Introduction to Biology & Chemistry of Life – Study Notes

Introduction to Biology

Themes & Organization of Biology

Biology is the scientific study of life, encompassing a wide range of themes and organizational levels. Understanding these themes helps explain the complexity and diversity of living organisms.

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

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

• 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, each containing organelles and molecules.

Scientific Method & Scientific Thinking

Steps and Reasoning in Science

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

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

• Hypothesis vs. Theory: A hypothesis is a testable explanation for an observation; a theory is a broader, well-supported explanation.

• Inductive Reasoning: Drawing general conclusions from specific observations.

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

• 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.

Chemistry of Life

Atoms, Elements, and Isotopes

All living things are composed of matter, which consists of elements organized into atoms. Understanding atomic structure is fundamental to biology.

• Atoms: The smallest units of elements, composed of protons, neutrons, and electrons.

• Subatomic Particles: Protons (positive charge), neutrons (neutral), and electrons (negative charge).

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

• Atomic Mass: Sum of protons and neutrons.

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

• Carbon: Has 4 valence electrons, allowing it to form four covalent bonds, making it highly versatile in forming organic molecules.

Example: Carbon-12 and Carbon-14 are isotopes of carbon, differing in neutron number.

Water & Chemical Bonds

Bond Types and Water Properties

Water's unique properties are essential for life and result 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), responsible for cohesion and surface tension.

• High Specific Heat: Water absorbs and releases heat slowly, stabilizing temperatures in organisms and environments.

• Density of Ice: Ice is less dense than liquid water due to hydrogen bonding, allowing it to float and insulate aquatic life.

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

Energy & ATP

Energy Forms and ATP Function

Energy is required for all biological processes. ATP (adenosine triphosphate) is the primary energy carrier in cells.

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

• Kinetic Energy: Energy of motion (e.g., muscle contraction).

• Potential Energy: Stored energy (e.g., chemical bonds in glucose).

• ATP: The cell's energy currency; hydrolysis of ATP to ADP releases energy for cellular work.

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

Example: Muscle contraction uses energy released from ATP hydrolysis.

Biological Macromolecules

Types, Structure, and Function

Macromolecules are large, complex molecules essential for life, including 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); function as enzymes, structural components, and more.

• 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
Nucleic Acid	Nucleotide	Genetic information

Example: Starch (plants) and glycogen (animals) are polysaccharides; glycogen is more highly branched.

Comparison of Fats:

Type	Saturation	Structure
Saturated Fat	No double bonds	Straight chains, solid at room temp
Unsaturated Fat	One or more double bonds	Kinked chains, liquid at room temp

Protein Shape: Determined by amino acid sequence and interactions (hydrogen bonds, ionic bonds, hydrophobic interactions, disulfide bridges).