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Study Notes on Biological Macromolecules

Carbohydrates

Overview

Carbohydrates are biological macromolecules composed of carbon (C), hydrogen (H), and oxygen (O) with a general formula of CnH{2n}O_n, typically with a 1:2:1 ratio of these elements. They serve vital roles in energy transportation, storage, and structural components in organisms.

Types of Carbohydrates

  1. Monosaccharides - Single sugar units (e.g., glucose, fructose).

  2. Disaccharides - Two monosaccharides linked via dehydration synthesis (e.g., sucrose, lactose).

  3. Polysaccharides - Long-chain carbohydrates (e.g., starch, glycogen, cellulose).

Functions

  • Energy source: Carbohydrates hold energy in C-H covalent bonds.

  • Structural role: Found in cellulose (plants) and chitin (arthropods).

Lipids

Definition

Lipids are heterogeneous groups of hydrophobic organic molecules that are insoluble in water, composed mainly of hydrocarbons.

Characteristics

  • Amphipathic lipid: molecules that have both hydrophilic (water-loving) and hydrophobic (water-fearing) properties.

  • Hydrophobic: nonpolar, do not mix with water.

Types of Lipids

  1. Triglycerides - Comprised of glycerol and three fatty acid chains. Used for energy storage.

  2. Phospholipids - Form biological membranes; contain hydrophilic heads and hydrophobic tails.

  3. Steroids - Composed of four fused hydrocarbon rings, such as cholesterol.

Biological Importance

  • Store and provide energy.

  • Structure and functionality in cell membranes (phospholipids).

  • Hormonal functions (steroids).

Proteins

Overview

Proteins are macromolecules composed of amino acids linked by peptide bonds and play essential roles in biological processes.

Structure

Proteins have four levels of structure:

  1. Primary structure - Sequence of amino acids.

  2. Secondary structure - Local folding into helices or sheets (e.g., alpha-helix, beta-sheet).

  3. Tertiary structure - Overall three-dimensional shape.

  4. Quaternary structure - Assembly of multiple polypeptide chains.

Functions

  • Catalysts (enzymes).

  • Structural components (muscles, hair).

  • Transport (hemoglobin).

Nucleic Acids

Definition

Nucleic Acids are macromolecules that store and transmit genetic information. There are two types:

  • DNA (deoxyribonucleic acid): Double-helix structure that stores genetic code.

  • RNA (ribonucleic acid): Single-stranded molecule that translates DNA into proteins.

Components

  • Nucleotides: The building blocks of nucleic acids, composed of a sugar, phosphate group, and nitrogenous base.

    • Nitrogenous bases in DNA: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

    • Nitrogenous bases in RNA: Adenine (A), Uracil (U), Cytosine (C), Guanine (G).

Functions

  • DNA serves as the template for genetic information.

  • RNA facilitates the synthesis of proteins from DNA instruction.

Summary of Biological Macromolecules

The interplay among carbohydrates, lipids, proteins, and nucleic acids enables the vast diversity of biological structures and functions. Each macromolecule plays a unique and vital role, contributing to the complexity of life forms.