10Class 12 Chemistry
Biomolecules short notes
Short notes on carbohydrates, proteins, vitamins and nucleic acids. Mostly facts, and many overlap with Biology.
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Carbohydrates
- Monosaccharides include glucose (aldose) and fructose (ketose). Disaccharides and polysaccharides are made from them.
- Sugars that reduce Tollens' or Fehling's reagents are reducing sugars. Sucrose isn't one.
- Sucrose is glucose + fructose. Maltose is glucose + glucose, and lactose is glucose + galactose.
- Glucose has anomers, α and β, which differ at C1.
- Starch has amylose and amylopectin. Glycogen is similar to amylopectin, and cellulose is made of β-glucose.
Proteins
- Amino acids join by peptide bonds. Essential ones must come from food.
- They exist as zwitterions, with charged amino and carboxyl groups.
- Structures: primary, secondary (α-helix and β-pleated sheet), tertiary and quaternary.
- Denaturation destroys the shape but not the primary structure, as in boiled egg white.
Vitamins and enzymes
- Fat-soluble: A, D, E and K. Water-soluble: B and C.
- Deficiencies: A causes night blindness, B1 beriberi, C scurvy, D rickets, E muscle weakness, and K slow clotting.
- Enzymes are biological catalysts, mostly proteins, and often named with -ase.
Nucleic acids
- A nucleoside is a base + sugar, and a nucleotide adds phosphate.
- DNA has deoxyribose, with A, G, C and T. RNA has ribose, with A, G, C and U.
- DNA is a double helix, with A pairing T and G pairing C.
Where students slip up
- Calling sucrose a reducing sugar. It isn't.
- Thinking denaturation breaks the primary structure. It doesn't.
- Mixing up nucleosides and nucleotides.
Try it on your weakest chapter.
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