General Biology: Study Guide – Foundations, Cells, and Metabolism

Chapter: The Study of Life

Scientific Method

The scientific method is a systematic approach used by scientists to explore observations, answer questions, and test hypotheses.

• Steps of the Scientific Method:

  1. Observation: Gathering information about a phenomenon.

  2. Question: Formulating a question based on observations.

  3. Hypothesis: Proposing a testable explanation.

  4. Experiment: Testing the hypothesis through controlled experiments.

  5. Data Collection: Recording and analyzing results.

  6. Conclusion: Drawing conclusions based on data.

  7. Communication: Sharing results with the scientific community.

• Inductive Reasoning: Making generalizations based on specific observations. Example: Observing that all swans seen are white and concluding all swans are white.

• Deductive Reasoning: Making specific predictions based on general principles or theories. Example: If all mammals have lungs, and a whale is a mammal, then a whale has lungs.

Chapter: Chemical Foundations of Life

Atoms and Elements

All matter is composed of atoms, the smallest units of elements that retain the properties of that element.

• Atom: The basic unit of matter, consisting of protons, neutrons, and electrons.

• Element: A substance that cannot be broken down into simpler substances by chemical means. Each element is defined by its atomic number.

• Atomic Number: The number of protons in the nucleus of an atom; determines the element's identity.

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

• Subatomic Particles:

  • Proton: Positively charged particle in the nucleus.

  • Neutron: Neutral particle in the nucleus.

  • Electron: Negatively charged particle orbiting the nucleus.

Chemical Bonds

• Ionic Bond: Formed when electrons are transferred from one atom to another, resulting in oppositely charged ions.

• Covalent Bond: Formed when two atoms share one or more pairs of electrons.

• Hydrogen Bond: A weak bond between a hydrogen atom covalently bonded to an electronegative atom (like oxygen or nitrogen) and another electronegative atom. These bonds break easily.

• Molecule: Two or more atoms held together by covalent bonds.

Chapter: Macromolecules

Carbon and Organic Compounds

Carbon atoms can form up to four covalent bonds, allowing for a diversity of organic molecules.

• Organic Compound: A compound that contains carbon and is found in living organisms.

• Hydrolysis Reaction: A chemical reaction that breaks bonds between two molecules by the addition of water.

• Fatty Acids: Lipids typically do not have fatty acid tails if they are steroids (e.g., cholesterol).

• Helix: A spiral structure, such as the alpha-helix in proteins.

• Protein Denaturation: The process in which a protein loses its shape and function due to external stress (e.g., heat, pH).

• Monomers:

  • Proteins: Amino acids

  • Nucleic acids: Nucleotides

Chapter: Cell Structure

Cell Theory and Organelles

The Cell Theory is a fundamental concept in biology stating that all living things are composed of cells, and all cells come from pre-existing cells.

• Tenets of Cell Theory:

  1. All living things are composed of one or more cells.

  2. The cell is the basic unit of structure and function in living things.

  3. All cells arise from pre-existing cells.

• Golgi Body: Modifies, sorts, and packages proteins and lipids for storage or transport out of the cell.

• Organelle Descended from Ancient Bacteria: Mitochondria (endosymbiotic theory).

• Cell Wall: Provides structural support and protection in plant cells, fungi, and some prokaryotes.

• Chloroplast: Organelle where photosynthesis occurs; contains chlorophyll, which makes plants appear green.

• Plastids: Group of plant organelles that includes chloroplasts, chromoplasts, and amyloplasts.

• Eukaryotic vs. Prokaryotic Cells: Eukaryotic cells have a nucleus and membrane-bound organelles; prokaryotic cells do not.

• Vacuole: Stores nutrients and waste products; helps maintain turgor pressure in plant cells.

• "Living" Qualities: Growth, reproduction, response to stimuli, metabolism, homeostasis, and adaptation.

Chapter: Structure and Function of Plasma Membranes

Membrane Structure and Transport

The plasma membrane controls the movement of substances into and out of the cell and is composed of a phospholipid bilayer with embedded proteins.

• Fluid Mosaic Model: Describes the plasma membrane as a flexible, dynamic structure with proteins floating in or on the fluid lipid bilayer.

• Transmembrane Proteins: Proteins that span the entire membrane and are involved in transport and signaling.

• Diffusion of Solutes: Movement of molecules from an area of higher concentration to an area of lower concentration.

• Active vs. Passive Transport:

  • Active Transport: Requires energy (ATP) to move substances against their concentration gradient.

  • Passive Transport: Does not require energy; includes diffusion and facilitated diffusion.

• Sodium-Potassium Pump: An example of active transport that moves Na+ out of and K+ into the cell.

• Phagocytosis: "Cell eating"; the process by which a cell engulfs large particles.

• Endocytosis: The process of taking material into the cell by infolding of the cell membrane.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Plant Cell in Solutions:

  • Hypotonic Solution: Water enters the cell; cell becomes turgid.

  • Hypertonic Solution: Water leaves the cell; cell shrinks (plasmolysis).

  • Isotonic Solution: No net movement of water; cell remains the same.

• Facilitated Diffusion: Movement of molecules across a membrane via transport proteins without energy input.

Chapter: Metabolism

Thermodynamics and Chemical Reactions

Metabolism encompasses all chemical reactions in a cell, governed by the laws of thermodynamics.

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

• Second Law of Thermodynamics: Every energy transfer increases the entropy (disorder) of the universe.

• Third Law of Thermodynamics: As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.

• Energy in Chemical Bonds: Chemical bonds store potential energy; breaking bonds releases energy.

• Activation Energy: The minimum amount of energy required to start a chemical reaction.

• Exergonic Reaction: Releases energy; products have less free energy than reactants.

• Endergonic Reaction: Requires energy input; products have more free energy than reactants.

• Enzymes: Biological catalysts that speed up chemical reactions by lowering activation energy.

• Enzyme-Substrate Complex: Temporary association between an enzyme and its substrate(s) during a reaction.

• Oxidation-Reduction (Redox) Reaction: A chemical reaction involving the transfer of electrons from one molecule to another.

  • Oxidation: Loss of electrons.

  • Reduction: Gain of electrons.

Key Equations

• General Chemical Reaction: $\text{Reactants} \rightarrow \text{Products}$

• Free Energy Change: $\Delta G = \Delta H - T\Delta S$ where $\Delta G$ is the change in free energy, $\Delta H$ is the change in enthalpy, $T$ is temperature in Kelvin, and $\Delta S$ is the change in entropy.

• Enzyme-Catalyzed Reaction: $\text{E} + \text{S} \rightleftharpoons \text{ES} \rightarrow \text{E} + \text{P}$ where E = enzyme, S = substrate, ES = enzyme-substrate complex, P = product.