Unit 1 Study Guide: Introduction to Biology & Chemistry of Life

Themes & Organization of Biology

Emergent Properties and Biological Organization

Biological systems display emergent properties—new characteristics that arise from the interactions and arrangement of parts within a system. Understanding these properties is essential for grasping how complex organisms and ecosystems function.

• Emergent Properties: Characteristics not present at lower levels of organization but arise at higher levels due to interactions among components (e.g., consciousness in the brain, life in a cell).

• Hierarchy of Biological Organization: Life is organized into a series of levels, each building on the previous one: molecule → organelle → cell → tissue → organ → organism → population → community → ecosystem → biosphere.

• Reductionism vs. Systems Biology: Reductionism breaks complex systems into simpler components for study, while systems biology examines interactions within the whole system.

• Negative Feedback Regulation: A process in which a system responds to a change by returning to its original state, maintaining homeostasis (e.g., body temperature regulation).

Example: The heart is made of muscle cells, but the ability to pump blood emerges only when these cells are organized into tissues and organs.

Additional info: Positive feedback amplifies changes (e.g., blood clotting), while negative feedback counteracts them.

Scientific Method & Scientific Thinking

Steps and Reasoning in Scientific Inquiry

The scientific method is a systematic approach to understanding the natural world through observation, hypothesis formation, experimentation, and analysis.

• Steps: Observation → Hypothesis → Prediction → Experiment → Analysis → Conclusion

• Hypothesis vs. Theory: A hypothesis is a testable explanation for an observation; a theory is a broad, well-supported explanation based on extensive evidence.

• Inductive Reasoning: Drawing general conclusions from specific observations (e.g., all observed swans are white, so all swans are white).

• Deductive Reasoning: Making specific predictions based on general principles (e.g., all mammals have hair; this animal is a mammal, so it has hair).

• Controlled Experiments: Experiments in which only one variable is changed at a time, with all others held constant.

Example: Testing whether fertilizer increases plant growth by comparing treated and untreated plants under identical conditions.

Additional info: Scientific laws describe patterns; theories explain them. Not all hypotheses are testable (e.g., supernatural claims).

Chemistry of Life

Atoms, Elements, and Isotopes

All matter is composed of atoms, which consist of subatomic particles: protons, neutrons, and electrons. The arrangement and interactions of these particles determine the properties of elements and molecules essential for life.

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

• Atomic Mass: Sum of protons and neutrons in the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons (e.g., Carbon-12 vs. Carbon-14).

• Electrons: Negatively charged particles in orbitals; do not significantly affect atomic mass.

• Carbon: Has four valence electrons, allowing it to form up to four covalent bonds—making it highly versatile in forming organic molecules.

Example: Radioactive isotopes are used in medical imaging and dating fossils.

Additional info: The periodic table arranges elements by atomic number and properties.

Water & Chemical Bonds

Types of Bonds and Properties of Water

Chemical bonds hold atoms together in molecules. Water’s unique properties arise from its structure and the hydrogen bonds between molecules.

• Covalent Bonds: Atoms share electrons (e.g., H2O, CH4).

• Ionic Bonds: Atoms transfer electrons, forming charged ions (e.g., NaCl).

• Hydrogen Bonds: Weak attractions between a hydrogen atom in one molecule and an electronegative atom (like oxygen) in another; responsible for water’s cohesion and surface tension.

• High Specific Heat: Water absorbs or releases large amounts of heat with little temperature change, stabilizing environments.

• Density of Ice: Ice is less dense than liquid water because hydrogen bonds form a lattice, causing it to float.

Example: Sweating cools the body because water absorbs heat as it evaporates (evaporative cooling).

Additional info: Water’s polarity makes it an excellent solvent for ionic and polar substances.

Energy & ATP

Forms of Energy and ATP Function

Energy is the capacity to do work. In biological systems, energy transformations are governed by the laws of thermodynamics, and ATP serves as the main energy currency of the cell.

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

• Kinetic Energy: Energy of motion (e.g., moving molecules).

• Potential Energy: Stored energy due to position or structure (e.g., chemical bonds).

• ATP (Adenosine Triphosphate): Stores energy in its phosphate bonds; hydrolysis of ATP to ADP releases energy for cellular processes.

$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy}$

Example: Muscle contraction and active transport use energy released from ATP hydrolysis.

Additional info: ATP consists of adenine, ribose, and three phosphate groups; the third phosphate bond is high-energy.

Biological Macromolecules

Structure and Function of Major Macromolecules

Living organisms are built from four classes of macromolecules: carbohydrates, lipids, proteins, and nucleic acids. Each class has distinct structures and functions essential for life.

• Carbohydrates: Serve as energy sources (e.g., glucose) and structural materials (e.g., cellulose).

• Lipids: Hydrophobic molecules (e.g., fats, oils, phospholipids); not true polymers; store energy and form membranes.

• Proteins: Made of amino acids; have four levels of structure (primary, secondary, tertiary, quaternary); function as enzymes, structural components, and more.

• Nucleic Acids: DNA and RNA store and transmit genetic information; DNA is double-stranded, RNA is usually single-stranded.

• Dehydration Synthesis: Builds polymers by removing water; hydrolysis breaks them down by adding water.

Macromolecule	Monomer	Function
Carbohydrate	Monosaccharide	Energy, structure
Lipid	Fatty acid & glycerol	Energy storage, membranes
Protein	Amino acid	Enzymes, structure, transport
Nucleic Acid	Nucleotide	Genetic information

Example: Starch (plants) and glycogen (animals) are storage polysaccharides; cellulose provides plant cell wall structure.

Additional info: Saturated fats have no double bonds (solid at room temp); unsaturated fats have double bonds (liquid at room temp). Protein shape is determined by amino acid sequence and interactions.