Class Xii MCQ Test- Biomolecules

DNA is mainly localized in the nucleus. This is because the nucleus is the control center of the cell and contains the genetic material, which is DNA. DNA carries the instructions for the functioning and development of the organism. While small amounts of DNA can also be found in other organelles such as mitochondria and chloroplasts, the majority of the DNA is housed within the nucleus. The nucleus provides a protected environment for the DNA, ensuring its integrity and allowing for proper gene expression and regulation.

DNA molecules can duplicate themselves through a process called replication. During replication, the DNA molecule unwinds, and each strand serves as a template for the synthesis of a new complementary strand. This results in two identical DNA molecules, each containing one original strand and one newly synthesized strand. Replication is a vital process for the transmission of genetic information from one generation to the next and is essential for cell division and growth. Translation and transcription are processes involved in protein synthesis and do not directly involve the duplication of DNA molecules. Therefore, the correct answer is replication.

Beri beri is a condition caused by a deficiency of Vitamin B1. It is characterized by symptoms such as muscle weakness, fatigue, nerve damage, and heart problems. The lack of Vitamin B1 in the diet leads to impaired energy production in the body, affecting the functioning of various organs and systems. Therefore, the correct answer is Beri beri.

Both statements are true. DNA contains deoxyribose sugar while RNA contains ribose sugar. Additionally, DNA contains thymine as one of its bases, while RNA contains uracil instead of thymine.

Thymine is not present in RNA. RNA contains the base Uracil instead of Thymine. Thymine is found in DNA, where it pairs with Adenine. In RNA, Uracil pairs with Adenine instead. Therefore, Thymine is the base that is not present in RNA.

Vitamin B is a water-soluble vitamin, meaning it dissolves in water and can be easily absorbed by the body. Unlike fat-soluble vitamins, such as Vitamins A, E, and K, which are stored in the body's fat tissues, water-soluble vitamins are not stored and any excess amounts are excreted in urine. Vitamin B plays a crucial role in various bodily functions, including energy production, metabolism, and the health of the nervous system. It is found in a variety of foods, such as whole grains, meat, fish, dairy products, and leafy greens.

Both Fehling's solution and Tollen's reagent cannot be used to test for cellulose. Fehling's solution is used to test for the presence of reducing sugars, while Tollen's reagent is used to test for the presence of aldehydes. Cellulose, on the other hand, is a complex carbohydrate and does not contain any reducing sugars or aldehydes, which is why these tests are not suitable for testing cellulose.

The correct answer is "All of these". This means that all of the statements mentioned in the question are correct. Monosaccharides are indeed sugars, polysaccharides are non-sugars, and maltose and lactose are reducing sugars.

A zwitter ion is a neutral ion because it contains both positive and negative charges, which cancel each other out, resulting in a net charge of zero. This type of ion is formed when a molecule or compound has both acidic and basic functional groups, allowing it to donate and accept protons, thus maintaining a neutral charge overall.

In the ß-sheet of proteins, conformers are held together by intermolecular H-bonds. These bonds form between the hydrogen atoms of one conformer and the electronegative atoms (such as oxygen or nitrogen) of another conformer. The intermolecular H-bonds provide stability to the ß-sheet structure and help to maintain its shape. Intramolecular H-bonds, on the other hand, occur within a single conformer and do not contribute to the bonding between different conformers in the ß-sheet. Therefore, the correct answer is intermolecular H-bond.

The correct answer is "Inversion." Inversion refers to a change in the sign of rotation observed when a compound undergoes a chemical reaction. In the case of sucrose hydrolysis, the dextro(+) rotation changes to levo(-) rotation. This change in rotation is known as inversion.

When glucose is oxidized with nitric acid, it forms saccharide acid. Glucuronic acid, on the other hand, also produces saccharide acid upon oxidation. Therefore, both glucose and glucuronic acid yield the same product, which is saccharide acid.

In fibrous proteins, the polypeptide chains are held together by disulphide linkages. Disulphide linkages are covalent bonds formed between two cysteine amino acids, where the sulfur atoms from each cysteine form a bond. These linkages are strong and stable, contributing to the structural integrity of fibrous proteins such as keratin and collagen. Vander Waal forces are weak intermolecular forces, electrostatic forces of attraction refer to ionic bonds, and none of these options accurately describe the bonding in fibrous proteins.

When a native protein is subjected to physical or chemical treatment that disrupts its conformers, but does not affect its primary structure, it is called a denatured protein. Denaturation refers to the process in which a protein loses its three-dimensional structure and becomes unfolded or disordered. This can be caused by factors such as heat, pH changes, or exposure to certain chemicals. Denatured proteins often lose their biological activity and may no longer function properly.

Amino acids are organic compounds that contain both an amino group (-NH2) and a carboxyl group (-COOH). The presence of the amino group makes the amino acid basic. In basic conditions, the amino group can accept a proton (H+) to form a positively charged amino group (-NH3+). This ability to accept a proton gives amino acids their basic nature. The presence of more amino groups than carbonyl groups in an amino acid further enhances its basicity. Therefore, more amino groups than carbonyl groups in amino acids make them basic.

The helical structure of a protein is stabilized by hydrogen bonds. Hydrogen bonds form between the carbonyl oxygen atom of one amino acid and the amide hydrogen atom of another amino acid, creating a stable interaction that helps maintain the helical shape. These hydrogen bonds occur between the backbone atoms of the protein, specifically between the carbonyl group of one amino acid and the amide group of another amino acid, contributing to the stability and structure of the protein. Ether bonds, peptide bonds, and dipeptide bonds do not play a significant role in stabilizing the helical structure of proteins.

Anomers are a type of stereoisomers that differ in the configuration of the hydroxyl group at the anomeric carbon. In this case, α-D(+) glucose and β-D(+) glucose are anomers because they differ in the orientation of the hydroxyl group attached to the anomeric carbon. The α-anomer has the hydroxyl group pointing downwards, while the β-anomer has it pointing upwards. Anomers are important in carbohydrate chemistry as they can have different properties and reactivity due to their distinct stereochemistry.

Starch is a polymer of α-glucose because it is composed of multiple glucose units linked together through glycosidic bonds. This polymerization of glucose molecules forms a long chain structure, which is characteristic of starch. Starch is a common carbohydrate found in plants and serves as a storage form of energy.

Glucose is a monosaccharide that exists in both pyranose and furanose forms. The pyranose form is more stable and commonly found in glucose molecules. The statement that glucose is present in the furanose form is incorrect because the furanose form is less common in glucose.

The correct answer is α-helical backbone. The secondary structure of a protein refers to the local folding patterns that are formed by hydrogen bonding between the backbone atoms. One common secondary structure is the α-helix, where the backbone forms a spiral shape stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen of an amino acid four residues away. This arrangement allows for efficient packing of the protein and contributes to its overall stability.

A native protein refers to a protein that exists in its natural, functional form within a biological system. It possesses a specific three-dimensional structure, which is crucial for its biological activity. Native proteins are folded correctly and have the appropriate configuration to perform their intended functions. This term distinguishes them from denatured or inactive proteins, which have lost their proper structure and function. Amino acids are the building blocks of proteins, while conformer protein is not a commonly used term in biology.

Glycogen is a polysaccharide that serves as a storage form of glucose in animals. Its structure is similar to amylopectin, which is a branched polysaccharide found in plants. Both glycogen and amylopectin have a highly branched structure, with many glucose units linked together. This branching allows for efficient storage and quick release of glucose when needed. Cellulose, on the other hand, is a structural polysaccharide found in plants and has a linear structure. Amylase is an enzyme that helps break down starch into smaller sugar molecules. Glucose is a monosaccharide and the basic unit of carbohydrates.

Amylopectin is a branched polymer of glucose. It is a type of starch found in plants and serves as a storage form of glucose. Amylopectin has a highly branched structure, with many side chains attached to the main glucose chain. This branching allows for more efficient storage and release of glucose molecules when needed for energy. Amylase, cellulose, and glycogen are also carbohydrates, but they do not have the same branched structure as amylopectin.

The given statement is incorrect because cane sugar actually gives a quimolar mixture of D-(+)-glucose and D-(-)-fructose. A quimolar mixture means that the ratio of glucose to fructose is 1:1.

The correct answer is β-D Glucose and β-D Galactose. Lactose is a disaccharide composed of one molecule of β-D Glucose and one molecule of β-D Galactose.

The segment of DNA that acts as the instructional manual for protein synthesis is called a gene. Genes are specific sequences of DNA that contain the information needed to make a particular protein. They are transcribed into messenger RNA (mRNA), which is then translated into a protein by the ribosomes. Nucleosides and nucleotides are the building blocks of DNA, while ribose is a type of sugar found in RNA.

Mutarotation refers to the spontaneous change in the specific rotation of an optically active compound. This change occurs due to the interconversion between different anomers of the compound in solution. Anomers are isomers that differ in the configuration of the anomeric carbon, which is the carbon atom bonded to both an oxygen atom and the rest of the molecule. Mutarotation is commonly observed in sugars, such as glucose, where the equilibrium between the α and β anomers leads to a change in the specific rotation of the compound.

The correct answer is α-D-Glucopyranose and β-D-fructofuranose. Sucrose is a disaccharide composed of glucose and fructose. α-D-Glucopyranose and β-D-fructofuranose are the correct monosaccharides that form sucrose.

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The assertion states that the β-pleated sheet structure of protein shows maximum extension. The reason given is that intermolecular hydrogen bonding is present in them. While it is true that intermolecular hydrogen bonding is present in β-pleated sheets, this does not necessarily mean that it results in maximum extension. The extension of a protein structure is determined by various factors such as the amino acid sequence and the overall folding pattern. Therefore, the reason is a wrong explanation for the assertion.