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

Introduction to Biology

Themes & Organization of Biology

Biology is the scientific study of life, organized around several unifying themes that help explain the complexity of living systems.

• Emergent Properties: New characteristics arise at each level of biological organization due to interactions among components. For example, a cell exhibits properties not found in its individual molecules.

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

• Hierarchy of Biological Organization: Life is structured in a hierarchy: molecule → organelle → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere.

• Negative Feedback Regulation: Biological systems maintain homeostasis through negative feedback, where a change triggers a response that counteracts the initial change (e.g., body temperature regulation).

Example: In an ecosystem, the interaction between plants, animals, and microbes leads to nutrient cycling, an emergent property not present in individual organisms.

Scientific Method & Scientific Thinking

Steps of the Scientific Method

The scientific method is a systematic approach to understanding natural phenomena.

• Observation: Gathering information about the natural world.

• Hypothesis: A testable explanation for an observation.

• Prediction: A logical outcome expected if the hypothesis is correct.

• Experiment: Testing the prediction under controlled conditions.

• Analysis: Interpreting data to determine if it supports the hypothesis.

• Conclusion: Summarizing findings and revising hypotheses as needed.

Key Concepts in Scientific Thinking

• Hypotheses vs. Theories: A hypothesis is a specific, testable explanation; a theory is a broad, well-supported explanation for a wide range of observations.

• Inductive Reasoning: Drawing general conclusions from specific observations.

• Deductive Reasoning: Making specific predictions based on general principles.

• Controlled Experiments: Experiments that manipulate one variable while keeping others constant to test a hypothesis.

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

Chemistry of Life

Atoms and Subatomic Particles

All matter is composed of atoms, which consist of subatomic particles.

• Protons: Positively charged particles in the nucleus; determine atomic number.

• Neutrons: Neutral particles in the nucleus; contribute to atomic mass.

• Electrons: Negatively charged particles orbiting the nucleus; involved in chemical bonding.

Atomic Number, Atomic Mass, and Isotopes

• Atomic Number (Z): Number of protons in an atom.

• Atomic Mass (A): Total number of protons and neutrons.

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

Example: Carbon-12 and Carbon-14 are isotopes; both have 6 protons, but different numbers of neutrons.

Water & Chemical Bonds

Types of Chemical Bonds

• Covalent Bonds: Atoms share electrons; strong and common in biological molecules.

• Ionic Bonds: Atoms transfer electrons, forming charged ions that attract each other.

• Hydrogen Bonds: Weak attractions between a hydrogen atom (bonded to O or N) and another electronegative atom; crucial for water's properties.

Properties of Water

• Cohesion: Water molecules stick together due to hydrogen bonding, enabling 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 ice to float.

• Polarity: Water is a polar molecule, with partial positive and negative charges, allowing it to dissolve many substances.

Example: Sweating cools the body because water absorbs heat as it evaporates, utilizing water's high heat of vaporization.

Energy & ATP

Forms of Energy

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

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

ATP: The Energy Currency of the Cell

• Adenosine Triphosphate (ATP): A molecule that stores and transfers energy in cells.

• ATP Hydrolysis: Breaking the terminal phosphate bond of ATP releases energy: $\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy}$

• ATP vs. ADP: ATP has more stored energy than ADP due to its three phosphate groups.

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

Biological Macromolecules

Major Classes of Macromolecules

• Carbohydrates: Sugars and polymers of sugars; provide energy (e.g., glucose) and structural support (e.g., cellulose).

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

• Proteins: Polymers of amino acids; perform diverse functions including catalysis (enzymes), structure, and transport. Four levels of structure: primary, secondary, tertiary, quaternary.

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

Polymer Formation and Breakdown

• Dehydration Synthesis: Monomers join to form polymers by removing water.

• Hydrolysis: Polymers are broken down into monomers by adding water.

Comparison of Saturated and Unsaturated Fats

Property	Saturated Fats	Unsaturated Fats
Bond Type	Single bonds only	One or more double bonds
Structure	Straight chains	Kinked chains
State at Room Temp	Solid	Liquid
Source	Animal fats (e.g., butter)	Plant oils (e.g., olive oil)

Protein Structure Determinants

• Primary Structure: Sequence of amino acids.

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

• Tertiary Structure: Overall 3D shape due to interactions among side chains.

• Quaternary Structure: Association of multiple polypeptide chains.

Example: Hemoglobin's function depends on its quaternary structure of four polypeptide subunits.

Additional info: These notes expand on the study guide by providing definitions, examples, and a comparison table for fats, as well as a LaTeX-formatted equation for ATP hydrolysis.