L8: Proteins - Structure

Question 1

What makes up proteins?

Answer 1

• Amino acids

Question 2

What does an amino acid consist of?

Answer 2

• Amino group
• Carboxyl group
• R-group (side chain)

Question 3

Which groups do the peptide bond join?

Answer 3

• Carboxyl group (one molecule) and amino group (other molecule)

Question 4

What are amino acyl residues in a peptide?

Answer 4

• Amino acids with either OH (from carboxyl group) or H (from amino group) removed in the formation of a peptide bond
• One H2O removed per peptide bond

Question 5

What is the directionality of a protein?

Answer 5

• N-terminus to C-terminus

Question 6

What is the backbone of a polypeptide chain?

Answer 6

• The covalent linkages from one amino acid to the next

Question 7

What makes each amino acid different?

Answer 7

• R-group (side chain)

Question 8

Describe HYDROPHOBIC amino acids.

Answer 8

• Non-polar side chains

Question 9

Describe HYDROPHILIC amino acids.

Answer 9

• Charged and polar side chains

Question 10

Describe ACIDIC amino acids.

Answer 10

• Negatively charged

Question 11

Describe BASIC amino acids.

Answer 11

• Positively charged

Question 12

When does a polypeptide become a protein?

Answer 12

• When it’s folded

Question 13

What is the key concept in regards to protein structure?

Answer 13

• Sequence determines structure, structure determines function

Question 14

What are the 4 levels of protein structure

Answer 14

• Primary
• Secondary
• Tertiary
• Quaternary

Question 15

What can determine the structure of a protein?

Answer 15

• The makeup of R-groups in a polypeptide chain

Question 16

Describe the primary structure.

Answer 16

• The sequence of amino acids
• The amino acid sequence determines the protein’s 3D structure (i.e. the order, sequence & makeup of different aa’s)
• Order is determined by the DNA genetic code

Question 17

Describe the secondary structure.

Answer 17

• Results from the interaction of nearby amino acids.

Question 18

What are the two types of secondary structure?

Answer 18

• Alpha-helixes

- Beta-pleated sheets

Question 19

How does the secondary structure form?

Answer 19

• Carbonyl group in one peptide bond and an amide group in another form repetitive H-bonds

Question 20

How is the secondary structure stabilized?

Answer 20

• H-bonds w/ backbone atoms stabilize/keeps atoms together.

Question 21

Describe the tertiary structure.

Answer 21

• 3D shape of a protein
• 3D structure (fold) of the entire polypeptide
• Can be the final structure in some proteins

Question 22

How is the tertiary structure stabilized?

Answer 22

• By side-chain interactions (non-covalent & disulfide bonds)
• Interactions between side chains and backbone atoms

Question 23

Describe the quaternary structure.

Answer 23

• Results from interactions of protein subunits

Question 24

How is the quaternary structure stabilized?

Answer 24

• Stabilized by non-covalent interactions between subunits.