Biomolecules
Easy Overview
Carbs give you energy, proteins build your muscles, enzymes digest your food. Biomolecules is the chemistry of living things. It's less about reactions and more about structures — how these huge molecules are put together and what they do in your body.
Carbohydrates
Sugars and starches. Monosaccharides (glucose, fructose) are single sugar units. Disaccharides (sucrose, lactose) are two linked. Polysaccharides (starch, cellulose) are long chains. Glucose exists in two forms — open chain and ring. The ring form is what you mostly find in water. Glucose + Benedict's → red precipitate (classic test).
Structure of glucose
Glucose is C6H12O6. It has an aldehyde group and five -OH groups. It forms a six-membered ring (pyranose) by the aldehyde reacting with the -OH on carbon 5. The -OH at carbon 1 can be either down (α) or up (β). That α/β difference is why starch (α-linkages) is digestible but cellulose (β-linkages) is not.
Proteins and amino acids
Proteins are chains of amino acids. There are 20 standard amino acids. They link via peptide bonds (CO-NH). The sequence determines the protein's shape and function. Primary structure = sequence. Secondary = folding (α-helix, β-sheet). Tertiary = 3D shape. Quaternary = multiple chains together. Hemoglobin has 4 chains.
Enzymes
Enzymes are protein catalysts. They speed up reactions in your body by millions of times. Lock and key model: the substrate fits perfectly into the enzyme's active site. Induced fit model: the enzyme changes shape a little to grab the substrate. Enzymes are specific — one enzyme, one type of reaction.
Vitamins and hormones
Vitamins are organic compounds your body needs but can't make enough of. Fat-soluble: A, D, E, K. Water-soluble: B-complex and C. Hormones are chemical messengers. Insulin controls blood sugar. Testosterone and estrogen are steroid hormones. Deficiency of vitamins causes diseases — scurvy (C), rickets (D), night blindness (A).
Key Points
- •Monosaccharides: single sugar unit (glucose, fructose)
- •Glucose forms a pyranose ring (α and β anomers)
- •Polypeptide = chain of amino acids linked by peptide bonds
- •Proteins have 4 levels of structure: primary to quaternary
- •Enzymes are biological catalysts; lock and key model
- •Vitamins: fat-soluble (A, D, E, K) and water-soluble (B, C)
- •Deficiency of Vitamin C causes scurvy; Vitamin D causes rickets
Practice Questions
- Explain the structure of glucose. What are α and β anomers?
- Differentiate between fibrous and globular proteins with examples.
- What is denaturation of proteins? Give an example.
- Write the difference between fat-soluble and water-soluble vitamins.
- Explain the lock and key model of enzyme action.