MHT-CET Chemistry · Teaching notes

Biomolecules — MHT-CET Chemistry

Biomolecules is about two questions a paper in MHT-CET Chemistry and almost never HARD — two of its past-year questions in eighty-eight. It is a chapter of named facts with a small amount of counting: which sugar is which and what its ring is, the reactions that prove glucose's structure, the glycosidic linkage in every disaccharide and polysaccharide, the twenty amino acids by class and code, protein shape, and the numbering of the purine and pyrimidine bases, the sugar and the phosphate in a nucleotide. Five pages in the book's order. Every PYQ is tagged.

Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.

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Subtopic notes

PYQ weightage by concept

9 concepts · 88 PYQs — where the marks actually sit, so you know what to drill first

Carbohydrates: Classification, Structure and Reactions21 PYQs · 24%

Concept	PYQs	Share
Classification, and the Structures of Glucose and Fructose	14	16%
Reactions of Glucose: What Each One Proves	7	8%

Glycosidic Linkages in Di- and Polysaccharides19 PYQs · 22%

Concept	PYQs	Share
Sucrose, Maltose, Lactose, Raffinose, Stachyose: the Linkage and the Hydrolysis Count	13	15%
Starch, Glycogen and Cellulose	6	7%

Amino Acids, Peptides and Proteins27 PYQs · 31%

Concept	PYQs	Share
The Amino Acids by Side Chain: Class, Code and the Essential Ones	17	19%
Peptide Bonds, Protein Shape and Structure Levels	10	11%

Nucleic Acids: Nucleotides, Bases and the Double Helix16 PYQs · 18%

Concept	PYQs	Share
Nucleotide Anatomy: Sugar, Base and Phosphate by Position	14	16%
The Phosphodiester Backbone and the Watson–Crick Double Helix	2	2%

Lipids, Enzymes and Other Biomolecules5 PYQs · 6%

Concept	PYQs	Share
Triglycerides, Fatty Acids, Soap and Enzymes	5	6%

Formula & revision sheet

7 formulas · 2 reference tables · 9 gotchas across all subtopics — the exam-eve cheat-sheet

Carbohydrates: Classification, Structure and Reactions

Formulas (2)

Classification, and the Structures of Glucose and Fructose · Glucose and fructose rings $\text{Glucose: C-1 (CHO)} + \text{C-5 OH} \to \text{pyranose (hemiacetal)};\quad \text{Fructose: C-2 (C=O)} + \text{C-5 OH} \to \text{furanose (hemiketal)}$
Reactions of Glucose: What Each One Proves · Mild and strong oxidation $\text{Glucose} \xrightarrow{\text{Br}_2/\text{H}_2\text{O}} \text{gluconic acid (1 COOH)};\quad \text{Glucose} \xrightarrow{\text{conc. HNO}_3} \text{saccharic acid (2 COOH)}$

Watch out for (2)

Hemiacetal for fructose, three chiral carbons for glucose
→ Classification, and the Structures of Glucose and Fructose
Counting the carbonyl carbon as an OH
→ Reactions of Glucose: What Each One Proves

Glycosidic Linkages in Di- and Polysaccharides

Formulas (1)

Starch, Glycogen and Cellulose · Three glucose polymers $\text{amylose: } \alpha\text{-1,4};\quad \text{amylopectin / glycogen: } \alpha\text{-1,4} + \alpha\text{-1,6};\quad \text{cellulose: } \beta\text{-1,4}$

Reference tables (1)

Sucrose, Maltose, Lactose, Raffinose, Stachyose: the Linkage and the Hydrolysis Count5 rows

Sugar	Units	Linkage	Reducing?	Glucose per mole
Maltose	Glucose + glucose	alpha-1,4	Yes	2
Lactose	Galactose + glucose	beta-1,4	Yes	1
Sucrose	Glucose + fructose	C-1 (alpha-Glc) to C-2 (beta-Fru)	No	1 Both anomeric carbons are in the bond — hence non-reducing and invert sugar on hydrolysis.
Raffinose	Gal + Glc + Fru	Trisaccharide	No	1
Stachyose	2 Gal + Glc + Fru	Tetrasaccharide	No	1

Maltose is the only common disaccharide that gives two glucose per mole.

Watch out for (2)

Lactose as the double-glucose sugar
→ Sucrose, Maltose, Lactose, Raffinose, Stachyose: the Linkage and the Hydrolysis Count
Amylose with a 1,6 branch
→ Starch, Glycogen and Cellulose

Amino Acids, Peptides and Proteins

Formulas (1)

Peptide Bonds, Protein Shape and Structure Levels · Peptide-bond count $n\ \text{amino acids} \to (n-1)\ \text{peptide bonds};\qquad \alpha\text{-helix: } 3.6\ \text{residues per turn}$

Reference tables (1)

The Amino Acids by Side Chain: Class, Code and the Essential Ones12 rows

Amino acid	3-letter / 1-letter	Side chain R	Class
Glycine	Gly / G	–H	Neutral, achiral
Alanine	Ala / A	–CH₃	Neutral
Serine	Ser / S	–CH₂OH	Neutral
Threonine	Thr / T	–CH(OH)CH₃	Neutral, essential
Methionine	Met / M	–CH₂CH₂SCH₃	Neutral, essential, has S
Leucine / Valine	Leu / L · Val / V	isobutyl · isopropyl	Neutral, essential
Tryptophan	Trp / W	indolylmethyl	Neutral, essential, heterocyclic
Aspartic acid	Asp / D	–CH₂COOH	Acidic D is aspartic acid; E is glutamic acid.
Glutamic acid	Glu / E	–CH₂CH₂COOH	Acidic
Lysine	Lys / K	–(CH₂)₄NH₂	Basic, essential
Arginine	Arg / R	guanidino	Basic
Histidine	His / H	imidazolylmethyl	Basic, essential, heterocyclic The one that is basic, essential and heterocyclic at once — the favourite answer.

Class follows the side chain: a second COOH is acidic, a second basic N is basic, everything else neutral.

Watch out for (2)

Gln and Asn read as acidic
→ The Amino Acids by Side Chain: Class, Code and the Essential Ones
Insulin as fibrous
→ Peptide Bonds, Protein Shape and Structure Levels

Nucleic Acids: Nucleotides, Bases and the Double Helix

Formulas (2)

Nucleotide Anatomy: Sugar, Base and Phosphate by Position · Ring nitrogens and the glycosidic N $\text{purine: N-1, 3, 7, 9 (sugar at N-9)};\quad \text{pyrimidine: N-1, 3 (sugar at N-1)};\quad \text{phosphate at C-5}'$
The Phosphodiester Backbone and the Watson–Crick Double Helix · Base pairing $\text{A}=\text{T}\ (2\ \text{H-bonds}),\quad \text{G}\equiv\text{C}\ (3\ \text{H-bonds});\quad 5'\text{-phosphate} \cdots 3'\text{-OH}$

Watch out for (2)

Purine N at 1, 3, 5
→ Nucleotide Anatomy: Sugar, Base and Phosphate by Position
–C–O–C– as the backbone
→ The Phosphodiester Backbone and the Watson–Crick Double Helix

Lipids, Enzymes and Other Biomolecules

Formulas (1)

Triglycerides, Fatty Acids, Soap and Enzymes · Triglyceride hydrolysis $\text{triglyceride} + 3\,\text{H}_2\text{O} \to \text{glycerol} + 3\,\text{RCOOH};\qquad \text{linolenic acid: } \text{C}_{18},\ 3\ \text{C=C}$

Watch out for (1)

Linoleic for linolenic
→ Triglycerides, Fatty Acids, Soap and Enzymes