lecture 10/23/25 bio112

Carbohydrates and Lipids

Overview

  • Discussion of carbohydrates (sugars) and lipids (fats) focusing on their structures, functions, and interactions with water.

Carbohydrates

1. Atoms Present

  • Carbohydrates consist of three types of atoms:

    • Carbon (C)

    • Hydrogen (H)

    • Oxygen (O)

  • General formula for carbohydrates: C, H, O.

2. Types of Carbohydrates

  • Monosaccharides:

    • Definition: Single unit or single piece of sugar.

    • Example: Glucose.

  • Polysaccharides:

    • Definition: Many pieces or units of sugar.

    • Example: Starch (composed of multiple glucose units).

3. Terminology

  • Mono: Means "one"; relates to single units (monomers).

  • Poly: Means "many"; relates to multiple units (polymers).

  • Monosaccharide: Single unit of sugar (e.g., glucose).

  • Polysaccharide: Several monosaccharides linked together (e.g., starch).

  • Glycosidic linkage: The bond formed between monosaccharides.

4. Functions

  • Carbohydrates are primary energy sources for the body.

  • Hydrophilic: Carbohydrates love water. They can mix with water due to their polar nature.

  • Quick Energy: Sugars provide rapid energy. They are quickly metabolized to provide fuel for cellular functions.

5. Interaction with Water

  • All carbohydrates are polar molecules and interact positively with water due to the presence of hydroxyl (-OH) groups.

6. Examples

  • Monosaccharide Example: Glucose, found in honey.

  • Polysaccharide Example: Starch, used in foods like bread.

Lipids

1. Atoms Present

  • Lipids, like carbohydrates, also consist of C, H, and O atoms but are arranged differently.

2. Types of Lipids

  • Triglycerides: Composed of three fatty acids and one glycerol molecule.

    • Fatty acids: Monomers of lipids, which can be saturated or unsaturated.

  • Phospholipids: Composed of glycerol, two fatty acids, and a phosphate group; vital for cell membranes.

3. Terminology

  • Hydrophobic: Lipids do not mix with water due to their nonpolar nature.

  • Saturated Fat: All carbon-hydrogen bonds are single; solid at room temperature (e.g., butter).

  • Unsaturated Fat: Contains one or more double bonds; liquid at room temperature (e.g., oils).

    • Monounsaturated: One double bond.

    • Polyunsaturated: Multiple double bonds.

  • Ester bond: The bond formed between fatty acids and glycerol.

4. Functions

  • Lipids serve as long-term energy storage, insulation, and protection (e.g., stored fat).

  • They are also important components of cell membranes (phospholipids).

5. Interaction with Water

  • Lipids are hydrophobic molecules that do not mix well with water due to the lack of polar functional groups compared to carbohydrates.

6. Examples

  • Triglyceride Examples: Butter (saturated fat), olive oil (unsaturated fat).

Chemical Reactions

1. Dehydration Synthesis

  • A chemical reaction where two molecules combine, and water is released as a byproduct.

  • Example: Forming glycosidic linkages in carbohydrates.

2. Hydrolysis

  • A chemical reaction that breaks down molecules by the addition of water.

  • Example: Splitting polysaccharides into monosaccharides.

3. Importance of Water in Reactions

  • Water is crucial in both dehydration synthesis (removed to form linkages) and hydrolysis (added to break linkages).

Summary of Differences between Carbohydrates and Lipids

  • Carbohydrates:

    • Composed mainly of CHO.

    • Hydrophilic (water-loving).

    • Function primarily for quick energy.

  • Lipids:

    • Composed of CHO but arranged differently.

    • Hydrophobic (water-fearing).

    • Serve as long-term energy storage, insulation, and make up cell membranes.

Isomerism

  • Isomers: Molecules with the same atoms but different structural arrangements (e.g., glucose and fructose).

  • The different arrangements lead to different properties, despite identical molecular formulas.

Functional Groups and Properties

  • Functional groups in carbohydrates (primarily hydroxyl groups) determine their polarity and solubility in water.

  • The presence of oxygen in functional groups leads to their hydrophilic properties.

  • The differences in functionality based on the presence or absence of certain atoms (especially O) distinguishes lipids from carbohydrates.