Learning Goals and Outcomes

Overview of Biological Macromolecules

Biological macromolecules are large, complex molecules essential for life. The main classes include carbohydrates, lipids, proteins, and nucleic acids. Understanding their structure, composition, and function is fundamental to general biology.

• Polymers are long chains of repeating units (monomers) formed by covalent bonds.

• Macromolecules are synthesized and broken down by specific chemical reactions.

• Each class of macromolecule has unique examples and biological roles.

Carbon Compounds and Life

Importance of Carbon in Biological Molecules

Carbon is the backbone of organic molecules due to its ability to form four covalent bonds, allowing for diverse structures such as chains, rings, and branches.

• Carbon skeletons vary in length, branching, double bond position, and ring formation.

• These variations contribute to the diversity of organic molecules in living organisms.

• Carbon bonds play a crucial role in energy transformation during metabolism.

Functional Groups in Organic Molecules

Functional groups are specific groups of atoms within molecules that confer particular chemical properties and reactivity.

Function: Functional groups affect molecular shape, reactivity, and biological function.

Hydrocarbons

Structure and Properties

Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen. They are nonpolar and hydrophobic, making them important in energy storage and membrane structure.

• Hydrocarbon chains can undergo reactions that release significant energy.

• Examples include fatty acids and other lipid molecules.

Carbon Skeleton Variations

Carbon skeletons can be modified in several ways, leading to molecular diversity.

• Length: e.g., Methane (1C), Propane (3C)

• Branching: e.g., Isobutane (branched), Butane (unbranched)

• Double bond position: e.g., 1-Butene, 2-Butene

• Ring formation: e.g., Cyclohexane, Benzene

These variations influence the chemical and physical properties of molecules.

Macromolecule Formation and Breakdown

Polymerization and Hydrolysis

Macromolecules are formed and broken down by specific chemical reactions:

• Dehydration reaction: Monomers are joined to form polymers by removing water.

• Hydrolysis: Polymers are broken down into monomers by adding water.

These processes are essential for metabolism and cellular function.

Carbohydrates

Structure and Function

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as energy sources and structural components.

• Monosaccharides: Simple sugars (e.g., glucose, galactose, fructose)

• Disaccharides: Two monosaccharides joined by glycosidic linkage (e.g., sucrose, lactose)

• Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose)

Example: Lactose is a disaccharide made of glucose and galactose.

Formula for glucose:

Storage and Structural Polysaccharides

• Starch: Storage form in plants (amylose and amylopectin)

• Glycogen: Storage form in animals

• Cellulose: Structural component in plant cell walls

Polysaccharides differ in branching and linkage, affecting their properties and digestibility.

Lipids

Types and Functions

Lipids are hydrophobic molecules, including fats, phospholipids, and steroids. They are important for energy storage, membrane structure, and signaling.

Phospholipids: Have hydrophilic heads and hydrophobic tails, forming bilayers in membranes.

Saturated vs. Unsaturated Fats

• Saturated fats: No double bonds, straight chains, solid at room temperature.

• Unsaturated fats: One or more double bonds, kinked chains, liquid at room temperature.

Double bonds reduce the number of C-H bonds and affect physical properties.

Proteins

Structure and Levels of Organization

Proteins are polymers of amino acids, each with a central carbon, amino group, carboxyl group, and variable side chain (R group).

• Primary structure: Sequence of amino acids

• Secondary structure: Local folding (α-helix, β-pleated sheet) stabilized by hydrogen bonds

• Tertiary structure: Overall 3D shape, stabilized by hydrophobic interactions, ionic bonds, disulfide bridges, and van der Waals forces

• Quaternary structure: Association of multiple polypeptide chains

Protein function depends on its structure, which is determined by the sequence and interactions of amino acids.

Nucleic Acids

DNA and RNA Structure and Function

Nucleic acids store and transmit genetic information. They are polymers of nucleotides, each consisting of a sugar, phosphate group, and nitrogenous base.

Base pairing in DNA: Adenine (A) pairs with Thymine (T), Cytosine (C) pairs with Guanine (G) via hydrogen bonds.

Polarity: DNA strands have directionality (5' to 3').

Example: Nucleotide Structure

• Sugar: Deoxyribose or ribose

• Phosphate group: Attached to the 5' carbon of sugar

• Nitrogenous base: Attached to the 1' carbon of sugar

Additional info:

• Enzyme dysfunction (e.g., in Galactosemia) can result from mutations affecting protein structure and function.

• Model systems and simulations are used to predict molecular behavior and biological outcomes.