Proteins

Proteins are complex biological molecules that perform a wide variety of functions within living organisms. One common secondary structure found in proteins is the -helix. The stabilization of this structure is crucial for the protein’s functionality and is primarily due to a specific type of interaction.

The -helix is a right-handed coil structure. The key factor stabilizing this structure is the hydrogen bonds that form between the backbone atoms of the polypeptide chain.

1. In an -helix, the N-H group of one amino acid forms a hydrogen bond with the C=O group of an amino acid four residues earlier (i.e., the nth amino acid forms a hydrogen bond with the (n+4)th amino acid).
2. This regular pattern of hydrogen bonding along the backbone results in the helix structure.
3. Hydrogen bonds are relatively strong dipole-dipole interactions where a hydrogen atom is attracted to a highly electronegative atom like oxygen or nitrogen.

To understand why other options are not correct:

• Ionic bonding: Although ionic bonds are crucial in proteins, especially those on the protein surface, they are not responsible for the -helix stabilization.
• Covalent bonding: While covalent bonds (such as disulfide bridges) can stabilize the overall tertiary structure of proteins, they do not play a role in stabilizing the -helix specifically.
• Van der Waals forces: Although these forces contribute to the stability of the protein structure, they are not the primary forces stabilizing the -helix.

Therefore, the correct answer is that hydrogen bonding is responsible for the stabilization of the -helix structure in proteins.

The correct answer is (B) : H-bonding interaction
Most of the time, H-bonding interaction is responsible for the stability of α-helix form.

The correct answer is 4
The given pentapeptide is :
ALA – GLY – LEU – ALA – VAL
It has 4 peptide linkages.

The correct answer is (C) : Primary structure
Primary structure of protein is unaffected by physical or chemical changes.

A tripeptide is formed by combining three amino acids, where the sequence of the amino acids matters. Since we are mixing two amino acids, valine (Val) and proline (Pro), each position in the tripeptide can be occupied by either valine or proline.
Number of combinations:
Total possible tripeptides = 2³ = 8.
Possible tripeptides:
1. Val-Val-Val
2. Val-Val-Pro
3. Val-Pro-Val
4. Val-Pro-Pro
5. Pro-Val-Val
6. Pro-Val-Pro
7. Pro-Pro-Val
8. Pro-Pro-Pro

Proteins are complex molecules that have different levels of structural organization: primary, secondary, tertiary, and quaternary structures. When it comes to the question of which structure remains intact after the coagulation of egg white upon boiling, we need to consider what happens physically and chemically during this process.

1. **Primary Structure**: This refers to the sequence of amino acids in a polypeptide chain. During coagulation, the primary structure remains intact as boiling does not break the peptide bonds between amino acids.

2. **Secondary Structure**: Refers to the folding of the polypeptide chain into alpha-helices and beta-sheets, stabilized by hydrogen bonds. Boiling can disrupt these hydrogen bonds, causing the secondary structure to alter.

3. **Tertiary Structure**: This is the overall three-dimensional shape of a protein. The intramolecular interactions like hydrogen bonds, ionic bonds, and disulfide bonds can be disrupted during the heat-induced coagulation.

4. **Quaternary Structure**: This applies to proteins with two or more polypeptide chains. Similar to tertiary structures, these interactions can be disrupted by heat.

Upon boiling, the egg white proteins denature, meaning that the secondary, tertiary, and quaternary structures are disrupted. However, the primary structure, which consists of the linear sequence of amino acids held together by covalent peptide bonds, remains unchanged.

The correct answer is Primary.

In conclusion, during the coagulation of egg white, only the primary structure of proteins remains intact, as chemical treatments like boiling affect non-covalent bonds and disulfide bonds, which are involved in the higher levels of protein structure.

To determine the type of amino acids obtained through the hydrolysis of proteins, we need to understand the structure of amino acids and the process of protein hydrolysis.

Proteins are composed of long chains of amino acids linked by peptide bonds. When these proteins undergo hydrolysis, the peptide bonds are broken, releasing individual amino acids.

The question presents four options:

• -Amino acids
• -Amino acids
• -Amino acids
• -Amino acids

The correct answer is -Amino acids. This is because the amino acids that constitute proteins are -amino acids, characterized by having the amino group ( ) attached to the alpha ( ) carbon, which is the first carbon adjacent to the carboxyl group ( ).

Each type of amino acid is named based on the position of the amino group relative to the carboxyl group:

• -Amino acids: Amino group is on the first carbon (alpha carbon).
• -Amino acids: Amino group is on the second carbon (beta carbon).
• -Amino acids: Amino group is on the third carbon (gamma carbon).
• -Amino acids: Amino group is on the fourth carbon (delta carbon).

Given that proteins are made up of -amino acids, the hydrolysis of proteins primarily yields -amino acids.

Therefore, the correct answer is:

• -Amino acids