All questions of Biomolecules for NEET Exam

Competitive Inhibition and Km

Competitive inhibition is a type of enzyme inhibition where an inhibitor molecule, similar in structure to the substrate, competes with the substrate for binding to the active site of the enzyme. This type of inhibition does not chemically change the inhibitor or the enzyme.

The rate of breakdown of the enzyme substrate complex is affected by competitive inhibition because the inhibitor competes with the substrate for binding to the active site. However, the inhibitor does not affect the rate of breakdown of the enzyme itself.

In competitive inhibition, the presence of the inhibitor increases the apparent affinity of the enzyme for the substrate, meaning that the concentration of substrate required to reach half of the maximum velocity (Vmax) of the reaction is decreased. This is reflected in a decrease in the Michaelis constant (Km) of the enzyme for the substrate.

Therefore, the incorrect statement is option C, which states that the presence of the competitive inhibitor decreases the Km of the enzyme for the substrate. In fact, the presence of the competitive inhibitor increases the affinity of the enzyme for the substrate, leading to a decrease in Km.

Understanding Lecithin
Lecithin is a vital biomolecule, particularly in cell membranes. It is a type of phospholipid that plays a crucial role in maintaining the structure and function of cellular membranes.
Characteristics of Lecithin
- Phosphorylated Glyceride: Lecithin is indeed a phosphorylated glyceride, which means it contains a glycerol backbone, fatty acids, and a phosphate group.
- Role in Cell Membranes: Its amphipathic nature (having both hydrophilic and hydrophobic parts) allows it to form bilayers that are essential for cell membrane integrity.
Why Other Options are Incorrect
- Palmitic Acid: This is a saturated fatty acid with 16 carbon atoms, not 18. It is not classified as unsaturated.
- Adenylic Acid: This compound is known as AMP (adenosine monophosphate). It consists of an adenosine molecule and one phosphate group, not a glucose phosphate molecule.
- Alanine Amino Acid: While alanine does contain an amino group (NH2) and a carboxylic acid group (COOH), the statement is misleading because these groups are specific to the alpha carbon of the amino acid, not "anywhere in the molecule."
Conclusion
In summary, option A is correct because it accurately describes lecithin as a phosphorylated glyceride found in cell membranes, highlighting its essential role in cellular structure. The other options misrepresent the chemical nature or structure of the biomolecules.

Enzymes are biological catalysts that increase the rate of chemical reactions within cells. Enzymes are mostly proteins that catalyze chemical reactions by lowering the activation energy required for the reaction to occur.

Explanation:

Enzymes lower activation energy:
Activation energy is the energy required to initiate a chemical reaction. In a chemical reaction, the reactant molecules need to collide with each other with sufficient energy to overcome the energy barrier and form the product. Enzymes lower the activation energy by providing an alternate pathway for the reaction to occur. This alternate pathway requires less energy, and hence the reaction proceeds at a faster rate.

Example:
The breakdown of sucrose into glucose and fructose requires an input of energy. In the presence of the enzyme sucrase, the activation energy required for the reaction is lowered, and the reaction occurs spontaneously.

Enzymes are specific:
Enzymes are specific to the reaction they catalyze, and they bind to the reactants at a specific site called the active site. The shape of the active site is complementary to the shape of the reactant molecule, and this specificity ensures that only the correct reactants bind to the enzyme.

Example:
The enzyme lactase catalyzes the breakdown of lactose into glucose and galactose. Lactase specifically binds to the lactose molecule, and the reaction occurs at a faster rate.

Enzymes are not consumed in the reaction:
Enzymes are not consumed in the reaction, and they can be used to catalyze the same reaction repeatedly. Enzymes are not changed by the reaction, and they can be reused multiple times.

Example:
The enzyme catalase catalyzes the breakdown of hydrogen peroxide into water and oxygen. Catalase is not consumed in the reaction, and it can be used to catalyze the same reaction repeatedly.

In conclusion, enzymes increase the rate of reaction by lowering the activation energy required for the reaction to occur. This allows the reaction to occur at a faster rate.

Antiparallel strands of a DNA molecule means that the phosphate groups at the start of two DNA strands are in opposite position (pole). DNA is composed of two polynucleotide strands, which form what looks like a ladder. The two polynucleotide strands run 'antiparallel' to each other, with nitrogenous bases projecting inwards. The term 'antiparallel' means that the strands run in opposite directions, parallel to one another. The antiparallel strands twist in a complete DNA structure, forming a double helix. It runs 3'-5' and 5'-3' linkage. The 5' and 3' mean "five prime" and "three prime", which indicate the carbon numbers in the DNA's sugar backbone. The 5' carbon has a phosphate group attached to it and the 3' carbon a hydroxyl (-OH) group. This asymmetry gives a DNA strand a "direction".,,..

Glycine is the simplest aminoacid..as its variable group R consists of H.....