General Biology Study Guide: Life, Chemistry, Water, Acids & Bases, and Macromolecules

Life and Its Chemistry

Fundamental Characteristics of Life

Understanding what defines life is essential in biology. Life is characterized by several fundamental properties that distinguish living organisms from non-living matter.

• Order: Living things exhibit complex organization.

• Regulation: Homeostasis maintains stable internal conditions.

• Growth and Development: Organisms grow and develop according to genetic instructions.

• Energy Processing: Living things acquire and use energy.

• Response to Environment: Organisms respond to stimuli.

• Reproduction: Life reproduces itself.

• Evolutionary Adaptation: Populations evolve over generations.

Scientific Theory and Hypothesis

Science relies on systematic investigation and explanation of natural phenomena.

• Scientific Theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence and repeatedly tested.

• Hypothesis: A testable statement or prediction about a natural phenomenon.

• Spontaneous Generation: The disproven idea that life can arise from non-living matter.

• Central Dogma of Biology: Describes the flow of genetic information: DNA → RNA → Protein.

Atoms and Subatomic Particles

Atoms are the basic units of matter, composed of subatomic particles with distinct properties.

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

• Atomic Number: Number of protons in an atom; defines the element.

• Mass Number: Sum of protons and neutrons.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Electron Configuration: Arrangement of electrons determines chemical properties.

Elements Essential to Life

Life depends on a small subset of elements, with a few making up the majority of living matter.

• Major Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) make up ~96% of living matter.

• Trace Elements: Required in small amounts (e.g., iron, iodine).

Covalent Bonds and Molecules

Covalent bonds are strong chemical bonds formed by the sharing of electron pairs between atoms.

• Single Covalent Bond: Sharing one pair of electrons.

• Double Covalent Bond: Sharing two pairs of electrons.

• Triple Covalent Bond: Sharing three pairs of electrons.

• Polar Covalent Bond: Electrons are shared unequally, leading to partial charges.

• Nonpolar Covalent Bond: Electrons are shared equally.

• Valence: Number of covalent bonds an atom can form, typically determined by the number of unpaired electrons in the valence shell.

Example: Water (H2O) has polar covalent bonds; methane (CH4) has nonpolar covalent bonds.

Water

Structure and Properties of Water

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

• Polarity: Water molecules have a partial positive charge on hydrogen and a partial negative charge on oxygen.

• Hydrogen Bonds: Weak attractions between the hydrogen atom of one water molecule and the oxygen atom of another.

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature changes.

• Solvent Properties: Water dissolves many substances due to its polarity.

Example: Water's ability to dissolve salts and sugars makes it an excellent medium for biological reactions.

Hydrogen Bonds in Water

• Each water molecule can form up to four hydrogen bonds with neighboring water molecules.

• Hydrogen bonds are responsible for water's high boiling point and surface tension.

Hydrophilic vs. Hydrophobic Substances

• Hydrophilic: Substances that interact well with water (e.g., salts, sugars).

• Hydrophobic: Substances that do not interact well with water (e.g., oils, fats).

Water as a Solvent

• Water's polarity allows it to dissolve ionic and polar substances.

• Nonpolar molecules do not dissolve well in water.

Predicting Polarity

• Organic molecules with many polar bonds (O-H, N-H) are likely to be polar.

• Nonpolar molecules have mostly C-H or C-C bonds.

Acids and Bases

Definitions and Properties

Acids and bases are important in biological systems for maintaining pH and facilitating chemical reactions.

• Acid: Substance that donates protons (H+).

• Base: Substance that accepts protons or donates hydroxide ions (OH-).

• pH Scale: Measures the concentration of H+ ions in solution.

Equation:

$\text{pH} = -\log_{10}[\text{H}^+]$

• Low pH (0-6): Acidic

• pH 7: Neutral

• High pH (8-14): Basic

Acid-Base Reactions

• Acids increase H+ concentration; bases decrease it.

• When acids lose a proton, they become negatively charged; when bases gain a proton, they become positively charged.

Macromolecules

Monomers and Polymers

Biological macromolecules are large molecules made by joining smaller units called monomers.

• Monomer: Small, repeating unit (e.g., glucose, amino acid, nucleotide).

• Polymer: Large molecule made of many monomers (e.g., starch, protein, DNA).

• Polymerization: Process of joining monomers to form polymers.

• Dehydration Synthesis: Reaction that links monomers by removing water.

Example: Proteins are polymers of amino acids; nucleic acids are polymers of nucleotides.

Table: Comparison of Covalent Bonds in Carbon Compounds

Compound	Type of Covalent Bond	Number of Bonds
CO	Triple Bond	3
CO2	Double Bond	2 (each C=O)
CH2	Single Bond	2 (C-H)

Additional info:

• Some context and definitions have been expanded for clarity and completeness.

• Examples and equations have been added to support understanding.