Concept explainers
Interpretation:
Effect of hydrophobic interactions on the tertiary structure of proteins must be explained.
Concept introduction:
Proteins are biological
Amino acids are molecules that contain both amino group and
Structure of proteins plays a very important role in their function. Proteins are very complex in structure. Structure of protein is studied in four levels: Primary, Secondary, Tertiary and Quaternary structure.
Primary structure:
Primary structure of a protein is the sequence of amino acids in each polypeptide chain that make up the protein. The ultimate structure of protein depends on this sequence.
Secondary Structure:
The peptide backbone of polypeptide chain folds onto itself due to interactions between amino and carboxylic acid residues in the peptide backbone. This folding of polypeptide chains give proteins a unique shape, this makes the secondary structure of proteins.
Two kinds of shapes are formed in the secondary structure of proteins:
- α-Helix: The backbone folds itself to form a helical structure. Hydrogen bonds are formed with the chain.
- ß-Pleated sheet: The polypeptide chains are stacked side by side. The outer N-H and C=O form intermolecular hydrogen bonds and give a very rigid structure. These hydrogen bonds are formed between neighboring polypeptide chains unlike α-Helix.
Tertiary Structure:
The overall 3-Dimensional structure of a protein formed when regions in secondary structure fold together, is called the tertiary structure of a protein. The tertiary structure of a protein is primarily due to interactions between the side chains of the polypeptide chains or the side chains in the backbone of the polypeptide.
The interactions between the side chains include: hydrogen bonding, ionic interactions, dipole-dipole interactions and London dispersion forces. Another important interaction that makes up the tertiary structure of proteins are hydrophobic interactions between the hydrophobic r groups of side chain of amino acids.
One special kind of covalent bond is also involved in forming the tertiary structure of proteins that is the disulfide bond formed between the -SH residues of cysteine.
Quaternary Structure:
When proteins contain more than one polypeptide chain, the final arrangement of each polypeptide subunit is known as the quaternary structure. The same kinds of interactions that make the tertiary structure are also involved in forming the quaternary structure.
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Chapter 22 Solutions
Introduction to General, Organic and Biochemistry
- 22-53 Do iron and zinc ions play role in protein structure? If so, what is the role for either or both?arrow_forward22-49 Based on your knowledge of the chemical properties of amino acid side chains, suggest a substitution for leucine in the primary structure of a protein that would probably not change the character of the protein very much.arrow_forward22-62 Distinguish between intermolecular and intramolecular hydrogen bonding between backbone groups. Where in protein structures do you find one, and where do you find the other?arrow_forward
- 22-44 How can a protein act as a buffer?arrow_forward22-101 Using what you know about protein denaturation, what is one reason you must maintain a body temperature in a strict range?arrow_forward22-85 Denaturation is usually associated with transitions from helical structures to random coils. If an imaginary process were to transform the keratin in your hair from an (-helix to a (-pleated sheet structure, would you call the process denaturation? Explain.arrow_forward
- 22-89 What kind of noncovalent interaction occurs between the following amino acids? (a) Valine and isoleucine (b) Glutamic acid and lysine (c) Tyrosine and threonine (d) Alanine and alaninearrow_forward22-104 Why is collagen not a very good source of dietary protein?arrow_forward22-6 The members of which class of proteins are insoluble in water and can serve as structural materials?arrow_forward
- 22-9 What is the difference in structure between tyrosine and phenylalanine?arrow_forward22-61 Polyglutamic acid (a polypeptide chain made only of glutamic acid residues) has an a-helix conformation below pH 6.0 and a random-coil conformation above pH 6.0. What is the reason for this conformational change?arrow_forward22-92 Write the expected products of the acid hydrolysis of the following tetrapeptide:arrow_forward
- Introduction to General, Organic and BiochemistryChemistryISBN:9781285869759Author:Frederick A. Bettelheim, William H. Brown, Mary K. Campbell, Shawn O. Farrell, Omar TorresPublisher:Cengage Learning