Biomolecules

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Learning Objectives

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Explain the characteristics of biomolecules such as carbohydrates, proteins, nucleic acids, and hormones.
Classify carbohydrates, proteins, nucleic acids, and vitamins based on their structures.
Explain the difference between DNA and RNA.
Describe the role of biomolecules in biosystems.

Revision Notes & Summary

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Notes on Biomolecules

10.1 Carbohydrates

Definition: Carbohydrates are optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis.
Classification: Broadly classified into three groups:
- Monosaccharides
- Disaccharides
- Polysaccharides
Examples: Cane sugar, glucose, starch.
General Formula: Cₓ(H₂O)ᵥ (e.g., glucose: C₆H₁₂O₆).
Functions:
- Energy source for mammals (e.g., glucose from starch digestion).
- Storage molecules (starch in plants, glycogen in animals).

10.2 Proteins

Definition: Proteins are polymers of about twenty different α-amino acids linked by peptide bonds.
Essential Amino Acids: Cannot be synthesized by the body; must be obtained from the diet (e.g., Isoleucine, Arginine).
Denaturation: Change in pH or temperature can disturb secondary and tertiary structures, affecting function.
Enzymes: Biocatalysts that speed up reactions; specific to substrates.

10.3 Nucleic Acids

Definition: Polymers of nucleotides, consisting of a base, a pentose sugar, and a phosphate moiety.
Types: DNA and RNA.
- DNA: Contains deoxyribose, double-stranded, includes bases adenine, guanine, cytosine, and thymine.
- RNA: Contains ribose, single-stranded, includes adenine, guanine, cytosine, and uracil.
Functions: Genetic information transfer, protein synthesis.

10.4 Vitamins

Definition: Organic compounds required in small amounts for specific biological functions.
Classification:
- Fat-soluble (A, D, E, K)
- Water-soluble (B group, C)
Importance: Deficiency can lead to diseases.

10.5 Hormones

Definition: Molecules acting as intercellular messengers produced by endocrine glands.
Types: Steroids (e.g., estrogens), polypeptides (e.g., insulin), amino acid derivatives (e.g., epinephrine).
Functions: Regulate biological activities, maintain homeostasis (e.g., insulin regulates blood glucose levels).

10.6 Key Concepts

Glycosidic Linkage: Bond between monosaccharides in carbohydrates.
Peptide Linkage: Bond between amino acids in proteins.
Denaturation: Loss of protein structure and function due to external stress.
Complementary Strands: DNA strands are not identical but complementary, crucial for replication.

Exam Tips & Common Mistakes

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Common Mistakes and Exam Tips

Common Pitfalls

Misclassification of Carbohydrates: Students often confuse monosaccharides with disaccharides. Remember that monosaccharides cannot be hydrolyzed further, while disaccharides can yield two monosaccharide units upon hydrolysis.
Glycosidic Linkage Confusion: Misunderstanding the term glycosidic linkage can lead to incorrect answers. Ensure you know it refers to the bond formed between monosaccharides.
Denaturation Effects: Students may overlook that denaturation affects secondary and tertiary structures of proteins but leaves the primary structure intact.
Vitamins Classification: Confusion between fat-soluble and water-soluble vitamins is common. Remember that fat-soluble vitamins (A, D, E, K) can be stored in the body, while water-soluble vitamins (B group and C) cannot.

Exam Tips

Understand Definitions: Be clear on definitions such as monosaccharides, disaccharides, and glycosidic linkages. Write them out if necessary.
Practice Classification: Regularly practice classifying carbohydrates and amino acids to avoid mistakes during exams.
Memorize Key Differences: Focus on the structural differences between DNA and RNA, as well as the functions of different types of RNA.
Use Diagrams: If applicable, draw diagrams to illustrate concepts like the structure of DNA or the process of denaturation to reinforce your understanding.
Review Functions of Biomolecules: Make sure you can list and explain the functions of carbohydrates, proteins, and nucleic acids, as these are often exam topics.

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Practice Test – MCQs, True/False

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Multiple Choice Questions

It alters the primary structure of proteins.

It causes the proteins to become more soluble in water.

It disrupts the secondary and tertiary structures, but not the primary structure.

It enhances the enzymatic activity of proteins.

Correct Answer: C

Solution:

Denaturation affects the secondary and tertiary structures of proteins, leading to loss of function, but the primary structure remains intact.

Vitamin A

Vitamin C

Vitamin E

Vitamin K

Correct Answer: D

Solution:

Vitamin K is responsible for blood coagulation, and its deficiency increases blood clotting time.

DNA contains a five-carbon sugar molecule called ribose, while RNA contains 2-deoxyribose.

Both DNA and RNA contain the sugar ribose.

DNA contains a five-carbon sugar molecule called 2-deoxyribose, while RNA contains ribose.

Both DNA and RNA contain the sugar 2-deoxyribose.

Correct Answer: C

Solution:

DNA contains a five-carbon sugar molecule called 2-deoxyribose, while RNA contains ribose.

DNA contains ribose sugar, while RNA contains deoxyribose.

DNA is single-stranded, while RNA is double-stranded.

DNA contains thymine, while RNA contains uracil.

DNA is found only in the cytoplasm, while RNA is found only in the nucleus.

Correct Answer: C

Solution:

DNA contains thymine as a base, whereas RNA contains uracil instead of thymine.

Ionic bonds

Hydrogen bonds

Disulfide bonds

Covalent bonds

Correct Answer: B

Solution:

Hydrogen bonds help in stabilizing the α-helix structure of proteins.

They store energy in the form of ATP.

They form the structural components of cell membranes.

They carry genetic information and are involved in protein synthesis.

They act as enzymes in metabolic reactions.

Correct Answer: C

Solution:

Nucleic acids like DNA and RNA carry genetic information and are involved in protein synthesis.

Starch

Cellulose

Glycogen

Sucrose

Correct Answer: C

Solution:

Glycogen is the main storage polysaccharide in animals, similar to starch in plants.

The rate of sucrose hydrolysis will increase.

The rate of sucrose hydrolysis will decrease.

The enzyme will become more specific to its substrate.

The enzyme will start catalyzing a different reaction.

Correct Answer: B

Solution:

Enzymes reduce the activation energy required for a reaction. If sucrase loses this ability, the rate of sucrose hydrolysis will decrease as the reaction will require more energy to proceed.

Enzymes are consumed in the reactions they catalyze.

Enzymes increase the activation energy required for reactions.

Enzymes provide an alternative reaction pathway with lower activation energy.

Enzymes are only involved in catabolic reactions.

Correct Answer: C

Solution:

Enzymes act as catalysts by providing an alternative reaction pathway that lowers the activation energy, thus speeding up the reaction.

Amylose is branched, amylopectin is unbranched

Amylose is unbranched, amylopectin is branched

Amylose contains β-glucose, amylopectin contains α-glucose

Amylose is a protein, amylopectin is a carbohydrate

Correct Answer: B

Solution:

Amylose is a long unbranched chain, while amylopectin is a branched chain polymer.

Glucose

Fructose

Sucrose

Ribose

Correct Answer: C

Solution:

Sucrose is a disaccharide composed of glucose and fructose.

DNA contains uracil, while RNA contains thymine.

DNA is a double-stranded molecule, while RNA is single-stranded.

DNA contains ribose sugar, while RNA contains deoxyribose sugar.

DNA is found only in the cytoplasm, while RNA is found in the nucleus.

Correct Answer: B

Solution:

DNA is a double-stranded molecule, whereas RNA is typically single-stranded.

Cellulose

Starch

Glycogen

Sucrose

Correct Answer: B

Solution:

Starch is a polymer of α-glucose, consisting of amylose and amylopectin.

Starch is a polymer of α-glucose, while cellulose is a polymer of β-glucose.

Starch is a linear polymer, while cellulose is branched.

Starch is used for structural support, while cellulose is used for energy storage.

Starch contains β-linkages, while cellulose contains α-linkages.

Correct Answer: A

Solution:

Starch is composed of α-glucose units, while cellulose is composed of β-glucose units, which affects their respective structures and functions.

Increased blood glucose levels.

Decreased digestion of starch.

Accumulation of sucrose in the digestive tract.

Enhanced absorption of fructose.

Correct Answer: C

Solution:

Inhibition of sucrase would prevent the hydrolysis of sucrose into glucose and fructose, leading to the accumulation of sucrose in the digestive tract.

Increased production of glucose and galactose.

Decreased rate of lactose hydrolysis.

No effect on the rate of lactose hydrolysis.

Conversion of lactose into sucrose.

Correct Answer: B

Solution:

An enzyme inhibitor would decrease the rate of lactose hydrolysis by interfering with the enzyme's ability to catalyze the reaction.

Amylose is a branched polymer, whereas amylopectin is a linear polymer.

Amylose is a linear polymer, whereas amylopectin is a branched polymer.

Both amylose and amylopectin are branched polymers.

Both amylose and amylopectin are linear polymers.

Correct Answer: B

Solution:

Amylose is a long, unbranched chain of α-D-glucose units connected by C1-C4 glycosidic linkages, while amylopectin is a branched polymer with C1-C4 and C1-C6 glycosidic linkages.

α-linkage

β-linkage

Peptide linkage

Ionic bond

Correct Answer: B

Solution:

Cellulose is composed of β-D-glucose units linked by β-linkages.

Glycogen

Cellulose

Starch

Sucrose

Correct Answer: C

Solution:

Starch is the main storage polysaccharide in plants.

Ribose

Maltose

Lactose

Sucrose

Correct Answer: A

Solution:

Ribose is a monosaccharide, while maltose, lactose, and sucrose are disaccharides.

RNA with base X will not be able to participate in protein synthesis.

RNA with base X will still be able to form a double helix with DNA.

RNA with base X will have a different tertiary structure due to altered base pairing.

RNA with base X will not affect the stability of the RNA molecule.

Correct Answer: C

Solution:

The presence of base X, which forms a stable pair with adenine, suggests that the RNA may have a different tertiary structure due to altered base pairing. This can affect how the RNA folds and interacts with other molecules.

Oxidoreductase

Hydrolase

Ligase

Isomerase

Correct Answer: B

Solution:

Hydrolases are enzymes that catalyze the hydrolysis of chemical bonds, including the breakdown of disaccharides into monosaccharides.

It is a linear polymer of beta-D-glucose units.

It is a highly branched polymer of alpha-D-glucose units.

It is composed of ribose and deoxyribose sugars.

It is a component of the cell wall in plants.

Correct Answer: B

Solution:

Glycogen is a highly branched polymer of alpha-D-glucose units. It serves as a storage form of glucose in animals, similar to amylopectin in plants.

XNA will form a double helix similar to DNA.

XNA will be more stable than RNA due to the extra hydroxyl group.

XNA will likely be less stable than RNA due to the additional hydroxyl group.

XNA will not be involved in protein synthesis.

Correct Answer: C

Solution:

The additional hydroxyl group at the 3' position makes XNA more reactive and less stable than RNA, which already has a hydroxyl group at the 2' position.

Sucrose

Maltose

Lactose

Fructose

Correct Answer: C

Solution:

Lactose is a disaccharide composed of glucose and galactose. It is commonly found in milk.

Contains thymine

Double-stranded

Contains uracil

Contains 2-deoxyribose

Correct Answer: C

Solution:

RNA contains uracil instead of thymine, which is found in DNA.

α-1,4-glycosidic linkage

β-1,4-glycosidic linkage

α-1,6-glycosidic linkage

β-1,6-glycosidic linkage

Correct Answer: C

Solution:

Glycogen is a highly branched polysaccharide, and the branching is due to α-1,6-glycosidic linkages. The main chain of glycogen is formed by α-1,4-glycosidic linkages.

DNA

RNA

tRNA

mRNA

Correct Answer: B

Solution:

RNA contains ribose, a pentose sugar with an additional hydroxyl group compared to the deoxyribose in DNA. This additional hydroxyl group is present at the 2' position in ribose.

Storing genetic information for protein synthesis.

Acting as enzymes to catalyze biochemical reactions.

Transmitting hereditary information from one generation to the next.

Providing structural support to cells.

Correct Answer: B

Solution:

Nucleic acids primarily store genetic information and transmit hereditary information. They do not act as enzymes; proteins typically fulfill enzymatic roles.

Energy storage

Protein synthesis

DNA replication

Hormone production

Correct Answer: A

Solution:

Carbohydrates in plants primarily function as energy storage molecules, such as starch.

Vitamin A

Vitamin D

Vitamin E

Vitamin C

Correct Answer: D

Solution:

Vitamin C is a water-soluble vitamin, while vitamins A, D, and E are fat-soluble.

It is more soluble in water than amylopectin.

It has a higher energy storage capacity than amylopectin.

It is less digestible by human enzymes compared to amylopectin.

It forms a more rigid structure than cellulose.

Correct Answer: B

Solution:

The additional branching points increase the number of terminal glucose units, enhancing the energy storage capacity of the polysaccharide.

DNA contains the sugar 2-deoxyribose, while RNA contains ribose.

Both DNA and RNA contain the bases adenine, guanine, and cytosine.

Thymine is found in RNA, whereas uracil is found in DNA.

DNA is typically double-stranded, whereas RNA is typically single-stranded.

Correct Answer: C

Solution:

Thymine is found in DNA, while uracil is found in RNA. This makes option C incorrect.

Adenine

Guanine

Thymine

Uracil

Correct Answer: D

Solution:

Uracil is found in RNA, whereas thymine is found in DNA.

Hydrolysis

Denaturation

Saponification

Polymerization

Correct Answer: B

Solution:

Denaturation involves the disruption of secondary and tertiary structures of proteins due to external stress like heat, while the primary structure remains unchanged.

mRNA

tRNA

rRNA

snRNA

Correct Answer: B

Solution:

tRNA (transfer RNA) is responsible for carrying amino acids to the ribosome for protein synthesis.

The DNA will become more stable due to increased ionic interactions.

The DNA will lose its ability to form a double helix.

The DNA will have increased resistance to enzymatic degradation.

The DNA will have enhanced binding affinity to proteins.

Correct Answer: B

Solution:

Replacing the phosphate group with a sulfate group would disrupt the normal backbone structure of DNA, preventing the formation of the double helix.

DNA is involved in protein synthesis, while RNA stores genetic information.

DNA is double-stranded and primarily stores genetic information, while RNA is single-stranded and involved in protein synthesis.

DNA contains uracil, while RNA contains thymine.

DNA is found only in the nucleus, while RNA is found only in the cytoplasm.

Correct Answer: B

Solution:

DNA is a double-stranded molecule that stores genetic information, whereas RNA is single-stranded and plays a direct role in protein synthesis.

Vitamin A

Vitamin C

Vitamin D

Vitamin K

Correct Answer: D

Solution:

Vitamin K is known for its role in blood coagulation. A compound whose deficiency leads to delayed blood clotting would most closely resemble Vitamin K in function.

Cellulose

Starch

Glycogen

Sucrose

Correct Answer: A

Solution:

Cellulose is a polysaccharide that forms the structural component of the plant cell wall.

Starch is a polymer of ß-glucose, cellulose is a polymer of α-glucose.

Starch is a polymer of α-glucose, cellulose is a polymer of ß-glucose.

Starch is a polymer of ribose, cellulose is a polymer of deoxyribose.

Starch is a polymer of nucleotides, cellulose is a polymer of amino acids.

Correct Answer: B

Solution:

Starch is a polymer of α-glucose, whereas cellulose is a polymer of ß-glucose.

Omega-glucan will form a linear chain without branching.

Omega-glucan will form a highly branched structure.

Omega-glucan will be a cyclic polysaccharide.

Omega-glucan will not be able to form hydrogen bonds.

Correct Answer: A

Solution:

The C1-C5 glycosidic bonds suggest a linear chain structure without branching, as branching typically involves C1-C6 linkages.

Fat-soluble vitamins

Water-soluble vitamins

Minerals

Amino acids

Correct Answer: B

Solution:

Water-soluble vitamins, such as vitamin C and the B vitamins, are not stored in the body and need to be consumed regularly to prevent deficiency.

It is composed of α-D-glucose units.

It is a storage polysaccharide in animals.

It is a straight chain polysaccharide composed of β-D-glucose units.

It is soluble in water.

Correct Answer: C

Solution:

Cellulose is a straight chain polysaccharide composed of β-D-glucose units, which are linked by glycosidic bonds between C1 of one glucose and C4 of the next glucose unit.

Sucrose

Lactose

Starch

Cellulose

Correct Answer: B

Solution:

Lactose is a reducing sugar because it has a free aldehyde group that can reduce other substances.

Glucose

Fructose

Lactose

Maltose

Correct Answer: C

Solution:

Lactose is the disaccharide sugar found in milk, composed of ß-D-galactose and ß-D-glucose.

Vitamin A

Vitamin C

Vitamin E

Vitamin K

Correct Answer: D

Solution:

Vitamin K is responsible for the coagulation of blood.

It forms a straight chain similar to cellulose.

It forms a helical structure similar to amylose.

It forms a highly branched structure similar to glycogen.

It forms a gel-like structure in water.

Correct Answer: A

Solution:

The β-D-glucose units linked by C1-C3 glycosidic bonds suggest a linear arrangement, similar to cellulose, which is composed of β-D-glucose units linked by C1-C4 bonds.

Ionic bonding

Hydrogen bonding

Covalent bonding

Van der Waals forces

Correct Answer: B

Solution:

Hydrogen bonding is the primary force that stabilizes the α-helix structure in proteins.

The mutation will have no effect on DNA replication.

The mutation will cause the DNA to replicate faster.

The mutation will disrupt the complementary base pairing, leading to errors in replication.

The mutation will enhance the stability of the DNA double helix.

Correct Answer: C

Solution:

Replacing thymine with a non-standard base disrupts the specific hydrogen bonding required for accurate base pairing, leading to replication errors.

Starch

Cellulose

Glycogen

Amylose

Correct Answer: C

Solution:

Glycogen is the polysaccharide stored in animals, particularly in the liver and muscles. It is highly branched, similar to amylopectin in plants, but more extensively.

DNA contains the sugar ribose, while RNA contains the sugar deoxyribose.

DNA is a single-stranded molecule, while RNA is a double-stranded molecule.

DNA contains thymine, while RNA contains uracil.

DNA is composed of adenine, guanine, cytosine, and uracil, while RNA is composed of adenine, guanine, cytosine, and thymine.

Correct Answer: C

Solution:

DNA contains the base thymine, whereas RNA contains uracil instead of thymine. DNA is double-stranded, and RNA is single-stranded. The sugar in DNA is deoxyribose, while RNA contains ribose.

2-deoxyribose

Ribose

Fructose

Glucose

Correct Answer: B

Solution:

RNA contains ribose, a five-carbon sugar.

It serves as a structural component.

It acts as a storage form of glucose.

It is involved in protein synthesis.

It is a component of cell membranes.

Correct Answer: B

Solution:

Glycogen acts as a storage form of glucose in animals, similar to starch in plants.

Enzymes increase the activation energy required for reactions.

Enzymes decrease the activation energy required for reactions.

Enzymes are consumed in the reactions they catalyze.

Enzymes change the equilibrium position of reactions.

Correct Answer: B

Solution:

Enzymes act as catalysts by decreasing the activation energy required for reactions, thereby increasing the rate of reaction without being consumed.

Solubility in water

Thermal stability

Flexibility

Enzymatic activity

Correct Answer: B

Solution:

Disulfide bonds contribute to the stability of a protein's tertiary structure, making it more resistant to denaturation by heat, thus enhancing thermal stability.

Vitamin A

Vitamin C

Vitamin D

Vitamin E

Correct Answer: B

Solution:

Vitamin C is a water-soluble vitamin essential for collagen synthesis and other functions in the body.

Ribose

Glucose

2-deoxyribose

Fructose

Correct Answer: C

Solution:

DNA contains a five carbon sugar molecule called 2-deoxyribose.

Increased flexibility and elasticity.

Decreased resistance to microbial attack.

Enhanced structural integrity.

Improved water retention capacity.

Correct Answer: B

Solution:

The substitution of ß-D-galactose for ß-D-glucose would likely disrupt the regular structure of cellulose, making the cell wall more susceptible to microbial degradation.

mRNA

tRNA

rRNA

cRNA

Correct Answer: D

Solution:

The three types of RNA are mRNA, tRNA, and rRNA. cRNA is not a recognized type.

Enzymes are primarily composed of lipids.

Enzymes are non-specific catalysts.

Enzymes speed up reactions by lowering activation energy.

Enzymes are used up in chemical reactions.

Correct Answer: C

Solution:

Enzymes speed up reactions by lowering the activation energy, allowing reactions to occur under milder conditions.

Monosaccharide

Disaccharide

Polysaccharide

Oligosaccharide

Correct Answer: A

Solution:

Ribose is classified as a monosaccharide, which is a simple sugar.

To carry amino acids to the ribosome.

To form the structure of ribosomes.

To carry the genetic code from DNA to the ribosome.

To catalyze the formation of peptide bonds.

Correct Answer: C

Solution:

mRNA carries the genetic code from DNA to the ribosome for protein synthesis.

To carry amino acids to the ribosome

To form the structure of ribosomes

To carry the genetic code from DNA to the ribosome

To catalyze the formation of peptide bonds

Correct Answer: C

Solution:

mRNA, or messenger RNA, carries the genetic information transcribed from DNA in the form of codons to the ribosome, where protein synthesis occurs.

They act as structural components

They serve as energy storage

They catalyze biochemical reactions

They transmit genetic information

Correct Answer: C

Solution:

Enzymes are biocatalysts that speed up biochemical reactions in living organisms.

They are polymers of amino acids.

They are responsible for the transfer of characters from parents to offspring.

They are primarily involved in the digestion of food.

They are composed of lipids and proteins.

Correct Answer: B

Solution:

Nucleic acids are responsible for the transfer of characters from parents to offspring, as they contain the genetic information.

Amylose is a linear polymer, while amylopectin is a branched polymer.

Amylose is composed of β-D-glucose units, while amylopectin is composed of α-D-glucose units.

Amylose is water-insoluble, while amylopectin is water-soluble.

Amylose contains C1-C6 glycosidic linkages, while amylopectin contains C1-C4 glycosidic linkages.

Correct Answer: A

Solution:

Amylose is a linear polymer of α-D-glucose units linked by C1-C4 glycosidic bonds, while amylopectin is a branched polymer with both C1-C4 and C1-C6 linkages.

C1-C2 glycosidic linkage

C1-C4 glycosidic linkage

C1-C6 glycosidic linkage

Peptide linkage

Correct Answer: B

Solution:

Amylose is a polymer of α-D-(+)-glucose units connected by C1-C4 glycosidic linkages.

Sucrose

Lactose

Maltose

Fructose

Correct Answer: B

Solution:

Lactose is a disaccharide composed of ß-D-galactose and ß-D-glucose, commonly found in milk.

Vitamin A

Vitamin C

Vitamin E

Vitamin K

Correct Answer: D

Solution:

Vitamin K is essential for the synthesis of proteins that mediate blood coagulation.

Primary structure

Secondary structure

Tertiary structure

Quaternary structure

Correct Answer: A

Solution:

Denaturation affects the secondary, tertiary, and quaternary structures of proteins, but the primary structure, which is the sequence of amino acids, remains intact.

Glucose and fructose

Glucose and galactose

Glucose and sucrose

Glucose and maltose

Correct Answer: B

Solution:

Lactose hydrolyzes into glucose and galactose.

Vitamin B

Vitamin C

Vitamin D

Vitamin K

Correct Answer: C

Solution:

Vitamin D is a fat-soluble vitamin, along with vitamins A, E, and K.

Starch

Cellulose

Glycogen

Sucrose

Correct Answer: C

Solution:

Glycogen is the primary storage form of carbohydrates in animals, similar to amylopectin but more highly branched.

α-1,4-glycosidic linkage

α-1,6-glycosidic linkage

ß-1,4-glycosidic linkage

ß-1,6-glycosidic linkage

Correct Answer: C

Solution:

Cellulose is composed of ß-D-glucose units joined by ß-1,4-glycosidic linkages.

Vitamin A

Vitamin C

Vitamin D

Vitamin K

Correct Answer: D

Solution:

Vitamin K is essential for the synthesis of proteins required for blood coagulation.

True or False

Correct Answer: False

Solution:

The sugar present in DNA is 2-deoxyribose, not ribose.

Correct Answer: True

Solution:

DNA is structured as a double helix, as discovered by Watson and Crick.

Correct Answer: True

Solution:

DNA is the chemical basis of heredity and is responsible for storing and transmitting genetic information.

Correct Answer: True

Solution:

Enzymes are highly specific and selective, meaning they typically catalyze only one type of reaction or act on a specific substrate.

Correct Answer: False

Solution:

The sugar present in RNA is ribose, not 2-deoxyribose which is found in DNA.

Correct Answer: False

Solution:

DNA contains thymine, whereas RNA contains uracil instead of thymine.

Correct Answer: False

Solution:

Enzymes are primarily composed of proteins, not carbohydrates.

Correct Answer: False

Solution:

The two strands in DNA are not identical but are complementary.

Correct Answer: False

Solution:

The sugar present in DNA is 2-deoxyribose, not ribose. Ribose is found in RNA.

Correct Answer: False

Solution:

DNA contains the sugar 2-deoxyribose, not ribose.

Correct Answer: True

Solution:

DNA holds the genetic blueprint for the synthesis of proteins, which are essential for cellular functions.

Correct Answer: False

Solution:

During denaturation, the secondary and tertiary structures are destroyed, but the primary structure remains intact.

Correct Answer: True

Solution:

Enzymes are indeed proteins that function as biocatalysts, facilitating and accelerating biochemical reactions.

Correct Answer: True

Solution:

Nucleic acids, such as DNA, are responsible for the transmission of genetic information from one generation to the next.

Correct Answer: False

Solution:

DNA contains the sugar 2-deoxyribose, not ribose. Ribose is found in RNA.

Correct Answer: True

Solution:

Nucleic acids, such as DNA and RNA, are indeed polymers of nucleotides and play a crucial role in heredity by transferring genetic information.

Correct Answer: False

Solution:

DNA contains a five-carbon sugar molecule called 2-deoxyribose, not ribose.

Correct Answer: False

Solution:

Starch is a storage polysaccharide found in plants, whereas glycogen serves a similar function in animals.

Correct Answer: True

Solution:

Glycogen is known as animal starch and is more highly branched than amylopectin, which is a component of starch.

Correct Answer: False

Solution:

Cellulose is a straight chain polysaccharide composed of

\beta

-D-glucose units.

Correct Answer: False

Solution:

Glycogen is the storage form of carbohydrates in animals, while starch is the storage form in plants.

Correct Answer: True

Solution:

Cellulose is a polysaccharide composed only of ß-D-glucose units, which are joined by glycosidic linkages.

Correct Answer: False

Solution:

Enzymes are primarily composed of proteins, not lipids. They are biocatalysts that speed up reactions in biosystems.

Correct Answer: True

Solution:

The three main types of RNA that play roles in protein synthesis are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).

Correct Answer: True

Solution:

DNA is known for its double helix structure, while RNA is usually single-stranded.

Correct Answer: False

Solution:

DNA contains the sugar 2-deoxyribose, whereas RNA contains ribose.

Correct Answer: False

Solution:

Lactose is a disaccharide composed of ß-D-galactose and ß-D-glucose, not glucose and fructose.

Correct Answer: False

Solution:

The fourth base in RNA is uracil, not thymine. Thymine is found in DNA.

Correct Answer: True

Solution:

Nucleic acids, such as DNA and RNA, are indeed polymers of nucleotides, each comprising a nitrogenous base, a pentose sugar, and a phosphate group.

Correct Answer: True

Solution:

Lactose is indeed composed of ß-D-galactose and ß-D-glucose, linked between C1 of galactose and C4 of glucose.

Correct Answer: True

Solution:

Both DNA and RNA contain the bases adenine, guanine, and cytosine. The difference lies in the fourth base: DNA contains thymine, while RNA contains uracil.

Correct Answer: False

Solution:

Glycogen is the storage form of carbohydrates in animals, not plants.

Correct Answer: True

Solution:

Cellulose is a straight chain polysaccharide composed of ß-D-glucose units linked by ß-glycosidic bonds between C1 of one glucose unit and C4 of the next.

Correct Answer: False

Solution:

Glycogen is a storage polysaccharide found in animals, not plants. It is known as animal starch.

Correct Answer: True

Solution:

Cellulose is indeed a straight chain polysaccharide composed of ß-D-glucose units joined by glycosidic linkages.

Correct Answer: True

Solution:

Enzymes are proteins that act as catalysts to accelerate biochemical reactions in living organisms.

Correct Answer: False

Solution:

The two strands in DNA are not identical but are complementary.

Correct Answer: True

Solution:

The three types of RNA involved in protein synthesis are mRNA, rRNA, and tRNA.

Correct Answer: False

Solution:

DNA is a double-stranded molecule, whereas RNA is typically single-stranded.

Correct Answer: True

Solution:

Glycogen is known as animal starch because its structure is similar to amylopectin and is highly branched.

Correct Answer: False

Solution:

Glycogen is a storage polysaccharide found in animals, not plants. Starch is the main storage polysaccharide in plants.

Correct Answer: False

Solution:

DNA contains thymine, while RNA contains uracil instead of thymine.

Correct Answer: True

Solution:

Starch is indeed the main storage polysaccharide in plants.

Correct Answer: True

Solution:

Nucleic acids, such as DNA and RNA, carry genetic information that is passed from one generation to the next.

Correct Answer: False

Solution:

RNA is a single-stranded molecule, whereas DNA is double-stranded.

Correct Answer: True

Solution:

Cellulose is indeed composed of

\beta

-D-glucose units linked by glycosidic bonds.

Correct Answer: True

Solution:

Nucleic acids, such as DNA and RNA, carry genetic information that is passed from parents to offspring, ensuring the transfer of hereditary traits.

Correct Answer: True

Solution:

Glycogen is similar to amylopectin but is more highly branched.

Correct Answer: False

Solution:

DNA contains the sugar 2-deoxyribose, whereas RNA contains ribose.

Correct Answer: True

Solution:

Cellulose is a polysaccharide composed of ß-D-glucose units joined by glycosidic linkages.

Correct Answer: False

Solution:

DNA contains 2-deoxyribose, while RNA contains ribose.

Correct Answer: True

Solution:

Vitamins are classified into two categories: fat-soluble (A, D, E, and K) and water-soluble (B group and C).

Correct Answer: True

Solution:

Enzymes are primarily proteins that speed up chemical reactions in biological systems.

Correct Answer: False

Solution:

DNA is composed of a double strand, and RNA is composed of a single strand.

Correct Answer: False

Solution:

DNA contains the sugar 2-deoxyribose, whereas RNA contains ribose.

Correct Answer: True

Solution:

Glycogen is a storage polysaccharide found in animals, similar in structure to amylopectin but more highly branched.

Correct Answer: False

Solution:

During denaturation, the secondary and tertiary structures are destroyed, but the primary structure remains intact.

Correct Answer: False

Solution:

Enzymes are very specific for a particular reaction and for a particular substrate.

Correct Answer: False

Solution:

RNA contains ribose as its sugar, whereas DNA contains 2-deoxyribose.

Correct Answer: True

Solution:

Proteins are indeed polymers made up of amino acids, which are linked together by peptide bonds.

Correct Answer: False

Solution:

Glycogen is found in animals and is more highly branched than amylopectin.

Correct Answer: False

Solution:

Glycogen is the main storage polysaccharide in animals, while starch is the main storage polysaccharide in plants.

Correct Answer: False

Solution:

The sugar in RNA is ß-D-ribose, while DNA contains ß-D-2-deoxyribose.

Correct Answer: False

Solution:

Proteins are polymers of

\alpha

-amino acids, not nucleotides.

Correct Answer: False

Solution:

Cellulose is a straight chain polysaccharide composed of

\beta

-D-glucose units.

Correct Answer: True

Solution:

Nucleic acids are indeed polymers of nucleotides, which consist of a base, a pentose sugar, and a phosphate moiety.

Correct Answer: True

Solution:

Maltase is the enzyme that catalyzes the hydrolysis of maltose into two glucose molecules.

Biomolecules

Learning Objectives

Revision Notes & Summary

Notes on Biomolecules

10.1 Carbohydrates

10.2 Proteins

10.3 Nucleic Acids

10.4 Vitamins

10.5 Hormones

10.6 Key Concepts

Exam Tips & Common Mistakes

Common Mistakes and Exam Tips

Common Pitfalls

Exam Tips

AI Learning Assistant

Practice Test – MCQs, True/False

Multiple Choice Questions

Q1.What is the consequence of the denaturation of proteins?

Correct Answer: C

Q2.Which vitamin is known for increasing blood clotting time when deficient?

Correct Answer: D

Q3.In the context of nucleic acids, which of the following is a correct statement about the sugar component in DNA and RNA?

Correct Answer: C

Q4.What is the primary structural difference between DNA and RNA?

Correct Answer: C

Q5.Which type of bond stabilizes the α-helix structure of proteins?

Correct Answer: B

Q6.Which of the following is a function of nucleic acids?

Correct Answer: C

Q7.What is the main storage polysaccharide in animals?

Correct Answer: C

Q8.In a hypothetical experiment, a mutation causes the enzyme sucrase to lose its ability to reduce activation energy. What is the most likely consequence of this mutation?

Correct Answer: B

Q9.Which of the following statements correctly describes the role of enzymes in biological systems?

Correct Answer: C

Q10.What is the main structural difference between amylose and amylopectin?

Correct Answer: B

Q11.Which of the following is a disaccharide?

Correct Answer: C

Q12.Which of the following is a structural difference between DNA and RNA?

Correct Answer: B

Q13.Which of the following is a polymer of α-glucose?

Correct Answer: B

Q14.What is the primary structural difference between starch and cellulose?

Correct Answer: A

Q15.An experimental drug is designed to inhibit the enzyme sucrase. Which of the following physiological effects is most likely to be observed?

Correct Answer: C

Q16.A researcher is studying the effects of a novel enzyme inhibitor on the hydrolysis of lactose. Which of the following is the most likely result of introducing this inhibitor?

Correct Answer: B

Q17.Which of the following statements correctly describes the structural difference between amylose and amylopectin?

Correct Answer: B

Q18.What type of linkage connects glucose units in cellulose?

Correct Answer: B

Q19.What is the main storage polysaccharide in plants?

Correct Answer: C

Q20.Which of the following is a monosaccharide?

Correct Answer: A

Q21.Consider a scenario where a scientist is experimenting with a new type of RNA that contains an unusual base, X, instead of uracil. This base X forms a stable pair with adenine. Which of the following statements is most likely true about this RNA?

Correct Answer: C

Q22.A newly discovered enzyme catalyzes the conversion of a disaccharide into two monosaccharides. The enzyme is most likely similar to which of the following?

Correct Answer: B

Q23.Which of the following is a characteristic feature of glycogen?

Correct Answer: B

Q24.In a hypothetical scenario, a newly discovered nucleic acid, XNA, is found to contain a sugar molecule similar to ribose but with an additional hydroxyl group at the 3' position. Which of the following statements is most likely true about XNA?

Correct Answer: C

Q25.In a laboratory experiment, a student hydrolyzes a disaccharide and identifies the products as glucose and galactose. Which disaccharide was most likely hydrolyzed?

Correct Answer: C

Q26.Which of the following is a characteristic of RNA but not DNA?

Correct Answer: C

Q27.Which type of glycosidic linkage is primarily responsible for the branching in glycogen?

Correct Answer: C

Q28.In a hypothetical experiment, a scientist isolates a new type of nucleic acid from a microorganism. This nucleic acid contains a pentose sugar with an additional hydroxyl group compared to DNA. Which of the following is most likely the type of nucleic acid discovered?

Correct Answer: B

Q29.Which of the following is NOT a function of nucleic acids?

Correct Answer: B

Q30.Which of the following is a primary function of carbohydrates in plants?

Correct Answer: A

Q31.Which of the following vitamins is classified as water-soluble?

Correct Answer: D

Q32.A researcher is studying a new polysaccharide that is similar to amylopectin but has an additional branching point at every tenth glucose unit. Which of the following statements is most likely true about this polysaccharide?