General Biology Exam Review: Key Concepts and Practice Questions

Test 1 Topics: The Chemical Context of Life, Water and Life, Biological Molecules, and Cell Structure

Atomic Structure and Elements

Atoms are the fundamental units of matter, composed of protons, neutrons, and electrons. The arrangement of electrons in shells determines an atom's chemical properties and reactivity.

• Valence Electrons: Electrons in the outermost shell; determine bonding behavior.

• Major Elements in Living Organisms: Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N) are the most abundant elements in biological systems.

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

Example: Oxygen has 8 protons and typically 8 neutrons, but isotopes like O-18 have 10 neutrons.

Chemical Bonds and Interactions

Chemical bonds hold atoms together in molecules. The main types are covalent, ionic, and hydrogen bonds.

• Covalent Bonds: Atoms share electrons; can be single, double, or triple bonds.

• Ionic Bonds: Transfer of electrons from one atom to another, forming charged ions.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., O or N).

Example: Water molecules are held together by hydrogen bonds, giving water its unique properties.

Properties of Water

Water is essential for life due to its polarity and ability to form hydrogen bonds.

• Cohesion and Adhesion: Water molecules stick to each other and to other substances.

• High Specific Heat: Water resists temperature changes, stabilizing environments.

• Solvent Properties: Water dissolves many substances, facilitating chemical reactions.

Acids, Bases, and pH

The pH scale measures the concentration of hydrogen ions ($[H^+]$) in a solution.

• Acid: Increases $[H^+]$ in solution; pH < 7.

• Base: Decreases $[H^+]$ in solution; pH > 7.

• pH Calculation: $pH = -\log_{10}[H^+]$

Example: If $[H^+] = 10^{-7}$ M, then $pH = 7$.

Characteristics of Life

• Life is based on carbon-containing molecules.

• Reactions occur in aqueous (water-based) environments.

• Organic molecules are primarily composed of C, H, O, and N.

Macromolecules

Biological macromolecules include carbohydrates, lipids, proteins, and nucleic acids.

• Proteins: Polymers of amino acids; structure determined by sequence and interactions.

• Carbohydrates: Sugars and polymers of sugars; energy storage and structural roles.

• Lipids: Hydrophobic molecules; include fats, phospholipids, and steroids.

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

Test 2 Topics: Membrane Structure, Cell Components, and Protein Structure

Membrane Structure and Function

The plasma membrane is described by the fluid mosaic model.

• Fluid Mosaic Model: Membrane is a mosaic of proteins floating in or on a fluid bilayer of phospholipids.

• Phospholipid Bilayer: Hydrophilic heads face outward; hydrophobic tails face inward.

• Membrane Proteins: Integral (span the membrane) and peripheral (attached to surface).

Endomembrane System

The endomembrane system includes organelles that work together to modify, package, and transport lipids and proteins.

• Components: Nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vesicles, and plasma membrane.

• Function: Synthesis and transport of proteins and lipids.

Protein Structure

Proteins have four levels of structure:

• Primary: Sequence of amino acids.

• Secondary: Local folding (alpha helices, beta sheets).

• Tertiary: 3D shape formed by interactions among R groups.

• Quaternary: Association of multiple polypeptide chains.

Example: Hemoglobin has quaternary structure with four polypeptide subunits.

Exam 2 Topics: Metabolism, Cellular Respiration, and Photosynthesis

Metabolic Pathways

Metabolism is the sum of all chemical reactions in a cell, organized into metabolic pathways.

• Catabolic Pathways: Break down molecules, releasing energy (e.g., cellular respiration).

• Anabolic Pathways: Build complex molecules, consuming energy (e.g., protein synthesis).

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

Cellular Respiration

Cellular respiration is the process by which cells extract energy from glucose.

• Stages: Glycolysis, Citric Acid Cycle (Krebs Cycle), Electron Transport Chain.

• Electron Carriers: NADH and FADH2 transfer electrons to the electron transport chain.

• ATP: Main energy currency of the cell.

Photosynthesis

Photosynthesis converts light energy into chemical energy in plants, algae, and some bacteria.

• Light Reactions: Capture light energy to produce ATP and NADPH.

• Calvin Cycle: Uses ATP and NADPH to synthesize sugars from CO2.

• Chlorophyll: Main pigment involved in capturing light energy.

Gene Expression and Molecular Biology

Gene expression involves transcription (DNA to RNA) and translation (RNA to protein).

• Transcription: Synthesis of RNA from a DNA template.

• Translation: Synthesis of protein from an mRNA template.

• Genetic Code: Specifies which amino acids are added during protein synthesis.

Key Tables

Bond Type	Strength	Example
Covalent	Strong	H2O, CH4
Ionic	Moderate	NaCl
Hydrogen	Weak	Between water molecules

Macromolecule	Monomer	Function
Carbohydrate	Monosaccharide	Energy storage, structure
Lipid	Fatty acid, glycerol	Energy storage, membranes
Protein	Amino acid	Catalysis, structure, transport
Nucleic Acid	Nucleotide	Genetic information

Additional info:

• Some questions reference specific processes (e.g., equilibrium, enzyme function, and gene expression) that are foundational to multiple chapters in General Biology.

• Understanding the structure and function of biological molecules is essential for grasping metabolism, cell structure, and genetics.