- 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.
Biomolecules
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TopNotes 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.
Practice Test – MCQs, True/False
TopMultiple Choice Questions
A.
Vitamin E
B.
Vitamin K
C.
Vitamin D
D.
Vitamin B₆
Correct Answer: B
Solution:
Vitamin K is essential for the synthesis of proteins required for blood clotting, and its deficiency increases clotting time.
Chapter Concept:
Vitamins: Classification, Sources and Deficiency Diseases
A.
Vitamin A
B.
Vitamin B₁
C.
Vitamin C
D.
Vitamin D
Correct Answer: A
Solution:
Vitamin A deficiency leads to xerophthalmia, which is the hardening of the cornea, and night blindness.
Chapter Concept:
Vitamins: Classification, Sources and Deficiency Diseases
A.
Glycosidic linkage
B.
Peptide linkage
C.
Phosphodiester linkage
D.
Hydrogen bond
Correct Answer: B
Solution:
A peptide linkage, also known as an amide bond, is formed between the carboxyl group of one amino acid and the amino group of another.
Chapter Concept:
Peptide Linkage and Polypeptides
A.
Two molecules of glucose
B.
One molecule of glucose and one molecule of fructose
C.
Two molecules of fructose
D.
One molecule of galactose and one molecule of glucose
Correct Answer: B
Solution:
Hydrolysis of sucrose yields an equimolar mixture of D-(+)-glucose and D-(-)-fructose.
Chapter Concept:
Glycosidic Linkage and Disaccharides
A.
Lactose is a non-reducing sugar composed of -D-glucose and -D-fructose.
B.
Lactose is a reducing sugar composed of -D-galactose and -D-glucose linked through C1–C4.
C.
Lactose is a reducing sugar composed of -D-glucose and -D-fructose linked through C1–C2.
D.
Lactose is a non-reducing sugar composed of -D-galactose and -D-glucose linked through C1–C4.
Correct Answer: B
Solution:
Lactose is a reducing sugar composed of -D-galactose and -D-glucose linked through C1–C4, allowing a free aldehyde group to form.
Chapter Concept:
Glycosidic Linkage and Disaccharides
A.
DNA is responsible for the synthesis of carbohydrates in the cell.
B.
DNA carries the genetic information necessary for protein synthesis.
C.
DNA acts as a catalyst in biochemical reactions.
D.
DNA is involved in the direct synthesis of lipids.
Correct Answer: B
Solution:
DNA contains the genetic information that directs the synthesis of proteins through various RNA molecules. It does not directly synthesize carbohydrates or lipids, nor does it act as a catalyst.
Chapter Concept:
DNA Fingerprinting and Biological Functions of Nucleic Acids
A.
Amylase
B.
Sucrase
C.
Maltase
D.
Lactase
Correct Answer: B
Solution:
Sucrase is the enzyme that catalyzes the hydrolysis of sucrose into glucose and fructose, reducing the activation energy required for the reaction.
Chapter Concept:
Enzyme Catalysis and Mechanism
A.
-D-2-deoxyribose
B.
-D-ribose
C.
Glucose
D.
Fructose
Correct Answer: B
Solution:
RNA contains -D-ribose as its sugar component, whereas DNA contains -D-2-deoxyribose.
Chapter Concept:
Nucleic Acid Structure and Function
A.
Primary structure
B.
Secondary structure
C.
Tertiary structure
D.
Both secondary and tertiary structures
Correct Answer: D
Solution:
Denaturation affects the secondary and tertiary structures of proteins, leaving the primary structure intact.
Chapter Concept:
Protein Structure and Denaturation
A.
DNA contains the sugar -D-2-deoxyribose, whereas RNA contains -D-ribose.
B.
RNA contains thymine, whereas DNA contains uracil.
C.
DNA is single-stranded, while RNA is double-stranded.
D.
RNA contains a phosphate backbone, while DNA does not.
Correct Answer: A
Solution:
DNA contains -D-2-deoxyribose and bases A, G, C, T, while RNA contains -D-ribose and bases A, G, C, U.
Chapter Concept:
Nucleic Acid Structure and Function
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Biomolecules
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Locked • AI Weakness TrackerTrue or False
Correct Answer: False
Solution:
Sucrose is a non-reducing sugar because the reducing groups of glucose and fructose are involved in glycosidic bond formation, preventing them from being free.
Chapter Concept :
Glycosidic Linkage and Disaccharides
Correct Answer: True
Solution:
Thyroxine is indeed an iodinated derivative of tyrosine. A deficiency in thyroxine, often due to low iodine intake, can lead to hypothyroidism, characterized by symptoms such as lethargy and obesity.
Chapter Concept :
Hormonal Regulation and Function
Correct Answer: False
Solution:
The statement is false. RNA contains the sugar ribose, while DNA contains the sugar 2-deoxyribose.
Chapter Concept :
DNA vs RNA
Correct Answer: True
Solution:
Glycogen is similar to amylopectin but is more highly branched, which makes it an effective storage form of glucose in animals.
Chapter Concept :
Polysaccharides: Starch, Cellulose and Glycogen
Correct Answer: True
Solution:
Fructose, a ketohexose, forms five-membered cyclic furanose structures by the addition of the hydroxyl group at C-5 to the ketonic group at C-2, resulting in the formation of α- and β-D-fructofuranose.
Chapter Concept :
Fructose Structure and Cyclic Forms
Correct Answer: False
Solution:
Denaturation affects the secondary and tertiary structures of proteins, but the primary structure remains intact.
Chapter Concept :
Protein Structure and Denaturation
Correct Answer: True
Solution:
Denaturation affects the secondary and tertiary structures of proteins, causing them to lose their functional shape, but the primary structure, which is the sequence of amino acids, remains unchanged.
Chapter Concept :
Protein Structure and Denaturation
Correct Answer: True
Solution:
DNA contains -D-2-deoxyribose as its sugar component, whereas RNA contains -D-ribose.
Chapter Concept :
Nucleic Acid Structure and Function
Correct Answer: True
Solution:
Naturally occurring α-amino acids have an asymmetric α-carbon atom, making them optically active, and they predominantly exist in the L-configuration.
Chapter Concept :
Amino Acid Properties and Classification
Correct Answer: True
Solution:
Steroid hormones are indeed produced by the adrenal cortex and gonads. Glucocorticoids and mineralocorticoids are produced by the adrenal cortex, while testosterone, estradiol, and progesterone are produced by the gonads.
Chapter Concept :
Steroid Hormones and Adrenal/Gonadal Functions
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