Specialised Cells Notes

Cell Specialisation

  • Success Criteria: By the end of the session, students should be able to:

    • Discuss adaptations of specialized cells.

    • Demonstrate in-depth understanding of:

    • Similarities and differences in cell shapes.

    • Sizes of cells.

    • Relative number of organelles and internal structures in plant and animal cells.

    • Relation of cell variations to the overall functioning of the organism.

Cell Differentiation

  • Definition: Cell differentiation refers to the process by which not all cells in an organism exhibit the same shape or the same number of organelles.

  • Dependence on Function: The specific shape and organelle count in a cell is highly dependent on the function that the cell performs.

Specialized Cells

  • Significance: Specialized cells are adapted for particular functions within an organism. Examples include various cell types which have unique features to facilitate their roles.

Designing a Cell

  • Activity: Design a cell. All designed cells must fulfill certain functions based on their descriptions.

    • Example 1:

    • Cell Type: Animal cell

    • Functions:

      • Move around.

      • Carry a significant amount of information in the nucleus.

      • Have the ability to burrow through walls.

    • Example 2:

    • Cell Type: Animal cell

    • Functions:

      • Protect itself.

      • Store significant amounts of energy.

      • Carry a significant amount of information in the nucleus.

    • Example 3:

    • Cell Type: Animal cell

    • Functions:

      • Move around.

      • Sweep bits of dust and mucus from airways.

      • Found specifically in the throat.

Different Types of Cells

  • In multicellular organisms, various types of cells exist, tailored for specific functions. Examples include:

    • Red Blood Cell

    • Cheek Cell

    • Nerve Cell

    • Muscle Cell

    • Epithelial Cell

    • Sperm Cell

    • Egg Cell

Cell Size

  • General Observation:

    • Plant cells tend to be larger than animal cells.

  • Plant Cell Structures:

    • Typically possess a large central vacuole which is crucial for storage and maintaining the plant's structural integrity.

  • Animal Cell Structures:

    • Vacuoles in animals are generally smaller in size and often present in greater numbers.

Cell Shape

  • Variation in Shape:

    • Cellular shapes can vary significantly, especially in animal cells, to optimize their respective functions.

    • Nerve Cells:

    • Long and thin shape minimizes disruption to nerve impulses.

    • The nucleus is positioned away to avoid interfering with nerve message transmission.

    • Root Hair Cells:

    • Exhibit a large surface area to enhance water uptake from the soil.

    • Intestinal Cells:

    • Feature villi (membrane projections) which increase surface area to maximize the absorption of digested food into the bloodstream.

Cellular Structures with Specialized Functions

  • Ciliated Epithelial Cells:

    • Form the lining of the trachea and are responsible for moving dust and dirt trapped in mucus out of the airways, protecting delicate structures like alveoli.

    • Possess an extensive Golgi apparatus to produce vesicles containing mucus.

Relative Number of Organelles

  • The quantity and positioning of organelles within a cell are intrinsically linked to the cell’s function.

Organelles Overview

  • Ribosomes:

    • Typically found in large numbers in secretory cells.

    • Function: Produce proteins and enzymes (e.g., enzymes produced in salivary glands).

  • Rough Endoplasmic Reticulum (Rough ER):

    • Predominantly found in secretory cells (e.g., digestive cells, white blood cells, endocrine cells).

    • Example:

      • Pancreatic cells synthesize and secrete enzymes; white blood cells synthesize and secrete antibodies; endocrine glands synthesize hormones.

  • Smooth Endoplasmic Reticulum (Smooth ER):

    • Associated with lipid production; cells producing steroids have extensive amounts of smooth ER.

    • Example: Ovary cells produce and secrete hormones like estrogen and progesterone, thus have a large amount of smooth ER.

  • Lysosomes:

    • Specialised vacuoles containing enzymes.

    • Formed from vesicles produced by the Golgi body.

    • Common in sperm cells, where they release enzymes to penetrate the ova's plasma membrane and cytoplasm for fertilization.

    • Also found in:

      • Liver cells

      • White blood cells

  • Chloroplasts:

    • Exclusively found in plant cells exposed to light (e.g., palisade cells beneath the upper epidermis of leaves).

  • Mitochondria:

    • Present in all eukaryotic cells that undergo aerobic respiration.

    • High numbers are found in cells requiring significant energy.

    • Examples of Cells with High Mitochondrial Content:

      • Skeletal muscle cells (energy for muscle contraction).

      • Sperm cells (energy for movement towards egg).

      • Liver cells (energy for numerous chemical reactions in metabolism).

Comparison of Mitochondria in Animal and Plant Cells

  • More Mitochondria in Animals:

    • Generally, animal cells possess more mitochondria than plant cells due to:

    • Warm-blooded animals requiring more energy for maintaining body heat.

    • Higher energy expenditure due to frequent movement compared to plants, which do not require additional energy for heat maintenance.

Summary of Key Concepts

  • Overall Understanding: Not all cells have identical shapes or the same number of organelles. The shape and organelle count is tailored to the specific needs and functions of the cell within an organism, highlighting the intricate relationship between structure and function in biological systems.