Introduction to Biology & Chemistry of Life – Study Notes

Introduction to Biology

Themes & Organization of Biology

Biology is the scientific study of life, organized into hierarchical levels that reflect increasing complexity. Understanding these levels and the emergent properties that arise from them is fundamental to the study of living systems.

• Emergent Properties: New characteristics that arise at each level of organization due to interactions among components. For example, life emerges at the level of the cell, not in isolated molecules.

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

• Hierarchy of Biological Organization:

  1. Biosphere

  2. Ecosystem

  3. Communities

  4. Populations

  5. Organisms

  6. Organs

  7. Tissues

  8. Cells

  9. Organelles

  10. Molecules

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

Example: The heart (organ) is made of muscle tissue, which is composed of muscle cells, which contain organelles and molecules. The function of the heart emerges from the interaction of these parts.

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

Scientific Method & Scientific Thinking

Steps of the Scientific Method

The scientific method is a systematic approach to inquiry, ensuring that scientific investigations are logical and reproducible.

• Observation: Gathering information about phenomena.

• 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 from the experiment.

• Conclusion: Determining whether the results support or refute the hypothesis.

• Hypotheses vs. Theories: A hypothesis is a specific, testable statement; a theory is a broad explanation supported by extensive evidence.

• Inductive Reasoning: Drawing general conclusions from specific observations.

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

• Controlled Experiments: Experiments in which only one variable is changed at a time.

Example: Testing whether fertilizer increases plant growth by comparing treated and untreated plants (controlled variable: fertilizer).

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 are the smallest units of elements. Understanding atomic structure is essential for studying biological molecules.

• Atoms: Consist of protons (positive), neutrons (neutral), and electrons (negative).

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

• Atomic Mass: Sum of protons and neutrons.

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

• Carbon: Has 6 protons and typically 6 neutrons; forms four covalent bonds, making it versatile in forming organic molecules.

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

Additional info: Electrons determine chemical behavior but do not significantly affect atomic mass.

Water & Chemical Bonds

Types of Chemical Bonds and Properties of Water

Water's unique properties are critical for life and arise from its molecular structure and bonding.

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

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

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).

• Cohesion: Water molecules stick together due to hydrogen bonding.

• 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 structure, causing it to float.

Example: Sweating cools the body because water absorbs heat as it evaporates (high heat of vaporization).

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

Energy & ATP

Energy in Biological Systems

Energy is fundamental to all biological processes. Cells use ATP to store and transfer energy for cellular work.

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

• Kinetic Energy: Energy of motion.

• Potential Energy: Stored energy due to position or structure.

• ATP (Adenosine Triphosphate): The main energy currency of the cell. Hydrolysis of ATP to ADP releases energy for cellular processes.

$\mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i} + \text{energy}$

• ATP Structure: Adenine base, ribose sugar, and three phosphate groups.

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

Additional info: ADP (adenosine diphosphate) has less energy than ATP because it has one fewer phosphate group.

Biological Macromolecules

Types and Functions of Macromolecules

Macromolecules are large, complex molecules essential for life. They include carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates: Provide energy (e.g., glucose) and structural support (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); perform diverse functions (enzymes, transport, structure).

• Nucleic Acids: DNA and RNA; store and transmit genetic information.

• Dehydration Synthesis: Builds polymers by removing water.

• Hydrolysis: Breaks polymers into monomers 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

• Saturated vs. Unsaturated Fats: Saturated fats have no double bonds (solid at room temp); unsaturated fats have one or more double bonds (liquid at room temp).

• Protein Shape: Determined by amino acid sequence and interactions; crucial for function.

Example: Glycogen (animal storage) is more highly branched than starch (plant storage).

Additional info: Not all lipids are polymers because they are not made from repeating monomer units.