All questions of Biomolecules for NEET Exam

Monosaccharides are simple sugars that cannot be hydrolyzed into smaller carbohydrate units. They are the building blocks of more complex carbohydrates like disaccharides and polysaccharides. The composition of monosaccharides can vary, but they generally contain a carbon backbone of three to seven carbon atoms.

Explanation:

- Monosaccharides are carbohydrates that are composed of carbon, hydrogen, and oxygen atoms. The general formula for a monosaccharide is (CH2O)n, where n can range from 3 to 7.
- Monosaccharides are classified based on the number of carbon atoms they contain. Some examples include trioses (3 carbon atoms), tetroses (4 carbon atoms), pentoses (5 carbon atoms), hexoses (6 carbon atoms), and heptoses (7 carbon atoms).
- Trioses, such as glyceraldehyde and dihydroxyacetone, have three carbon atoms. They are the simplest monosaccharides.
- Tetroses, like erythrose and threose, have four carbon atoms.
- Pentoses, such as ribose and deoxyribose, have five carbon atoms. They are important components of nucleic acids.
- Hexoses, like glucose and fructose, have six carbon atoms. Glucose is a primary source of energy for living organisms, while fructose is commonly found in fruits and honey.
- Heptoses, like sedoheptulose and mannoheptulose, have seven carbon atoms. They are less common than other monosaccharides.
- It is important to note that although monosaccharides generally contain three to seven carbon atoms, there are exceptions. For example, deoxyribose, a pentose, is an important component of DNA and RNA, but it only contains five carbon atoms.
- Overall, the correct answer is option 'A' (3 to 7), as monosaccharides typically have a carbon backbone consisting of three to seven carbon atoms.

**Enzymes are biological catalysts that play a crucial role in speeding up chemical reactions in living organisms. Let's analyze each statement to determine which ones are correct:**

(i) Enzymes do not alter the overall change in free energy for a reaction.
- This statement is correct. Enzymes do not affect the overall change in free energy for a reaction. They only lower the activation energy required for the reaction to occur, but they do not change the energy difference between the reactants and products.

(ii) Enzymes are proteins whose three-dimensional shape is key to their functions.
- This statement is correct. Enzymes are proteins, and their three-dimensional shape is critical for their proper functioning. The active site of an enzyme, where the substrate binds and the reaction takes place, is precisely shaped to accommodate specific substrates.

(iii) Enzymes speed up reactions by lowering activation energy.
- This statement is correct. Enzymes work by lowering the activation energy required for a chemical reaction to occur. Activation energy is the energy input needed to start a reaction, and enzymes facilitate this process by providing an alternative pathway with a lower energy barrier.

(iv) Enzymes are highly specific for reactions.
- This statement is correct. Enzymes are highly specific for particular reactions. Each enzyme is designed to catalyze a specific chemical reaction or a group of closely related reactions. This specificity is determined by the enzyme's active site and its ability to recognize and bind to specific substrates.

(v) The energy input needed to start a chemical reaction is called activation energy.
- This statement is correct. Activation energy refers to the energy input needed to initiate a chemical reaction. It is the energy required to break the bonds of the reactant molecules and reach the transition state, from which the reaction proceeds to form the products.

**In conclusion, all of the given statements are correct. Enzymes do not alter the overall change in free energy, their three-dimensional shape is crucial for their function, they lower activation energy, they are highly specific for reactions, and activation energy is the energy input needed to start a chemical reaction. Therefore, the correct answer is option 'D'.

Proteins constitute a significant portion of the cellular mass, making up about 10-15% of it. This makes them vital for numerous cellular functions, including acting as enzymes, structural components, and signaling molecules.

Assertion (A): Lipids, despite their smaller molecular weights, are part of the acid insoluble fraction.
The assertion is true. Lipids, which include fats, oils, and phospholipids, typically have lower molecular weights compared to proteins and carbohydrates. However, they are classified as part of the acid insoluble fraction due to their hydrophobic nature.
Reason (R): Lipids form structures like cell membranes that are not water soluble, leading to their inclusion in the macromolecular fraction.
The reason is also true. Lipids indeed play a crucial role in forming cell membranes, which are essential for maintaining cellular integrity and function. Their hydrophobic properties prevent them from dissolving in water, which is why they are categorized in the acid insoluble fraction.
Relationship between A and R:
- Both assertion and reason are true.
- The reason provides a correct explanation for the assertion. Lipids are included in the acid insoluble fraction not just because of their molecular weight but primarily due to their solubility characteristics.
Conclusion:
- Since both statements are true and R correctly explains A, the correct answer is option 'A': Both A and R are true, and R is the correct explanation of A.
This understanding is crucial in the context of biochemistry, especially for NEET aspirants, as it highlights the importance of lipid solubility and structure in biological systems.

The correct answer is option 'A': R-groups.

Amino acids are the building blocks of proteins. There are 20 different amino acids that can combine in various ways to form different proteins. Each amino acid consists of a central carbon atom (called the alpha carbon) bonded to four different groups: an amino group, a carboxylic group, a hydrogen atom, and a unique side chain, also known as the R-group.

The R-group, or side chain, is what differentiates one amino acid from another. It can vary in size, shape, charge, polarity, and chemical properties. The R-group determines the unique characteristics and functions of each amino acid.

The side chain can be categorized into different groups based on its chemical properties. Some common categories of R-groups include:

1. Nonpolar side chains: These R-groups are hydrophobic, meaning they do not interact with water. Examples include glycine, alanine, valine, leucine, isoleucine, proline, methionine, phenylalanine, and tryptophan.

2. Polar side chains: These R-groups are hydrophilic, meaning they interact with water. Examples include serine, threonine, cysteine, tyrosine, asparagine, and glutamine.

3. Charged side chains: These R-groups are either positively charged (basic) or negatively charged (acidic). Examples of basic side chains include lysine, arginine, and histidine. Examples of acidic side chains include aspartic acid and glutamic acid.

4. Specialized side chains: These R-groups have unique properties that do not fit into the above categories. For example, cysteine can form disulfide bonds, and glycine is the smallest amino acid.

The R-group determines how an amino acid interacts with its environment and other amino acids in a protein. It affects the protein's structure, stability, and function. The specific arrangement and composition of amino acids in a protein determine its three-dimensional structure and ultimately its biological activity.

In summary, the 20 different amino acids have different R-groups, which are responsible for their unique properties and functions. The R-group determines how amino acids interact with their environment and other amino acids in a protein, ultimately influencing the structure and function of the protein.

Enzymes are essential for the survival of cells

Enzymes are biological molecules that act as catalysts, speeding up chemical reactions within cells. Without enzymes, many essential cellular processes would occur too slowly to sustain life. Enzymes are involved in a wide range of functions within cells, including metabolism, growth, and repair.

Enzymes are needed for:
- Breaking down nutrients into smaller molecules that can be used by the cell for energy and building materials
- Facilitating the synthesis of important cellular molecules
- Helping cells respond to signals from their environment
- Repairing damage to cellular components

Importance of enzymes in cell survival

Enzymes are crucial for the functioning of cells because they lower the activation energy required for chemical reactions to occur. This allows cells to carry out essential processes at a much faster rate than would be possible without enzymes.

Enzymes are highly specific in their actions, meaning that each enzyme catalyzes a particular reaction. This specificity is essential for cells to regulate their metabolism and maintain homeostasis. Without enzymes, cells would not be able to efficiently carry out the chemical reactions necessary for their survival.

In conclusion, enzymes are indispensable for the survival of cells. They play a vital role in facilitating essential cellular processes and maintaining the overall function of the cell. Without enzymes, cells would not be able to function properly and would ultimately perish.

Understanding the Acid Soluble Pool
The acid soluble pool within cells plays a crucial role in cellular metabolism and functionality. Here's a detailed explanation of its primary role:
Definition of the Acid Soluble Pool
- The acid soluble pool is a component of the cytoplasm, consisting largely of small molecules and metabolites.
- It includes various organic compounds such as amino acids, nucleotides, and intermediary metabolites.
Composition and Functions
- Cytoplasmic Composition:
- The acid soluble pool represents the diverse array of small molecules found within the cytoplasm, crucial for metabolic activities.
- Metabolic Pathways:
- These small molecules act as substrates and cofactors in various metabolic pathways, facilitating biochemical reactions necessary for cell survival and function.
- Cellular Signaling:
- Components of the acid soluble pool are involved in signaling pathways, helping cells respond to environmental changes and maintain homeostasis.
Importance in Cellular Processes
- Energy Production:
- While not primarily an energy storage reservoir, the acid soluble pool contains key metabolites involved in the energy production processes, such as glycolysis and the citric acid cycle.
- Biosynthesis:
- It provides the building blocks for synthesizing larger biomolecules, including proteins and nucleic acids, essential for growth and repair.
Conclusion
In summary, the acid soluble pool is integral to cellular function as it reflects the cytoplasmic composition of small molecules that support various metabolic activities, making option 'B' the correct choice.

Non-competitive inhibitor:
Non-competitive inhibitors are molecules that bind to an enzyme at a site other than the active site. They do not resemble the substrate in structure. These inhibitors inhibit enzyme activity by changing the shape of the enzyme, making it less effective in catalyzing the reaction.

Mechanism of action:
- Non-competitive inhibitors bind to the enzyme at an allosteric site, causing a conformational change in the enzyme.
- This conformational change may prevent the substrate from binding to the active site or inhibit the catalytic activity of the enzyme.
- Since non-competitive inhibitors do not compete with the substrate for the active site, increasing substrate concentration will not overcome their inhibitory effect.

Characteristics:
- Non-competitive inhibitors do not compete with the substrate for binding to the enzyme.
- They can bind to the enzyme-substrate complex as well as the free enzyme.
- The inhibition by non-competitive inhibitors is not easily reversible.
- These inhibitors are not affected by changes in substrate concentration.

Examples:
- Heavy metal ions like mercury and lead are examples of non-competitive inhibitors.
- Drugs like aspirin and certain antibiotics also act as non-competitive inhibitors of specific enzymes.
In conclusion, non-competitive inhibitors are molecules that bind to an enzyme at a site other than the active site, causing a conformational change that inhibits enzyme activity.

Lipids, though they do not have high molecular weights like other macromolecules, are part of the acid insoluble fraction because they arrange into structures like cell membranes. When tissues are ground up, these membranes break into vesicles that are not water-soluble, leading to their categorization as part of the acid insoluble fraction despite their smaller size.