Protein Structure & Function

Question 1

Primary Structure

Answer 1

Amino acid sequence

• Peptide Bonds

Question 2

Secondary Structure

Answer 2

– Alpha helices
– Beta sheets
• Hydrogen Bonds

Question 3

Tertiary Structure

Answer 3

• Ionic Bonds
• Hydrogen Bonds
• Hydrophobic Interactions
• Van der Waals Forces
• Disulfide Bonds

the overall 3D structure of the protein

Disulfide Bonds:
Only between 2 Cysteines
A covalent bonds forms
between the Sulfur atoms.

Question 4

Quaternary Structure

Answer 4

– Protein Complexes
• Non Covalent Interactions
– H-Bonds
– Ionic Bonds
– Hydrophobic Interactions
– Van der Waals Forces
• Covalent Bonds
– Disulfide Bonds

Question 5

α-helix

Answer 5

The “bundle” of α-helices in CFTR forms a tunnel for Cl- ions to flow through.

Question 6

β-sheet

Answer 6

formed by hydrogen bonds between backbone atoms on adjacent regions of the peptide backbone

Question 7

Hydrogen Bonding

Answer 7

attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. H has a partial positive charge.

Question 8

Hydrophobic Interactions

Answer 8

“water-fearing,” and it describes the segregation and apparent repulsion between water and nonpolar substances.

Question 9

Hydrophilic

Answer 9

Having a tendency to mix with, dissolve in, or be wetted by water.

Question 10

van der Waals Forces

Answer 10

weak, short-range electrostatic attractive forces between uncharged molecules, arising from the interaction of permanent or transient electric dipole moments.

Question 11

Covalent Bonding

Answer 11

a molecular bond (non metal and a non metal), is a chemical bond that involves the sharing of electron pairs between atoms.

Question 12

Disulfide Bonds

Answer 12

a single covalent bond between the sulfur atoms to two amino acids called cysteine.

Question 13

Ionic Bonding

Answer 13

complete transfer of valence electron(s) between atoms. It is a type of chemical bond that generates two oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively charged anion.

Question 14

Denatured

Answer 14

A process in which proteins or nucleic acids lose the quaternary structure, tertiary structure and secondary structure which is present in their native state

Question 15

Explain in chemical and structural terms, what similar amino acids are

Answer 15

The term structure when used in relation to proteins, takes on a much more complex … These side chains confer different chemical, physical and structural … While the amino acid sequence makes up the primary structure of the protein.

Question 16

Compare and contrast between primary, secondary, tertiary, and quaternary structure

Answer 16

Primary: Is a sequences of a chain of Amino acids
Secondary: Occurs when the sequence of amino acids are linked by Hydrogen Bonds
Tertiary: occurs when certain attractions are present between alpha helices and pleated sheets
Quaternary: is a protein consisting of more than one amino aid chain

Question 17

Explain how changing a protein’s primary structure (by mutating an amino acid) can affect its
function.

Answer 17

Primary structure, the amino acid sequence, affects the secondary structure, which affects the tertiary structure, which affects the quaternary structure (if any). In short, the amino acid sequence affects the shape of the protein, and the function of a protein depends on its shape.

Question 18

When you make ceviche, you denature proteins in a slightly different way. You denature proteins
by adding large amounts of lime juice. Why do you think lime juice denatures proteins?

Answer 18

Citric acid denatures the protein. Heat and acid affect proteins (found in meat, fish, etc). The term is denaturing which essentially means to render non-functional in a irreversible fashion.

Question 19

Which of the following are advantages of constructing a protein of many amino acid monomers

Answer 19

A no-longer-needed protein can be broken down and a different protein constructed from the same
monomers.
B) An animal can eat a plant protein, break it down to amino acids and use these to construct its own
proteins.
C) A myriad of proteins can be constructed from the 20 amino acids by simply varying their sequence.

Question 20

At which structural level(s) one can alter the function of a protein:

Answer 20

ALL OF THEM

Question 21

All of the following contain amino acids EXCEPT
A) hemoglobin.
B) cholesterol.
C) antibodies.
D) enzymes.
E) aquaporins.

Answer 21

CHOLESTROL

Question 22

The bonding of two amino acid molecules to form a larger molecule requires

Answer 22

A) removal of a water molecule

D) formation of a peptide bond

Question 23

Which type of interaction stabilizes the alpha helix and the beta pleated sheet structures of proteins?

Answer 23

Hydrogen Bonds

Question 24

8. A hydrophilic R-group of an amino acid in hemoglobin would NOT be attracted to:
   A) the water molecules surrounding hemoglobin.
   B) a hydrophobic amino acid R group of hemoglobin.
   C) a charged amino acid R group of hemoglobin.
   D) a polar amino acid R group of hemoglobin.
   E) an amino acid R group of hemoglobin containing an –OH group.

Answer 24

B) a hydrophobic amino acid R group of hemoglobin.

Question 25

The structural level of a protein least affected by a disruption in hydrogen bonding is the

Answer 25

primary level.

Question 26

Humans can produce the amino acid alanine from other components in the body, but valine cannot
be produced in the human body. From this you can conclude:

Answer 26

Alanine is a non-essential amino acid

Valine is an essential amino acid