

hydrogen bonding along the backbone of the protein strand results in regions of secondary structure

Question 14

Give examples of secondary structure

Answer 14

• alpha helices
• parallel or anti-parallel beta-pleated sheets
• turns

Question 15

Describe tertiary structure

Answer 15

the polypeptide folds into a tertiary structure

Question 16

What stabilises tertiary structure?

Answer 16

interactions between R groups:

• hydrophobic interactions
• ionic bonds
• London dispersion forces
• hydrogen bonds
• disulfide bridges

Question 17

What are disulfide bridges?

Answer 17

covalent bonds between R groups containing sulfur

Question 18

What is quaternary structure?

Answer 18

Quaternary structure describes the spatial arrangement of subunits

Question 19

When does quaternary structure happen?

Answer 19

Quaternary structure exists in proteins with two or more connected polypeptide subunits

Question 20

What is a prosthetic group?

Answer 20

a non-protein unit tightly bound to a protein and necessary for its function

Question 21

What is the ability of hemoglobin to bind oxygen dependent on?

Answer 21

the non-protein haem group

Question 22

What is the effect of increasing temperature on interactions of the R groups?

Answer 22

• disrupts the interactions that hold the protein in shape
• the protein begins to unfold
• and eventually becomes denatured

Question 23

What is the effect of pH on interactions between R groups?

Answer 23

• the charges on acidic and basic R groups are affected by pH.
• as pH increases or decreases from the optimum
• the normal ionic interactions between charged groups are lost
• which gradually changes the conformation of the protein until it becomes denatured