B1 cells

What is a Cell?

  • Smallest unit of life.

  • Can replicate independently.

  • Basic building block of all living organisms.

Two Main Types of Cells

  1. Prokaryotic Cells

    • Simpler, older type.

    • Lacks a true nucleus.

    • Lacks membrane-bound organelles.

    • Examples: Bacteria, Archaea.

  2. Eukaryotic Cells

    • More complex type.

    • Possess a true nucleus (contains genetic material).

    • Contains various other membrane-bound organelles.

    • Examples: Animal cells, Plant cells, Fungi, Protists.

Key Components of a Cell (General Overview)

  • Cell Membrane (Plasma Membrane)

    • Flexible outer boundary.

    • Controls what enters and leaves the cell.

    • Composed of a phospholipid bilayer with embedded proteins.

  • Cytoplasm

    • All contents within the cell membrane (excluding the nucleus in eukaryotes).

    • Consists of:

      • Cytosol: Jelly-like fluid filling the cell.

      • Organelles: Specialized structures performing specific functions.

  • Genetic Material (DNA/RNA)

    • Contains instructions for building and operating the cell.

    • Eukaryotes: Most DNA in the nucleus.

    • Prokaryotes: Typically a single circular chromosome in the nucleoid.

  • Ribosomes

    • Tiny structures responsible for protein synthesis (making proteins).

    • Found in both prokaryotic and eukaryotic cells.

    • Can be free in the cytoplasm or attached to the endoplasmic reticulum.

Eukaryotic Cell Organelles

  • Nucleus

    • Often the most prominent organelle.

    • Contains the cell's main genetic material (DNA) as chromosomes.

    • Function: Controls cell growth, metabolism, and reproduction.

    • Nuclear Envelope: Double membrane surrounding the nucleus.

    • Nucleolus: Dense structure within the nucleus where ribosomes are assembled.

  • Mitochondria

    • "Powerhouses" of the cell.

    • Function: Cellular respiration (converts glucose into ATP/cellular energy).

  • Endoplasmic Reticulum (ER)

    • Network of membranes.

    • Involved in protein and lipid synthesis.

    • Rough ER:

      • Studded with ribosomes.

      • Synthesizes and modifies proteins for secretion or membrane insertion.

    • Smooth ER:

      • Lacks ribosomes.

      • Involved in lipid synthesis, detoxification, and calcium storage.

  • Golgi Apparatus (Golgi Body/Complex)

    • Function: Modifies, sorts, and packages proteins and lipids from the ER.

    • Packages into vesicles for secretion or delivery to other organelles.

  • Lysosomes (primarily in Animal Cells)

    • Function: Contain digestive enzymes to break down waste materials and cellular debris.

  • Vacuoles (primarily in Plant Cells)

    • Large, membrane-bound sacs.

    • Function: Store water, nutrients, and waste products.

    • In plants, a large central vacuole maintains turgor pressure.

  • Cell Wall (in Plant, Fungi, and Bacteria cells; absent in animal cells)

    • Rigid outer layer (external to the cell membrane).

    • Function: Provides structural support and protection.

  • Chloroplasts (in Plant Cells)

    • Function: Sites of photosynthesis (converts light energy into chemical energy/sugars).