Chemical Make Up of Cells

Plasma Membranes

• Encloses the cell.
• Composed of a phospholipid bilayer: two layers of phospholipids.
• Phospholipids have hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.
• Hydrophilic heads face outward towards water; hydrophobic tails face inward, away from water.
• Selectively permeable membrane; regulates what enters and exits the cell via protein channels.

Prokaryotic Basic Cell Structure (Bacteria & Archaea)

• Lack a nucleus and membrane-bound organelles.
• Possess a cell membrane and a cell wall (composition varies between bacteria and archaea).
• Significantly smaller than eukaryotic cells.
• Contain DNA, RNA, proteins, and ions within the cytosol (everything inside the cell membrane).

Eukaryotic Structures (Animals & Plants)

• Share many common features.
• Cytoplasm: The internal environment of the cell membrane.
• Nucleus: Contains DNA; sends instructions for cell function. Surrounded by a nuclear envelope (double membrane).
• Endoplasmic Reticulum (ER): Attached to the nucleus; a primary site for protein and lipid synthesis. Rough ER has ribosomes; smooth ER produces lipids and membrane-bound vesicles for transporting proteins.
• Golgi Apparatus: Processes and packages proteins and lipids; directs their transport within or out of the cell via vesicles.
• Lysosomes: Contain digestive enzymes; can merge with vesicles to break down materials.
• Vacuoles: Larger in plant cells; store water, nutrients, and waste.
• Mitochondria: The "powerhouse" of the cell; generate ATP (energy) through aerobic respiration (using oxygen and sugars). Double-membraned; cristae (inner membrane folds) increase surface area for ATP production.
• Chloroplasts (Plants & some protists): Double-membraned; contain thylakoids (internal membrane stacks) where photosynthesis occurs. Chlorophyll is the pigment capturing light energy to convert carbon dioxide and water into sugars.
• Cytoskeleton: Internal network of fibers and tubules providing structural support and enabling changes in cell shape. Composed of protein filaments and constantly reforming due to non-covalent bonds.

Endosymbiotic Relationship

• Mitochondria and chloroplasts may have originated through an endosymbiotic relationship, where a smaller cell lived inside a larger cell.
• Both contain their own DNA and divide independently within the larger cell.

Explore the essential features of cell structures, including plasma membranes, prokaryotic cells, and eukaryotic cell components. This quiz covers the differences between bacteria, archaea, and eukaryotic cells, providing insights into their unique features and functions. Test your knowledge of the fundamental aspects of cellular biology.