General Biology: Atoms, Molecules, Water, Macromolecules, and Nucleic Acids

Chapter 1: Atoms and Molecules

Atomic Structure and Properties

This section introduces the basic structure of atoms and the significance of atomic number and mass number in biology.

• Atom: The smallest unit of matter, composed of protons, neutrons, and electrons.

• Atomic Number: The number of protons in an atom, which defines the element.

• Mass Number: The sum of protons and neutrons in the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons. Some isotopes are radioactive and decay over time, emitting radiation.

• Ions: Atoms that have gained or lost electrons, resulting in a net charge.

Example: Carbon-12 and Carbon-14 are isotopes of carbon; Carbon-14 is radioactive.

Periodic Table and Chemical Bonds

The periodic table organizes elements by atomic number and properties. Chemical bonds form when atoms interact to achieve stable electron configurations.

• Periodic Table: Arranges elements in rows (periods) and columns (groups) based on atomic structure and properties.

• Covalent Bond: A chemical bond formed by the sharing of electron pairs between atoms.

• Ionic Bond: A bond formed by the transfer of electrons from one atom to another, resulting in oppositely charged ions.

• Electronegativity: The tendency of an atom to attract electrons in a bond. Increases across a period and decreases down a group.

Example: Water (H2O) has polar covalent bonds due to the difference in electronegativity between hydrogen and oxygen.

Types of Chemical Bonds and Interactions

Different types of bonds and interactions determine the structure and function of molecules in biology.

• Polar Covalent Bond: Electrons are shared unequally, resulting in partial charges (e.g., H2O).

• Nonpolar Covalent Bond: Electrons are shared equally (e.g., O2).

• Hydrogen Bond: A weak bond between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

• Van der Waals Interactions: Weak attractions between molecules due to temporary dipoles.

Example: Hydrogen bonds are responsible for the unique properties of water.

Chapter 2: Water and Its Properties

Structure and Properties of Water

Water is essential for life due to its unique chemical and physical properties.

• Polarity: Water is a polar molecule, with partial positive charges on hydrogen and a partial negative charge on oxygen.

• Hydrogen Bonding: Water molecules form hydrogen bonds with each other, leading to high cohesion, adhesion, and surface tension.

• High Specific Heat: Water can absorb or release large amounts of heat with little temperature change.

• High Heat of Vaporization: Water requires significant energy to change from liquid to gas.

• Density of Ice: Ice is less dense than liquid water due to the arrangement of hydrogen bonds.

Example: Water's high specific heat helps regulate temperature in organisms and environments.

Acids, Bases, and pH

Acids and bases are important in biological systems, and pH measures the concentration of hydrogen ions in a solution.

• Acid: A substance that increases the concentration of H+ ions in solution.

• Base: A substance that decreases the concentration of H+ ions or increases OH- ions.

• pH Scale: Measures the acidity or basicity of a solution. Defined as $pH = -\log_{10}[H^+]$.

• Buffer: A substance that minimizes changes in pH by accepting or donating H+ ions.

Example: Blood contains buffers to maintain a stable pH.

Chapter 3: Macromolecules – Proteins

Amino Acids and Protein Structure

Proteins are polymers of amino acids, which have a central carbon (alpha carbon) bonded to an amino group, carboxyl group, hydrogen, and a variable R group.

• Amino Acid: The building block of proteins, differing by their R group (side chain).

• Peptide Bond: A covalent bond formed between the amino group of one amino acid and the carboxyl group of another.

• Primary Structure: The sequence of amino acids in a polypeptide chain.

• Secondary Structure: Local folding into alpha helices and beta sheets, stabilized by hydrogen bonds.

• Tertiary Structure: The overall 3D shape of a polypeptide, determined by interactions among R groups.

• Quaternary Structure: The association of multiple polypeptide chains.

Example: Hemoglobin has quaternary structure, consisting of four polypeptide subunits.

Protein Function and Denaturation

Protein function depends on its structure, which can be altered by changes in temperature, pH, or chemical exposure.

• Denaturation: The loss of a protein's native structure, resulting in loss of function.

• Chaperones: Proteins that assist in the proper folding of other proteins.

• Enzyme: A protein that acts as a biological catalyst, speeding up chemical reactions.

• Active Site: The region of an enzyme where substrate binding and catalysis occur.

Example: High fever can denature enzymes, impairing their function.

Chapter 4: Nucleic Acids

Structure and Function of Nucleic Acids

Nucleic acids (DNA and RNA) are polymers of nucleotides, which store and transmit genetic information.

• Nucleotide: Consists of a phosphate group, a five-carbon sugar (ribose or deoxyribose), and a nitrogenous base.

• DNA (Deoxyribonucleic Acid): Contains deoxyribose sugar and the bases adenine (A), guanine (G), cytosine (C), and thymine (T).

• RNA (Ribonucleic Acid): Contains ribose sugar and the bases adenine (A), guanine (G), cytosine (C), and uracil (U).

• Phosphodiester Bond: The covalent bond linking nucleotides in a nucleic acid chain.

• Base Pairing: In DNA, A pairs with T and G pairs with C; in RNA, A pairs with U.

Example: The double helix structure of DNA is stabilized by hydrogen bonds between complementary bases.

Levels of Nucleic Acid Structure

Nucleic acids have primary, secondary, and tertiary structures that determine their function.

• Primary Structure: The sequence of nucleotides in a nucleic acid chain.

• Secondary Structure: Local folding patterns, such as the double helix in DNA or hairpin loops in RNA.

• Tertiary Structure: The overall 3D shape, especially important in RNA, which can form complex shapes.

• Ribozyme: An RNA molecule with catalytic activity.

Example: tRNA has a cloverleaf secondary structure and a complex tertiary structure for function in protein synthesis.

Table: Comparison of DNA and RNA

Feature	DNA	RNA
Sugar	Deoxyribose	Ribose
Bases	A, T, G, C	A, U, G, C
Strands	Double-stranded	Single-stranded (usually)
Function	Genetic information storage	Protein synthesis, catalysis (ribozymes)

Additional info: These notes expand on the provided questions by supplying definitions, explanations, and examples for each major topic, ensuring a self-contained study guide for General Biology students.