MHT-CET Chemistry · Free notes
Biomolecules — MHT-CET Chemistry
Biomolecules is about two questions a paper in MHT-CET Chemistry and almost never HARD — two of its 149 past-year questions. 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.
The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.
Subtopic notes
Carbohydrates: Classification, Structure and Reactions
35 PYQsCarbohydrates are polyhydroxy aldehydes or ketones (or what hydrolyses to them), classed by the number of sugar units; glucose is an aldohexose with four chiral carbons that closes into a six-membered pyranose ring between C-1 and C-5, fructose a ketohexose that closes into a five-membered furanose ring, and the reactions of the open-chain form prove each part of the structure.
Glycosidic Linkages in Di- and Polysaccharides
28 PYQsA glycosidic linkage is the C–O–C bridge formed when the anomeric OH of one sugar condenses with an OH of another: alpha-1,4 in maltose, amylose and the chains of amylopectin and glycogen, alpha-1,6 at their branch points, beta-1,4 in lactose and cellulose, and alpha-1,beta-2 between C-1 of glucose and C-2 of fructose in sucrose.
Amino Acids, Peptides and Proteins
46 PYQsAlpha-amino acids carry an amino group and a carboxyl group on the same carbon and differ in the side chain R, which sets the class (acidic, basic, neutral) and the three- and one-letter code; they join through peptide (amide) bonds — n residues, n minus 1 bonds — into fibrous or globular proteins whose alpha-helix has 3.6 residues per turn.
Nucleic Acids: Nucleotides, Bases and the Double Helix
25 PYQsA nucleotide is a pentose sugar (ribose in RNA, 2-deoxyribose in DNA) carrying a nitrogen base at C-1 prime and a phosphate at C-5 prime; the bases are purines (adenine, guanine — nitrogens at 1, 3, 7, 9, joined through N-9) and pyrimidines (cytosine, thymine, uracil — nitrogens at 1 and 3, joined through N-1), and nucleotides link by 3 prime to 5 prime phosphodiester bonds into strands that pair A with T and G with C in the right-handed Watson–Crick double helix.
Lipids, Enzymes and Other Biomolecules
15 PYQsFats and oils are triglycerides — triesters of glycerol with three fatty acids, hydrolysed by three water molecules and saponified to soap, the sodium or potassium salt of a higher fatty acid; the common fatty acids are counted by carbons and double bonds (linolenic 18:3), enzymes are globular protein catalysts named for their substrate and site, and haemoglobin is the biological coordination compound.
Formula & revision sheet
7 formulas · 2 reference tables · 9 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
7 formulas · 2 reference tables · 9 gotchas across all subtopics — the exam-eve cheat-sheet
Formulas (2)
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
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 |
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
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. |
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
Formulas (2)
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
Watch out for (1)
- Linoleic for linolenic→ Triglycerides, Fatty Acids, Soap and Enzymes
PYQ weightage by concept
9 concepts · 149 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
9 concepts · 149 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Classification, and the Structures of Glucose and Fructose | 14 | 9% |
| Reactions of Glucose: What Each One Proves | 7 | 5% |
| Concept | PYQs | Share |
|---|---|---|
| Sucrose, Maltose, Lactose, Raffinose, Stachyose: the Linkage and the Hydrolysis Count | 13 | 9% |
| Starch, Glycogen and Cellulose | 6 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| The Amino Acids by Side Chain: Class, Code and the Essential Ones | 17 | 11% |
| Peptide Bonds, Protein Shape and Structure Levels | 10 | 7% |
| Concept | PYQs | Share |
|---|---|---|
| Nucleotide Anatomy: Sugar, Base and Phosphate by Position | 14 | 9% |
| The Phosphodiester Backbone and the Watson–Crick Double Helix | 2 | 1% |
| Concept | PYQs | Share |
|---|---|---|
| Triglycerides, Fatty Acids, Soap and Enzymes | 4 | 3% |
Test yourself on Biomolecules
20 past MHT-CET questions from this chapter, timed at 18 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.