Ap Bio Unit 2 Questions

Mastering AP Bio Unit 2: A Deep Dive into Cell Structure and Function

AP Biology Unit 2, focusing on cell structure and function, is a cornerstone of the course. This unit lays the groundwork for understanding more complex biological processes later on. Mastering this material is crucial for success on the AP exam. This comprehensive guide will address common AP Bio Unit 2 questions, providing detailed explanations and connecting concepts to build a strong understanding. We’ll explore topics ranging from prokaryotic and eukaryotic cells to membrane transport and cellular respiration. Get ready to conquer cell biology!

I. Prokaryotic vs. Eukaryotic Cells: A Tale of Two Cells

A fundamental concept in Unit 2 is the difference between prokaryotic and eukaryotic cells. This distinction forms the basis for understanding the complexity of life.

Key Differences:

• Prokaryotic Cells: These are simpler cells lacking a membrane-bound nucleus and other membrane-bound organelles. Their DNA is located in a region called the nucleoid. Prokaryotes include bacteria and archaea. Think of them as the "early adopters" of life on Earth.

• Eukaryotic Cells: These cells are significantly more complex, possessing a membrane-bound nucleus containing their DNA and numerous other membrane-bound organelles, each with a specialized function. Eukaryotes encompass protists, fungi, plants, and animals.

Here’s a table summarizing the key differences:

Common AP Exam Questions:

• Compare and contrast the structures and functions of prokaryotic and eukaryotic cells.
• Explain the evolutionary significance of the differences between prokaryotic and eukaryotic cells. (Endosymbiotic theory often plays a role here).
• Identify cellular structures in micrographs or diagrams.

II. Membrane Structure and Function: The Gatekeepers of the Cell

The cell membrane is a dynamic, selectively permeable barrier that regulates what enters and exits the cell. Understanding its structure and function is essential.

Fluid Mosaic Model: The cell membrane is best described by the fluid mosaic model, depicting a fluid bilayer of phospholipids with embedded proteins and other molecules.

• Phospholipids: These amphipathic molecules form a bilayer, with their hydrophilic (water-loving) heads facing outwards and their hydrophobic (water-fearing) tails facing inwards. This arrangement creates a barrier between the cell and its environment.

• Proteins: Membrane proteins have diverse functions, including transport, enzymatic activity, signal transduction, cell adhesion, and intercellular joining. These proteins can be integral (embedded within the membrane) or peripheral (loosely associated with the membrane surface).

• Cholesterol: In animal cells, cholesterol molecules help maintain membrane fluidity.

Membrane Transport: The movement of substances across the cell membrane is crucial for cellular function.

• Passive Transport: This requires no energy input. It includes:

  • Simple Diffusion: Movement of substances down their concentration gradient (high to low).
  • Facilitated Diffusion: Movement of substances down their concentration gradient with the help of transport proteins.
  • Osmosis: Movement of water across a selectively permeable membrane from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration).

• Active Transport: This requires energy input (ATP) and moves substances against their concentration gradient (low to high). Examples include the sodium-potassium pump.

Common AP Exam Questions:

• Explain the fluid mosaic model of the cell membrane.
• Describe the different types of membrane transport and the energy requirements of each.
• Predict the direction of water movement across a selectively permeable membrane under different osmotic conditions (hypotonic, hypertonic, isotonic).
• Relate the structure of the cell membrane to its function in maintaining homeostasis.

III. Cellular Respiration: Powering the Cell

Cellular respiration is the process by which cells break down glucose to produce ATP, the energy currency of the cell. This process is essential for all life.

Stages of Cellular Respiration:

• Glycolysis: Occurs in the cytoplasm and breaks down glucose into pyruvate, producing a small amount of ATP and NADH.

• Pyruvate Oxidation: Pyruvate is converted to acetyl-CoA, producing NADH and releasing carbon dioxide. This occurs in the mitochondrial matrix.

• Krebs Cycle (Citric Acid Cycle): Acetyl-CoA is oxidized, producing ATP, NADH, FADH2, and releasing carbon dioxide. This also takes place in the mitochondrial matrix.

• Electron Transport Chain (ETC) and Oxidative Phosphorylation: Electrons from NADH and FADH2 are passed along a series of electron carriers, generating a proton gradient across the inner mitochondrial membrane. This gradient drives ATP synthesis through chemiosmosis. Oxygen is the final electron acceptor, forming water.

Anaerobic Respiration (Fermentation): In the absence of oxygen, cells can undergo fermentation, producing less ATP than aerobic respiration. There are two main types: lactic acid fermentation and alcoholic fermentation.

Common AP Exam Questions:

• Describe the overall process of cellular respiration, including the inputs, outputs, and location of each stage.
• Explain the role of electron carriers (NADH and FADH2) in cellular respiration.
• Describe the chemiosmotic mechanism of ATP synthesis.
• Compare and contrast aerobic and anaerobic respiration.
• Analyze data related to cellular respiration experiments (e.g., measuring oxygen consumption or carbon dioxide production).

IV. Photosynthesis: Capturing Solar Energy

Photosynthesis is the process by which plants and other photosynthetic organisms convert light energy into chemical energy in the form of glucose.

Stages of Photosynthesis:

• Light-Dependent Reactions: Occur in the thylakoid membranes of chloroplasts. Light energy is absorbed by chlorophyll and other pigments, exciting electrons and leading to the production of ATP and NADPH. Water is split (photolysis), releasing oxygen as a byproduct.

• Light-Independent Reactions (Calvin Cycle): Occur in the stroma of chloroplasts. ATP and NADPH from the light-dependent reactions are used to fix carbon dioxide into glucose.

Common AP Exam Questions:

• Explain the overall process of photosynthesis, including the inputs, outputs, and location of each stage.
• Describe the role of chlorophyll and other pigments in photosynthesis.
• Explain the mechanism of ATP and NADPH synthesis in the light-dependent reactions.
• Describe the Calvin cycle and the role of RuBisCO.
• Compare and contrast photosynthesis and cellular respiration.

V. Cell Communication: Talking to Each Other

Cells need to communicate with each other to coordinate their activities and maintain homeostasis.

Types of Cell Communication:

• Direct Contact: Cells communicate directly through gap junctions (animal cells) or plasmodesmata (plant cells).

• Local Signaling: Includes paracrine signaling (local regulators), synaptic signaling (neurotransmitters), and autocrine signaling (self-stimulation).

• Long-Distance Signaling: Involves hormones, which travel through the bloodstream to reach target cells.

Signal Transduction Pathways: These are pathways that relay signals from the cell surface to the interior of the cell, leading to a cellular response.

Common AP Exam Questions:

• Describe the different types of cell communication.
• Explain the concept of signal transduction pathways.
• Describe the role of second messengers in signal transduction.
• Analyze data related to cell signaling experiments.

VI. The Cytoskeleton: Cell Shape and Movement

The cytoskeleton is a network of protein fibers that provides structural support, maintains cell shape, and facilitates cell movement.

Components of the Cytoskeleton:

• Microtubules: Largest diameter, involved in cell shape, chromosome movement during cell division, and intracellular transport.

• Microfilaments: Smallest diameter, involved in cell shape, muscle contraction, and cytoplasmic streaming.

• Intermediate Filaments: Intermediate diameter, provide structural support and anchor organelles.

Common AP Exam Questions:

• Describe the structure and function of the cytoskeleton.
• Explain the role of microtubules in cell division.
• Describe the role of microfilaments in muscle contraction.

VII. Cell Junctions: Connecting Cells

Cell junctions connect cells together, forming tissues and organs.

Types of Cell Junctions:

• Tight Junctions: Form a watertight seal between cells.

• Desmosomes: Anchor cells together, providing strong adhesion.

• Gap Junctions: Allow direct communication between cells through channels.

Common AP Exam Questions:

• Describe the different types of cell junctions and their functions.
• Explain how cell junctions contribute to tissue integrity.

VIII. Cell Cycle and Cell Division: Growth and Reproduction

The cell cycle is the sequence of events that leads to cell growth and division. Mitosis is the process of nuclear division that produces two genetically identical daughter cells.

Stages of the Cell Cycle:

• Interphase: The cell grows and replicates its DNA.

• Mitosis: Includes prophase, prometaphase, metaphase, anaphase, and telophase.

• Cytokinesis: The cytoplasm divides, producing two daughter cells.

Common AP Exam Questions:

• Describe the stages of the cell cycle and the events that occur during each stage.
• Explain the role of checkpoints in regulating the cell cycle.
• Describe the process of mitosis.
• Compare and contrast mitosis and meiosis.

IX. Conclusion: Building a Solid Foundation

Mastering AP Bio Unit 2 requires a thorough understanding of cell structure, function, and communication. By understanding the interconnections between these topics, you can build a strong foundation for success in the remainder of the course and on the AP exam. Remember to practice problem-solving, utilize diagrams and visualizations, and seek clarification on any confusing concepts. Good luck!