B1.1 Carbohydrates and lipids

Q: What happens in a hydrolysis reaction?

A large molecule is broken into smaller molecules using water, which is split into -H and -OH groups to form new bonds. Examples:

• Polypeptide → Amino acids

• Polysaccharide → Monosaccharides

• Glyceride → Fatty acids + Glycerol

Q: What are monosaccharides, and what is their general formula?

A: Monosaccharides are simple sugars (monomers) with the ratio C:H:O = 1:2:1. Examples:

• Pentoses: C5H10O5C5​H10​O5​

• Hexoses: C6H12O6C6​H12​O6​

Q: How do alpha and beta glucose differ?

A: They differ in the orientation of the -OH group on carbon 1 (alpha: downward, beta: upward).

Q: What is their role in cell-cell recognition?

A: Oligosaccharides on glycoproteins/glycolipids bind to proteins on adjacent cells, enabling recognition (e.g., ABO blood groups).

Q: Why are lipids hydrophobic?

A: They lack charged/polar groups and dissolve in non-polar solvents (e.g., fats in toluene).

Q: Compare lipids and glucose:

Q: Compare saturated vs. unsaturated fatty acids:

• Saturated: No double bonds (e.g., stearic acid, solid at room temp).

• Unsaturated: 1+ double bonds (e.g., oleic acid, liquid at room temp).

Q: What causes lower melting points in unsaturated fats?

A: Double bonds create kinks, preventing tight packing.

Q: How are triglycerides formed?

A: Condensation of glycerol + 3 fatty acids (ester bonds form).

Q: Why are phospholipids amphipathic?

A: Hydrophilic phosphate head + hydrophobic fatty acid tails.

Q: What is their role in membranes?

A: Form bilayers: heads face water, tails cluster inward.

Q: What is the structure of steroids?

A: Four fused carbon rings (e.g., cholesterol, testosterone).

Q: Why can steroids cross membranes?

A: Hydrophobic nature allows diffusion through bilayers.

Q: Why are triglycerides efficient energy stores?

A: Release 2x energy per gram vs. carbs; inert, compact, and insulate heat.