Atoms consist of protons and neutrons in a dense nucleus, surrounded by a cloud of electrons in discrete energy levels.

Chemical behavior arises entirely from electron interactions.

The atomic number represents the number of protons in the nucleus and uniquely defines an element.

The mass number is the total of protons and neutrons in the nucleus.

Relative atomic mass is the weighted average of all naturally occurring isotopes of an element.

Electrons are the only particles that actually move during reactions.

Atoms become ions by gaining or losing electrons to achieve a more stable electron configuration.

A cation forms when an atom loses electrons, resulting in a positive charge.

An anion forms when an atom gains electrons, resulting in a negative charge.

Orbitals are probability regions where electrons are most likely found, rather than fixed paths.

s orbitals hold up to 2 electrons and are spherical.

p orbitals hold up to 6 electrons and create directional bonding, largely determining molecular shape.

d and f orbitals are involved in transition metals and complex bonding behavior.

Valence electrons are electrons in the outermost energy level that participate in bonding.

The periodic table is arranged by increasing atomic number, leading to repeating patterns of electron configuration and chemical behavior.

Each period corresponds to the number of occupied electron shells in an atom.

Elements in the same group have the same number of valence electrons, leading to similar reactivity.

Metals readily lose electrons, form positive ions, are reactive, and are good conductors.

Nonmetals tend to gain or share electrons and form most biological molecules.

Metalloids have intermediate properties between metals and nonmetals and are useful in electronics.

Metallic bonding occurs when positive metal ions share a sea of delocalized electrons, allowing conductivity and malleability.

Lewis diagrams represent valence electrons as dots and shared pairs as lines, allowing prediction of bonding and molecular structure.

Covalent bonding involves the sharing of electron pairs between atoms.

Ionic bonding involves the electrostatic attraction between oppositely charged ions.

Differences in electronegativity cause unequal sharing of electrons, producing polar molecules with partial charges.

Hydrogen bonds are weak intermolecular attractions between δ⁺ hydrogen atoms and electronegative atoms like oxygen or nitrogen.

Cohesion, adhesion, high specific heat, and its ability to act as a universal solvent.

Cohesion allows water molecules to stick together.

Adhesion allows water to stick to other surfaces.

High specific heat stabilizes temperatures, preventing sudden temperature changes.

Water can dissolve polar and ionic substances, allowing biochemical reactions to occur.

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, primarily used for energy and structure.

The monomer of carbohydrates is a monosaccharide, such as glucose.

Lipids are hydrophobic molecules used for long-term energy storage and membrane structure.

Lipids are built from fatty acids and glycerol.

Proteins are polymers of amino acids that perform structural, catalytic, and regulatory functions.

The four levels of protein structure are primary, secondary, tertiary, and quaternary.

A protein's shape determines its function.

Nucleic acids store and transmit genetic information (DNA and RNA).

The monomer of nucleic acids is a nucleotide, which contains a sugar, phosphate, and base.

Enzymes are biological catalysts that lower activation energy by stabilizing transition states, speeding up reactions without being consumed.

The active site is where the substrate binds specifically to the enzyme.

Increasing temperature, increasing concentration, increasing surface area, and adding catalysts.

Redox reactions involve the transfer of electrons and energy.

Oxidation is the loss of electrons, which releases energy.

Reduction is the gain of electrons, which stores energy.

The primary goal of cellular respiration is ATP production.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

Glycolysis breaks glucose into pyruvate in the cytoplasm without oxygen, producing small amounts of ATP.

The Krebs Cycle occurs in the mitochondrial matrix, oxidizes carbon compounds, and loads electron carriers, releasing CO₂.

The Electron Transport Chain occurs on the inner mitochondrial membrane. Electrons pass through protein complexes, pumping protons and driving ATP synthase via chemiosmosis to produce most of the ATP.

Anaerobic respiration occurs without oxygen and produces lactic acid in muscles, leading to fatigue.

Photosynthesis converts light energy into chemical energy stored in glucose, supplying nearly all energy in ecosystems.

The two main stages are the Light Reactions (in the thylakoid) and the Calvin Cycle (in the stroma).

ATP and NADPH are generated during the Light Reactions.

Carbon is fixed into glucose during the Calvin Cycle.

Palisade mesophyll contains many chloroplasts to maximize photosynthesis.

Spongy mesophyll allows for gas exchange within the leaf.

Xylem transports water throughout the plant.

Phloem transports sugars throughout the plant.

Guard cells regulate the opening and closing of stomata.

Energy flows from producers to consumers and decomposers, with only about 10% transferring between levels.

GPP is the total amount of photosynthesis occurring in an ecosystem.

NPP is the energy available to consumers after producers use some for their own respiration.

Human activities like burning fossil fuels, using fertilizers, and deforestation alter biogeochemical cycles.

Electron behavior controls chemistry, chemistry controls biology, and biology controls ecosystems.