Cell Structure and Function

• Chloroplasts are organelles found in photosynthetic eukaryotic cells.

• They contain chlorophyll, a pigment that absorbs light energy.

• The energy is used to convert CO₂ and H₂O into organic molecules through redox reactions (photosynthesis).

• Structure:

  • Double membrane (outer and inner).

  • Stroma: Thick fluid inside the inner membrane.

  • Thylakoids: Flattened disks containing chlorophyll.

  • Grana: Stacks of thylakoids.

• Mitochondria are responsible for cellular respiration, converting high-energy organic molecules into usable energy (ATP).

• Structure:

  • Double membrane (outer and inner).

  • Cristae: Folds of the inner membrane, increasing surface area for energy production.

  • Matrix: Fluid-filled space inside the inner membrane.

• Both chloroplasts and mitochondria contain DNA, encoding some of their own proteins

The Cell Wall and Cytoskeleton

• Cell Wall:

  • Found in plants, fungi, protists, bacteria, and archaea.

  • Provides structural support and protection.

  • Composed of polysaccharides, glycoproteins, or both.

  • Plants: Made of cellulose and pectins.

  • Fungi: Made of chitin.

• Cytoskeleton:

  • Internal network of protein fibers throughout the cytoplasm.

  • Functions:

    • Provides shape, support, and movement.

    • Anchors the cell membrane and organelles.

    • Allows movement of vesicles and organelles.

    • Helps cells move through their environment (e.g., cilia and flagella).

  • Three types of cytoskeleton fibers:

Cilia and Flagella

• External appendages made of microtubules, covered by cell membrane.

• Flagella:

  • Long, tail-like structures.

  • Move in a whip-like motion.

  • Example: Sperm cells (1 flagellum), Cycad sperm (many flagella).

• Cilia:

  • Short, hair-like structures.

  • Move in a wave-like motion.

  • Example: Paramecium movement, tracheal cells sweep mucus and debris.

Fluorescence Microscopy

• Uses fluorescent dyes to highlight cell structures under UV light.

• Allows observation of cytoskeleton, organelles, proteins, and ions.

• Can be used to track protein and lipid transport.

• Example: Kidney cells stained to show

  • Nuclei (blue)

  • Microtubules (red)

  • Golgi bodies (green)

Fluorescence Microscopy Techniques