IB Bio: Unit 2 Test

Key Concepts and Test Preparation

  • Test Structure

    • Approximately 45-50 marks total

    • Breakdown: 20 multiple choice, roughly 10 database (short answer), and 21 short answer questions

  • Cell Types

    • Eukaryotic Cells:

    • Defined by the presence of a nucleus and membrane-bound organelles.

    • Ribosomes: 80s type.

    • Examples include plant cells and animal cells.

    • Prokaryotic Cells:

    • Lacks a nucleus and membrane-bound organelles.

    • Ribosomes: 70s type.

    • Examples include bacteria and archaea.

    • Comparison: Focus on structural differences and functions of various organelles within each type.

  • Cell Environment and Solutions

    • Understand hydrophilic (water-attracting) vs. hydrophobic (water-repelling).

    • Types of solutions:

    • Hypertonic: Water moves out of the cell, causing it to shrink.

    • Hypotonic: Water moves into the cell, causing it to swell.

    • Isotonic: Cell remains the same; equilibrium is achieved.

    • Osmotic Pressure: The pressure required to prevent the flow of a solvent across a semipermeable membrane.

  • Cell Growth and Division

    • Importance of the surface area to volume ratio in cell size.

    • Consequences of high volume with low surface area: diffusion becomes inefficient, making nutrient and waste transport difficult.

  • Cell Membrane Models

    • Understanding the Fluid Mosaic Model: Describes the cell membrane structure containing various proteins embedded within a phospholipid bilayer.

    • Refer to the Protein Sandwich Theory (wrong) and experiments that led to the current understanding of the cell membrane's structure (e.g., milliliter experiment).

    • Types of Transport:

    • Passive Transport (no energy required):

      • Simple diffusion: Movement from high to low concentration without help.

      • Facilitated diffusion: Requires specific transport proteins (e.g., protein channels and carriers).

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

    • Active Transport (requires energy, ATP):

      • Primary: Direct use of ATP for transport.

      • Secondary: Indirect use of energy, often using gradients created by primary active transport.

      • Bulk Transport:

      • Endocytosis: Bringing substances into the cell (includes phagocytosis - cell eating, and pinocytosis - cell drinking).

      • Exocytosis: Expelling substances from the cell.

  • Cell Specialization and Differentiation

    • All body cells contain the same DNA; specialized functions arise through gene expression.

    • Understanding the role of stem cells:

    • Totipotent: Can become any cell type.

    • Pluripotent: Can become almost any cell type but not all.

    • Multipotent: Can develop into a limited number of cell types.

    • Unipotent: Can only produce one type of cell.

    • Importance of morphogens in differentiation pathways.

  • Data Interpretation and Analysis

    • Read scientific explanations, titles, and headers in provided data tables/charts carefully.

    • Understand margin of error and present ranges for data.

    • Ability to perform and explain percent change.

    • Compare control and experimental groups effectively.

  • Cholesterol Role in Cell Membrane

    • Impacts fluidity and stability of cell membranes, especially during physical activity (warming up).

    • Importance of endosymbiosis in the evolution of eukaryotic cells, citing examples such as mitochondria and chloroplasts.

  • Preparation and Practice

    • Utilize the cognitive practice test; focus on understanding rather than rote memorization.

    • Bring necessary tools: ruler, calculator, and ensure understanding of data interpretation skills.

    • Address potential queries regarding test format and content before the exam date.

  • Conclusion

    • Heavy focus on cell specialization, membrane transport mechanisms, and differences between prokaryotic and eukaryotic cells for the test.