chapter 6 

Overview of Cells

  • Cells vary in complexity; chapter six focuses on fundamental organelles.

  • Understanding organelle functions is essential for grasping cellular processes.

Types of Microscopes

  • Light Microscope:

    • Used for viewing bacteria; cannot see viruses.

    • Requires a 100x magnification objective lens.

  • Electron Microscope:

    • Used for observing structures smaller than bacterial cells (e.g., viruses).

    • Types of Electron Microscopes:

      • Scanning Electron Microscope (SEM):

        • Scans the surface of cells to observe external features.

      • Transmission Electron Microscope (TEM):

        • Allows observation of internal structures within cells.

Shared Characteristics of Cells

  • All Cells Have:

    • Plasma Membrane:

      • Also referred to as cell membrane, cytoplasmic membrane.

    • Cytoplasm:

      • The interior space containing organelles.

    • DNA:

      • Genetic material necessary for cell function.

    • Ribosomes:

      • Responsible for protein synthesis.

Differences Between Cell Types

  • Bacterial Cells:

    • Smaller than eukaryotic cells (about ten times smaller).

    • Includes fimbriae (for attachment) and flagella (for movement).

    • Have a cell wall for protection.

    • Nucleoid vs. Nucleus:

      • Nucleoid:

        • Region containing bacterial DNA, lacks membrane.

      • Nucleus:

        • Enclosed by a nuclear membrane in eukaryotic cells containing DNA.

Eukaryotic Versus Prokaryotic Cells

  • Eukaryotic Cells:

    • Have a nucleus with a double membrane surrounding DNA.

  • Prokaryotic Cells:

    • Have a nucleoid; DNA is not membrane-bound.

Plant Cells Versus Animal Cells

  • Plant Cells:

    • Have a cell wall (protection), chloroplasts (photosynthesis), and central vacuoles (storage).

  • Animal Cells:

    • Lack cell walls, have centrioles (cell division), and lysosomes (digestion).

Additional Cell Structures

  • Centrosome: Location of centrioles in animal cells.

  • Lysosomes:

    • More commonly associated with animal cells; functions in digestion.

Functionality of Cells

  • Cells cannot increase in size indefinitely due to diffusion limitations.

  • Surface Area to Volume Ratio:

    • Importance of maintaining a high surface area to volume ratio for efficient nutrient exchange.

    • Larger cells face challenges in obtaining nutrients and disposing of waste effectively.

Cell Membrane Structure

  • Composed of a phospholipid bilayer; exhibits selective permeability.

  • Collaborates with proteins to control substance movement into and out of the cell.

Chromatin and Chromosomes

  • Chromatin:

    • Composed of DNA wrapped around histones, facilitates organization of genetic material.

  • Chromosomes:

    • Formed from tightly packed chromatin during cell division, containing genetic information.

Nucleus and Nucleolus

  • Nucleus:

    • Double membrane structure housing genetic material.

    • Nuclear pores regulate substance movement.

  • Nucleolus:

    • Dense area within the nucleus; site of ribosomal RNA synthesis and ribosome assembly.

Conclusion

  • Understanding cell structure and function is foundational to grasping biological processes, including protein synthesis and cellular organization.