Midterm Exam Study Guide: General Biology

This study guide outlines the key topics and concepts for the midterm exam in a General Biology course, focusing on chapters 1 through 8. The exam will test your understanding of cell structure, membrane processes, energy metabolism, and photosynthesis, among other foundational topics.

Exam Structure

• Part 1: Multiple-choice questions (Monday, Oct. 13, 12:15-12:50pm, JTB 100)

  • 50 questions total

  • 8 questions on chapters 1-4 (emphasis on chapter 3 for test 1 topics)

  • 17 questions on chapters 5-8 (emphasis on chapter 5)

• Part 2: Short answer and fill-in-the-blank (Wednesday, Oct. 15, 12:15-12:50pm, JTB 100)

  • Questions will focus on main topics from chapters 3, 4, 5, 7, and 8

  • Be prepared to compare/contrast, draw, and interpret figures

Key Topics and Concepts

Membrane Structure and Processes

Understanding the structure and function of biological membranes is essential for explaining how cells interact with their environment and maintain homeostasis.

• Membrane Structure: Composed primarily of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

• Functions of Membrane Proteins:

  • Transport (channels and carriers)

  • Enzymatic activity

  • Signal transduction

  • Cell-cell recognition

  • Intercellular joining

  • Attachment to cytoskeleton and extracellular matrix

• Membrane Permeability: Selective permeability allows some substances to cross more easily than others.

• Types of Transport:

  • Passive Transport: Movement of substances down their concentration gradient without energy input (e.g., diffusion, facilitated diffusion, osmosis).

  • Active Transport: Movement of substances against their concentration gradient, requiring energy (usually ATP).

  • Bulk Transport: Endocytosis and exocytosis for large molecules or particles.

• Water Balance in Animal and Plant Cells: Osmosis regulates water movement; isotonic, hypertonic, and hypotonic solutions affect cell volume.

• Stages of Cell Signaling: Reception, transduction, and response.

• Types of Receptors: Membrane receptors (ion channel-linked, G protein-coupled, enzyme-linked) and intracellular receptors.

• Example: Epinephrine pathway: Binding of epinephrine to a GPCR results in glycogen breakdown and increased blood sugar levels.

Energy, Enzymes, and ATP

Cells require energy to perform work, which is managed through metabolic pathways involving enzymes and ATP.

• Energy Transformations: Cells convert energy from one form to another (e.g., chemical to mechanical).

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

• Factors Affecting Enzyme Activity: Temperature, pH, substrate concentration, inhibitors, and activators.

• ATP (Adenosine Triphosphate): The primary energy currency of the cell; energy is released by hydrolysis of ATP to ADP and inorganic phosphate.

• ATP Coupling: The use of exergonic reactions to drive endergonic processes in the cell.

• Types of Cellular Work: Mechanical, transport, and chemical work.

• Example: Sodium-potassium pump uses ATP to transport Na+ and K+ against their gradients.

Respiration, Fermentation, and Photosynthesis

These processes are central to how cells obtain and use energy. Understanding their steps, inputs, outputs, and regulation is crucial for biology students.

Respiration

• Overall Equation:

• Main Stages:

  1. Glycolysis

  2. Pyruvate Oxidation

  3. Citric Acid Cycle (Krebs Cycle)

  4. Oxidative Phosphorylation (Electron Transport Chain and Chemiosmosis)

• Inputs and Outputs:

  • Glycolysis: Glucose → 2 Pyruvate, 2 ATP (net), 2 NADH

  • Pyruvate Oxidation: 2 Pyruvate → 2 Acetyl-CoA, 2 CO2, 2 NADH

  • Citric Acid Cycle: 2 Acetyl-CoA → 4 CO2, 2 ATP, 6 NADH, 2 FADH2

  • Oxidative Phosphorylation: NADH and FADH2 donate electrons to the electron transport chain, producing ~26-28 ATP

• ATP Synthesis:

  • Substrate-level phosphorylation: Direct transfer of phosphate to ADP

  • Oxidative phosphorylation: ATP synthesis powered by redox reactions in the electron transport chain

Fermentation

• Occurs in the absence of oxygen

• Types:

  • Lactic acid fermentation: Pyruvate is reduced to lactic acid (e.g., in muscle cells)

  • Alcohol fermentation: Pyruvate is converted to ethanol and CO2 (e.g., in yeast)

• Comparison with Respiration: Fermentation produces much less ATP than aerobic respiration.

Photosynthesis

• Overall Equation:

• Main Stages:

  1. Light Reactions (in thylakoid membranes): Convert solar energy to chemical energy (ATP and NADPH), produce O2

  2. Calvin Cycle (in stroma): Uses ATP and NADPH to convert CO2 to glucose

• Inputs and Outputs of the Calvin Cycle:

  • Inputs: CO2, ATP, NADPH

  • Outputs: G3P (a sugar), ADP, NADP+

  • Number of carbon atoms and phosphate groups: Track the number of carbons and phosphates in each intermediate (see textbook figures for details).

• Photophosphorylation: Light-driven production of ATP during the light reactions.

• Comparison with Respiration: Both involve electron transport chains and chemiosmosis, but in opposite directions (energy capture vs. energy release).

Table: Comparison of Respiration and Photosynthesis

Additional Study Tips

• Review lecture notes, Mastering Biology assignments, and practice figures in the textbook.

• Use provided module guides and outlines to organize your study.

• Practice drawing and labeling key pathways and cycles (e.g., glycolysis, Calvin cycle).

• Be able to compare and contrast similar processes (e.g., fermentation vs. respiration).