General Biology I: Study Guide for Exam 1 (Chapters 1-5)

Chapter 1 – Themes of Biology and Scientific Method

Characteristics of Life

Biology is the study of living organisms and their interactions with the environment. All living things share certain characteristics that distinguish them from non-living matter.

• Order: Living things are organized and structured.

• Regulation: Organisms maintain stable internal conditions (homeostasis).

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Energy Processing: Living things obtain and use energy.

• Response to Environment: Organisms respond to environmental stimuli.

• Reproduction: Living things reproduce, passing genetic information to offspring.

• Evolutionary Adaptation: Populations evolve over generations.

Example: A bacterium reproducing by binary fission demonstrates both reproduction and energy processing.

Emergent Properties

Emergent properties arise when components interact to form more complex systems. These properties are not present in the individual parts but emerge at higher levels of organization.

• Example: A functioning heart (organ) can pump blood, but individual heart cells cannot.

• Example: Consciousness emerges from the interactions of neurons in the brain.

Biological Organization

Life is organized in a hierarchy from the biosphere to molecules:

• Biosphere: All life on Earth and all places where life exists.

• Ecosystems: All living things in a particular area, plus nonliving components.

• Communities: All organisms in an ecosystem.

• Populations: All individuals of a species in a specific area.

• Organisms: Individual living things.

• Organs and Organ Systems: Body parts with specific functions.

• Tissues: Groups of similar cells performing a function.

• Cells: Basic unit of life.

• Organelles: Functional components within cells.

• Molecules: Chemical structures consisting of two or more atoms.

Scientific Method

The scientific method is a systematic approach to understanding the natural world.

• Observation: Gathering information about phenomena.

• Question: Asking questions about observations.

• Hypothesis: A testable explanation for an observation.

• Prediction: What you expect if the hypothesis is correct.

• Experiment: Testing the hypothesis under controlled conditions.

• Analysis: Interpreting data to draw conclusions.

• Conclusion: Accepting, rejecting, or modifying the hypothesis.

Hypothesis: A proposed explanation that is testable and falsifiable. A useful hypothesis must be able to (1) explain observations and (2) make predictions.

Experimental Design

• Experimental Group: Receives the treatment.

• Control Group: Does not receive the treatment; used for comparison.

• Variables:

  • Independent Variable: The factor that is changed or manipulated.

  • Dependent Variable: The factor that is measured or observed.

• Controlling Variables: Keeping all other factors constant to ensure valid results.

Example: In a study testing the effect of sweetener on mice, the amount of sweetener is the independent variable, and the health outcome is the dependent variable. The control group receives no sweetener.

Energy and Matter in Ecosystems

• Energy: Flows through ecosystems (usually enters as sunlight and exits as heat).

• Matter: Cycles within ecosystems (e.g., carbon, nitrogen cycles).

Chapter 2 – Chemistry of Life and Properties of Water

Chemical Reactions and Conservation of Matter

Chemical reactions involve the rearrangement of atoms to form new substances. Matter is conserved; atoms are neither created nor destroyed.

• Balanced Equation Example:

$4\text{NH}_3 + 5\text{O}_2 \rightarrow 4\text{NO} + 6\text{H}_2\text{O}$

• Reactants: Starting substances in a reaction.

• Products: Substances formed by the reaction.

Atoms, Ions, and the Periodic Table

• Atom: Smallest unit of matter, composed of protons, neutrons, and electrons.

• Isotopes: Atoms of the same element with different numbers of neutrons (e.g., carbon-13 and carbon-14).

• Ions: Atoms or molecules with a net electric charge (cations are positive, anions are negative).

• Periodic Table: Organizes elements by atomic number and properties. The 'Big 4' elements in living things: C, H, O, N.

Electron Shells and Chemical Bonds

• Electron Shells: Electrons occupy shells around the nucleus. The first shell holds up to 2 electrons, the second up to 8, the third up to 18.

• Valence Electrons: Electrons in the outermost shell; determine chemical reactivity.

• Types of Bonds:

  • Covalent: Atoms share electrons (strongest in water).

  • Ionic: Transfer of electrons from one atom to another.

  • Hydrogen: Weak attraction between a hydrogen atom and an electronegative atom.

• Electronegativity: The ability of an atom to attract electrons. Oxygen is highly electronegative.

• Polar vs. Nonpolar Covalent Bonds: Polar bonds have unequal sharing of electrons; nonpolar bonds have equal sharing.

Properties of Water

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature change.

• Ice Floats: Solid water is less dense than liquid water.

• Universal Solvent: Water dissolves many substances, especially polar molecules.

• Hydrophobic vs. Hydrophilic: Hydrophobic substances repel water; hydrophilic substances attract water.

Acids, Bases, and pH

• Acid: Substance that increases H+ concentration.

• Base: Substance that reduces H+ concentration.

• pH Scale: Measures acidity or basicity; ranges from 0 (most acidic) to 14 (most basic).

$\text{pH} = -\log_{10}[\text{H}^+]$

$[\text{H}^+] = 10^{-\text{pH}}$

• A solution with pH 3 has $[\text{H}^+] = 1 \times 10^{-3}$ M.

• A solution with pH 13 has $[\text{H}^+] = 1 \times 10^{-13}$ M.

Chapter 3 – Carbon and the Diversity of Biological Macromolecules

Functional Groups and Carbon Chemistry

• Functional Groups: Groups of atoms that affect molecular function (e.g., hydroxyl, carboxyl, amino, phosphate).

• Valence Electrons: Carbon has 4 valence electrons, allowing it to form diverse molecules.

Macromolecules

• Carbohydrates: Sugars and polymers of sugars (e.g., glucose, starch).

• Lipids: Fats, phospholipids, steroids; hydrophobic.

• Proteins: Polymers of amino acids; perform many cellular functions.

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

Protein Structure

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Alpha helices and beta sheets (hydrogen bonding).

• Tertiary Structure: 3D folding of a single polypeptide.

• Quaternary Structure: Association of multiple polypeptides.

Nucleic Acids and DNA Structure

• DNA: Double helix, antiparallel strands, 5' and 3' ends.

• RNA: Usually single-stranded, contains ribose sugar.

• Nucleotides: Building blocks of nucleic acids; consist of a phosphate group, sugar, and nitrogenous base.

Example: The two strands of DNA are antiparallel, meaning one runs 5' to 3' and the other 3' to 5'.

Genetic Diversity

• The number of possible DNA or amino acid sequences increases exponentially with sequence length.

Example: For DNA with 8 bases, there are $4^8$ possible sequences.

Carbohydrates and Energy Storage

• Starch: Energy storage in plants.

• Cellulose: Structural component in plant cell walls; most abundant organic compound on Earth.

Additional info:

• Some content inferred from standard General Biology I curriculum to provide context and completeness.