IB Bio: Unit 2- Cell Specialization and Differentiation

  • Introduction to Cell Specialization and Differentiation

    • Cells in an organism have the same DNA but differentiate into various types with distinct functions.

    • Key Terms:

    • Differentiation: Process where a stem cell becomes specialized.

    • Zygote: Fertilized egg that is totipotent, meaning it can develop into any cell type.

    • Pluripotent Stem Cells: Cells that can develop into almost any cell type (e.g., muscle, nerve, etc.).

    • Multipotent Stem Cells: Cells that are limited to becoming a few different cell types (e.g., blood stem cells can become red/white blood cells or platelets).

    • Unipotent Cells: Cells that can only differentiate into one cell type.

  • Role of Morphogens in Differentiation

    • Morphogens are signaling molecules that influence the fate of cells based on their concentration at various regions within the embryo.

    • This chemical gradient determines the path of differentiation for neighboring cells.

  • Drivers of Cell Division

    • Cells divide due to size constraints; as cells grow, a degree of surface area to volume ratio becomes inefficient for nutrient uptake and waste removal, leading to division.

    • Dividing results in two daughter cells: one retains stem cell properties and the other becomes a specialized cell.

  • Adaptation of Different Cell Types

    • Red Blood Cells: Adapted for oxygen transport with high surface area and flexibility to squeeze through capillaries.

    • Microvilli: Projections that increase surface area for nutrient absorption, found in the intestines.

    • Kidney Cells: Cuboidal shape forming tight junctions preventing leakage.

  • Types of Lung Cells

    • Type 1 Pneumocytes: Involved in gas exchange; thin for efficient diffusion.

    • Injury to these cells leads to permanent damage (e.g., from smoking).

    • Type 2 Pneumocytes: Produce surfactant to lower surface tension, preventing alveolar collapse and aiding in gas exchange.

    • Can regenerate if damaged.

  • Muscle Tissue Types

    • Smooth Muscle: Involuntary control, found in organs like the intestines and can contract regardless of body position.

    • Cardiac Muscle: Involuntary, striated muscle found in the heart, able to contract autonomously.

    • Skeletal Muscle: Voluntary control, striated, attached to bones by tendons, responsible for movement.

  • Comparative Anatomy of Sperm and Egg

    • Sperm Cells: Streamlined for speed with flagellum for movement; produced in large quantities throughout life.

    • Egg Cells: Larger and non-motile, contain necessary organelles and substances for early development.

    • The egg has a chemical barrier to prevent multiple sperm from fertilizing it.

  • Conclusion

    • Cell specialization allows for diverse functions critical to organism survival and efficiency.

    • Understanding these processes is essential in fields like developmental biology, medicine, and genetics.

    • Review Questions:

    • What are the types of stem cells, and how do they differ?

    • How does the structure of red blood cells facilitate their function?

    • Why is it critical for type 1 pneumocytes to remain healthy?

    • Discuss the adaptations of muscle tissues and their specific roles in body movement.

    • Know adaptations of sperm and egg, lung cells (alveoli), etc.