The Makeup and Properties of Macromolecules
In AP Biology, understanding the makeup and properties of macromolecules is essential as they form the basis of life. Macromolecules like carbohydrates, lipids, proteins, and nucleic acids interact with water and water vapor, influencing their chemical properties and biological functions. These properties, such as solubility, reactivity, and structural integrity, are crucial for processes like energy storage, cellular structure, and genetic information transmission, highlighting their significance in biological systems.
Learning Objectives
By studying the makeup and properties of macromolecules in AP Biology, students will learn about the structure and functions of carbohydrates, lipids, proteins, and nucleic acids. They will understand how these macromolecules interact with water, their roles in biological processes, and their chemical properties such as solubility, reactivity, and structural integrity. Additionally, students will explore the importance of these macromolecules in energy storage, cellular structure, and genetic information transmission, providing a comprehensive understanding of their significance in living organisms.
Types of Macromolecules
Carbohydrates
Structure
- Monomers: Monosaccharides (simple sugars like glucose, fructose)
- Polymers: Disaccharides (sucrose, lactose) and polysaccharides (starch, glycogen, cellulose)
Properties
- Energy Storage: Starch (plants), glycogen (animals)
- Structural Components: Cellulose (plant cell walls), chitin (exoskeletons of arthropods)
- Solubility: Generally soluble in water due to hydroxyl groups, forming hydrogen bonds with water molecules
Functions
- Energy Source: Quick energy via glucose
- Structural Support: Cellulose in plants, chitin in arthropods
- Cell Recognition: Glycoproteins and glycolipids on cell surfaces
Lipids
Structure
- Components: Glycerol and fatty acids (triglycerides), phosphate groups (phospholipids), four-ring structures (steroids)
- Types: Triglycerides, phospholipids, steroids, and waxes
Properties
- Hydrophobic: Insoluble in water due to nonpolar hydrocarbon chains
- Saturated vs. Unsaturated: Saturated fats have no double bonds (solid at room temperature), unsaturated fats have one or more double bonds (liquid at room temperature)
Functions
- Energy Storage: Long-term energy storage in adipose tissue
- Membrane Structure: Phospholipids form bilayers in cell membranes
- Hormones: Steroids like testosterone and estrogen
- Insulation and Protection: Fat provides insulation and cushioning
Proteins
Structure
- Monomers: Amino acids (20 different kinds)
- Polymers: Polypeptides (proteins are made up of one or more polypeptides)
Levels of Protein Structure
- Primary Structure: Sequence of amino acids
- Secondary Structure: Alpha helices and beta sheets formed by hydrogen bonding
- Tertiary Structure: 3D folding due to interactions between R groups (side chains)
- Quaternary Structure: Association of multiple polypeptide chains
Properties
- Diverse Functions: Enzymes, structural proteins, transport proteins, antibodies
- Solubility: Depends on the amino acid composition; some proteins are soluble in water, others are not
Functions
- Catalysis: Enzymes accelerate biochemical reactions
- Structure: Collagen in connective tissues, keratin in hair and nails
- Transport: Hemoglobin carries oxygen in blood
- Defense: Antibodies in the immune system
- Regulation: Hormones like insulin
Nucleic Acids
Structure
- Monomers: Nucleotides (composed of a sugar, phosphate group, and nitrogenous base)
- Polymers: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)
Properties
- Double Helix: DNA is double-stranded and forms a double helix
- Single-Stranded: RNA is usually single-stranded
- Base Pairing: DNA (A-T, G-C), RNA (A-U, G-C)
Functions
- Genetic Information: DNA stores genetic information
- Protein Synthesis: RNA is involved in translating genetic information into proteins (mRNA, tRNA, rRNA)
- Regulation: Some RNA molecules regulate gene expression
Polymerization and Breakdown of Macromolecules
Dehydration Synthesis (Condensation Reaction)
- Process: Monomers are joined to form polymers by removing a water molecule
- Example: Formation of a peptide bond between amino acids
Hydrolysis
- Process: Polymers are broken down into monomers by adding a water molecule
- Example: Digestion of starch into glucose molecules
Enzymes and Macromolecules
Role of Enzymes
- Catalysts: Speed up chemical reactions without being consumed
- Specificity: Each enzyme is specific to a particular substrate
- Active Site: The region on the enzyme where the substrate binds
Enzyme Function
- Activation Energy: Enzymes lower the activation energy required for a reaction
- Factors Affecting Activity: Temperature, pH, substrate concentration, and presence of inhibitors or activators
Examples of Macromolecules in Biological Systems
Carbohydrates
- Glycogen: Energy storage in liver and muscle cells
- Cellulose: Provides structural support in plant cell walls
- Sucrose: Transported in plant sap
Lipids
- Triglycerides: Stored in adipose tissue as energy reserves
- Phospholipids: Form the lipid bilayer of cell membranes
- Cholesterol: A component of cell membranes and precursor of steroid hormones
Proteins
- Hemoglobin: Transports oxygen in red blood cells
- Antibodies: Immune proteins that recognize and neutralize pathogens
- Enzymes: Catalysts like amylase, lipase, and protease
Nucleic Acids
- DNA: Stores genetic information in the nucleus
- mRNA: Carries genetic information from DNA to the ribosome for protein synthesis
- tRNA: Transfers amino acids to the ribosome during protein synthesis