Cell Structures and Functions - In Depth Notes

Cytoskeleton

• The cytoskeleton supports organelles and cell shape and plays a critical role in cell motion.

• Main components include:

  • Microtubule:
  • A tube of protein molecules found in the cytoplasm, centrioles, cilia, and flagella.
  • Intermediate Filament:
  • Intertwined protein fibers that provide support and strength to the cell.
  • Actin Filament:
  • Twisted protein fibers responsible for cell movement.

• Centrioles:

  • A complex assembly of microtubules that occurs in pairs.

Endoplasmic Reticulum (ER)

• Smooth Endoplasmic Reticulum:

  • A system of internal membranes that aids in the manufacture of carbohydrates and lipids.

• Rough Endoplasmic Reticulum (RER):

  • Internal membranes studded with ribosomes that carry out protein synthesis.

Nucleus

• Functions as the command center of the cell.

• Contains the Nucleolus, which is the site of ribosome production.

• Nuclear Envelope:

  • A double membrane that separates the nucleus from the cytoplasm.

• Nuclear Pore:

  • Openings embedded with proteins to regulate passage into and out of the nucleus.

Ribosomes

• Small complexes of RNA and protein that serve as the sites for protein synthesis.

Peroxisomes

• Membranous vesicles containing enzymes that detoxify potentially harmful molecules.

Cytoplasm

• A semifluid matrix containing the nucleus and other organelles.

Mitochondria

• Organelles where energy is extracted from food during oxidative metabolism.
• Play a critical role in Cellular Respiration and produce ATP, the energy molecule for cells.
• Mitochondria have a double membrane, and the inner membrane is folded to increase surface area for enzyme activity.

Lysosomes

• Vesicles that contain hydrolytic enzymes necessary for breaking down macromolecules and recycling worn-out cellular components.
• The term “lysosome” comes from the Greek word "lyse" meaning break/dissolve and "some" meaning body/structure.

Golgi Apparatus

• Composed of about a dozen large flattened sacs, functioning like a shipping and receiving warehouse.
  • Vesicles from Smooth and Rough ER deposit proteins into the Golgi Apparatus where they are modified, sorted, and repackaged for transport.
  • Proteins are sent to various parts of the cell or packaged into secretory vesicles to be released outside the cell.

Chloroplasts

• Found in plants, their primary function is to perform photosynthesis.

Cellular Respiration

• A process utilizing oxygen and glucose to produce ATP, carbon dioxide, and water.
• High-energy cells like muscle and sperm cells have many mitochondria to support this process.

Cytoskeleton Structure

• A network of microscopic filaments and tubules providing cell structure and support.
• The cytoskeleton is involved in structure anchoring and movement of organelles.

Microfilaments

• Actin filaments, with a braided appearance, are one type of microfilament.

Microtubules

• Larger structures compared to microfilaments, aiding in the construction of larger components of the cytoskeleton.

Centrioles and Larger Structures

• Centrioles are formed from 27 microtubules in a “9 + 0” arrangement.
• Other structures include basal bodies, cilia, and flagella, all made from microtubules.
  • Cilia: Shorter and whip-like, they move substances across cell surfaces.
  • Flagella: Longer, whip-like structures (e.g., sperm cells) for locomotion, with a “9 + 2” arrangement (9 doublets with 2 central microtubules).