Fundamental Concepts in General Biology: Atoms, Molecules, and Biological Macromolecules

Course Structure and Expectations

Overview of BILD 1

This section introduces the foundational expectations and structure of a General Biology course, emphasizing the importance of understanding biological organization from atoms to cells.

• Course Structure: Students are expected to grasp key biological concepts, terminology, and the relationships between structure and function at various levels of biological organization.

• Expectations: Develop reasoning skills to compare and contrast biological entities based on their composition and size.

Biological Organization and Relative Size

Atoms, Molecules, Viruses, Organelles, and Cells

Understanding the composition and relative size of biological structures is essential for reasoning about their function and interactions.

• Atoms: The smallest units of matter, consisting of protons, neutrons, and electrons.

• Molecules: Groups of atoms bonded together (e.g., H2O, CO2).

• Viruses: Non-cellular entities composed of nucleic acids and proteins, smaller than cells but larger than most molecules.

• Organelles: Specialized structures within eukaryotic cells (e.g., mitochondria, nucleus).

• Prokaryotic vs. Eukaryotic Cells: Prokaryotic cells lack membrane-bound organelles; eukaryotic cells contain them and are generally larger.

Example: A water molecule is much smaller than a virus, which is in turn smaller than a mitochondrion.

Chemical Foundations of Life

Types of Matter: Atoms, Elements, Molecules, Compounds

Biological systems are composed of different types of matter, each with distinct properties.

• Atom: The basic unit of a chemical element (e.g., carbon, hydrogen).

• Element: A substance consisting of one type of atom (e.g., O2).

• Molecule: Two or more atoms bonded together (e.g., O2, H2O).

• Compound: A molecule containing two or more different elements (e.g., CO2).

Chemical Bonds

Chemical bonds hold atoms together in molecules and influence the properties of biological molecules.

• Covalent Bond: Atoms share electrons; strong bond (e.g., H2O).

• Ionic Bond: Electrons are transferred from one atom to another, creating charged ions (e.g., NaCl); moderate strength.

• Hydrogen Bond: Weak attraction between a hydrogen atom in a polar molecule and an electronegative atom (e.g., between water molecules).

Energy to Break Bonds: Covalent > Ionic > Hydrogen. Types of Atoms Involved: Covalent (nonmetals), Ionic (metals and nonmetals), Hydrogen (H with O, N, or F).

Electronegativity and Polarity

The relative electronegativity of atoms in a covalent bond determines bond polarity.

• Electronegativity: The tendency of an atom to attract electrons in a bond.

• Polar Covalent Bond: Unequal sharing of electrons (e.g., H2O).

• Nonpolar Covalent Bond: Equal sharing of electrons (e.g., O2).

Example: In water, oxygen is more electronegative than hydrogen, creating a polar molecule.

Hydrogen Bonding and Water Solubility

Hydrogen bonds arise from polar covalent bonds and influence molecular interactions and solubility.

• Hydrogen Bonding: Occurs when a hydrogen atom covalently bonded to an electronegative atom is attracted to another electronegative atom.

• Polarity and Solubility: Polar molecules dissolve in water (hydrophilic); nonpolar molecules do not (hydrophobic).

Example: Salt (NaCl) dissolves in water due to ionic and polar interactions; oil does not dissolve due to nonpolarity.

Organic Chemistry in Biology

Organic Compounds and Carbon

Organic compounds are molecules containing carbon and are central to biological diversity.

• Organic Compounds: Molecules with carbon-hydrogen bonds (e.g., carbohydrates, proteins, lipids, nucleic acids).

• Carbon's Versatility: Carbon can form four covalent bonds, allowing for diverse structures (chains, rings, branches).

Example: Glucose (C6H12O6) and fatty acids have different structures due to carbon's bonding properties.

Carbohydrates and Lipids

Carbohydrates and lipids are essential macromolecules with distinct structures and functions.

• Carbohydrates: Composed of monosaccharides; provide energy and structural support (e.g., starch, cellulose).

• Lipids: Hydrophobic molecules including fats, oils, and phospholipids; function in energy storage and membrane structure.

Structure-Function Relationship: The arrangement of atoms in carbohydrates and lipids determines their biological roles.

Phospholipids and Membrane Formation

Phospholipids spontaneously form bilayers in water due to their amphipathic nature.

• Phospholipid Structure: Glycerol backbone, two fatty acid tails (hydrophobic), and a phosphate group (hydrophilic).

• Lipid Bilayer Formation: Hydrophilic heads face water; hydrophobic tails face inward, forming cell membranes.

Hydrophobic vs. Hydrophilic Molecules

The chemical structure of a molecule determines its affinity for water.

• Hydrophobic: Nonpolar molecules that do not dissolve in water (e.g., oils).

• Hydrophilic: Polar or charged molecules that dissolve in water (e.g., sugars, salts).

Biological Macromolecules

Types of Macromolecules

There are four major classes of biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids (DNA and RNA)

DNA and RNA: Structure and Function

DNA and RNA are nucleic acids that store and transmit genetic information.

• DNA: Double helix structure; stores genetic information.

• RNA: Single-stranded; involved in protein synthesis and gene regulation.

• Structure-Function Relationship: The sequence of nucleotides encodes information; complementary base pairing enables replication.

Chargaff’s Rules: In double-stranded DNA, %A = %T and %G = %C. Example: If a DNA sample has 30% A, it must have 30% T, 20% G, and 20% C.

Proteins: Structure and Function

Proteins are polymers of amino acids with diverse functions determined by their structure.

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Local folding (α-helix, β-sheet).

• Tertiary Structure: Overall 3D shape.

• Quaternary Structure: Association of multiple polypeptides.

Structure-Function Relationship: The shape of a protein determines its function (e.g., enzymes, antibodies).

Amino Acids: Structure and Properties

Amino acids are the building blocks of proteins, each with a central carbon, amino group, carboxyl group, hydrogen, and variable side chain (R group).

• Parts of an Amino Acid: Amino group (–NH2), carboxyl group (–COOH), hydrogen, and R group.

• Side Chain (R group): Determines the chemical properties and interactions of the amino acid.

Example: Hydrophobic side chains cluster inside proteins; hydrophilic side chains interact with water.

Predicting Protein Structure and Function

The properties of amino acid side chains influence protein folding and function at all structural levels.

• Primary Structure: Determined by amino acid sequence.

• Secondary, Tertiary, Quaternary Structures: Influenced by side chain interactions (hydrogen bonds, ionic bonds, hydrophobic interactions, disulfide bridges).

Example: A mutation changing a hydrophobic amino acid to a hydrophilic one can disrupt protein folding and function.

Additional info: These notes expand on the provided outline with academic context, definitions, and examples to ensure a comprehensive understanding suitable for exam preparation.