Chapter 2: Chemistry Comes Alive – Study Notes

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This section introduces the foundational concepts of matter and energy, which are essential for understanding biological processes.

Matter: Anything that occupies space and has mass. Exists in three states: solid, liquid, and gas.
Energy: The capacity to do work or put matter into motion. Exists in various forms such as kinetic (energy of motion) and potential (stored energy).
Law of Conservation of Energy: Energy cannot be created or destroyed, only converted from one form to another.
Forms of Energy: Chemical, electrical, mechanical, and radiant energy.
Example: Chemical energy stored in food molecules is converted to kinetic energy during muscle contraction.

Understanding the structure of matter is crucial for grasping how biological molecules interact.

Elements: Substances that cannot be broken down into simpler substances by ordinary chemical means. Examples: carbon, hydrogen, oxygen, nitrogen.
Atoms: The smallest units of elements that retain their properties. Composed of protons, neutrons, and electrons.
Atomic Number: Number of protons in the nucleus.
Mass Number: Sum of protons and neutrons in the nucleus.
Isotopes: Atoms of the same element with different numbers of neutrons.
Radioisotopes: Unstable isotopes that emit radiation as they decay.
Example: Carbon-12 and Carbon-14 are isotopes of carbon.

Matter can be combined in various ways to form molecules and mixtures, which are fundamental to biological systems.

Molecule: Two or more atoms bonded together (e.g., H2O).
Compound: Molecules composed of two or more different elements (e.g., NaCl).
Mixture: Substances physically blended but not chemically combined (e.g., air, blood).
Types of Mixtures: Solutions, colloids, and suspensions.
Example: Blood is a suspension because its components can settle out.

Chemical bonds are forces that hold atoms together in molecules and compounds.

Ionic Bonds: Formed by the transfer of electrons from one atom to another, resulting in charged ions (e.g., NaCl).
Covalent Bonds: Formed by the sharing of electrons between atoms (e.g., H2O).
Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).
Example: Hydrogen bonds are responsible for water's high boiling point.

Chemical reactions involve the making or breaking of bonds between atoms, leading to the formation of new substances.

Types of Reactions:
- Synthesis (Combination): Atoms or molecules combine to form a larger molecule.
- Decomposition: A molecule is broken down into smaller molecules.
- Exchange (Displacement): Bonds are both made and broken.
Factors Influencing Reaction Rates: Temperature, concentration, particle size, and catalysts (e.g., enzymes).
Example: Enzymes speed up biochemical reactions in the body.

Inorganic compounds are essential for life and include water, salts, and acids/bases.

Water: Most abundant inorganic compound; excellent solvent; high heat capacity; participates in chemical reactions.
Salts: Ionic compounds that dissociate in water to form electrolytes (e.g., NaCl).
Acids and Bases: Acids release H+ ions; bases release OH- ions. pH measures hydrogen ion concentration.
pH Scale: Ranges from 0 (acidic) to 14 (basic); 7 is neutral.
Example: Blood pH is tightly regulated around 7.4.

Organic compounds contain carbon and are unique to living systems. They include carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

Lipids

Proteins

Structure: Made of amino acids linked by peptide bonds. Four levels of structure: primary, secondary, tertiary, quaternary.
Functions: Enzymes, structural support, transport, movement, defense.
Enzymes: Biological catalysts that speed up chemical reactions by lowering activation energy.
Example: Hemoglobin transports oxygen in the blood.

Nucleic Acids

Types: DNA and RNA.
Structure: Composed of nucleotides (sugar, phosphate, nitrogenous base).
Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G), Uracil (U in RNA).
Function: Store and transmit genetic information.
Example: DNA contains instructions for protein synthesis.

ATP (adenosine triphosphate) is the primary energy carrier in cells.

Structure: Adenine, ribose, and three phosphate groups.
Function: Provides energy for cellular work by releasing a phosphate group (hydrolysis).
Equation:
Example: Muscle contraction and active transport use ATP.

Type	Building Blocks	Function	Example
Carbohydrates	Monosaccharides	Energy source	Glucose, glycogen
Lipids	Fatty acids, glycerol	Energy storage, membranes	Triglycerides, phospholipids
Proteins	Amino acids	Enzymes, structure, transport	Hemoglobin, enzymes
Nucleic Acids	Nucleotides	Genetic information	DNA, RNA

Enzymes are highly specific and can be regulated by factors such as temperature and pH.
Water's polarity makes it an excellent solvent for ionic and polar substances.
ATP is regenerated from ADP and phosphate during cellular respiration.