Biomolecules — Class 12 Chemistry NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 12 Chemistry chapter "Biomolecules" — 5 important questions with detailed answers for CBSE board exam preparation.
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TL;DR: Free step-by-step NCERT solutions for Class 12 Chemistry chapter "Biomolecules" — 5 important questions with detailed answers for CBSE board exam prep…
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Key Questions Covered:
- What are carbohydrates? Classify them and give examples of monosaccharides, d…
- Explain the structure of glucose. Draw the Fischer projection and the Haworth…
- Explain amino acids. What is a peptide bond? Write the general structure of a…
- What are nucleic acids? Describe the structure of DNA, including the role of …
- Explain the structure and properties of proteins. What are enzymes, and how d…
Solutions Summary:
| Question | Status |
|---|---|
| What are carbohydrates? Classify them and give examples o… | ✓ Solved |
| Explain the structure of glucose. Draw the Fischer projec… | ✓ Solved |
| Explain amino acids. What is a peptide bond? Write the ge… | ✓ Solved |
| What are nucleic acids? Describe the structure of DNA, in… | ✓ Solved |
| Explain the structure and properties of proteins. What ar… | ✓ Solved |
Showing 5 of 5 questions
Q1: What are carbohydrates? Classify them and give examples of monosaccharides, disaccharides, and polysaccharides.
Carbohydrates: Organic compounds composed of carbon, hydrogen, and oxygen with the general formula Cn(H2O)m. They are polyhydroxy aldehydes or ketones and their derivatives.
General characteristics:
- Soluble in water (multiple OH groups)
- Taste sweet (especially sugars)
- Provide energy (4 kcal/gram)
- Contain C=O and multiple C-OH groups
Classification:
1. MONOSACCHARIDES (simple sugars)
Definition: Carbohydrates that cannot be hydrolyzed into smaller sugars
General formula: CnH2nOn (where...
Q2: Explain the structure of glucose. Draw the Fischer projection and the Haworth structure. Discuss mutarotation.
Glucose (also called dextrose or grape sugar):
Molecular formula: C6H12O6
Type: Aldohexose (6-carbon aldose sugar)
Structural representations:
1. FISCHER PROJECTION (open-chain form):
Shows the 2D representation of the 3D structure
CHO
|
CHOH
|
CHOH
|
CHOH
|
CHOH
|
CH2OH
Or more detailed Fischer structure:
CHO (C1 - aldehyde carbon)
|
H-C-OH (C2 - chiral center)
|
HO-C-H (C...
Q3: Explain amino acids. What is a peptide bond? Write the general structure of an amino acid and describe how proteins are formed from amino acids.
Amino acids: Organic compounds that contain both an amino group (-NH2) and a carboxyl group (-COOH) bonded to the same carbon atom (α-carbon).
General structure of amino acid:
Carboxyl group
|
v
COOH
|
H2N-C-H (α-carbon)
|
R (side chain)
^
|
Amino group
Structure details:
- Central carbon (α-carbon): sp3 hybridized
- Four groups bonded to α-carbon:
1. Carboxyl group (-COOH)
2. Amino gro...
Q4: What are nucleic acids? Describe the structure of DNA, including the role of nucleotides and the double helix structure.
Nucleic acids: Polymers of nucleotides that store and transmit genetic information. Two main types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
NUCLEOTIDES (building blocks):
A nucleotide consists of three components:
1. A five-carbon sugar (pentose)
- DNA: Deoxyribose (C5H10O4) - lacks one oxygen at C2
- RNA: Ribose (C5H10O5) - has OH at C2
2. A nitrogenous base (purine or pyrimidine)
- DNA bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T)
- RNA bases: Adenin...
Q5: Explain the structure and properties of proteins. What are enzymes, and how do they catalyze biochemical reactions?
PROTEINS:
Definition: Large polypeptides composed of amino acids linked by peptide bonds, with specific 3D structures that determine their functions.
Composition:
- Primarily C, H, O, N
- Some contain S (from cysteine)
- Some contain metal ions (Fe, Zn, Mg, Cu)
- Molecular weight: 5,000 to >100,000 Da
Structural properties of proteins:
1. PRIMARY STRUCTURE:
Linear sequence of amino acids in the polypeptide chain
- Determined by the genetic code (DNA)
- Unique sequence for each protein
- E...
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