Biol 261

1. Nucleus • Function: Acts as the control center of the cell, containing the cell’s genetic material (DNA). It controls gene expression and cell activities like growth, metabolism, and reproduction. • Structure: It’s surrounded by a double membrane called the nuclear envelope, which has pores to allow the movement of molecules in and out. 2. Mitochondria • Function: Known as the powerhouse of the cell, mitochondria generate ATP (adenosine triphosphate), the energy currency of the cell, through cellular respiration. • Structure: Mitochondria have a double membrane. The inner membrane is folded into structures called cristae, which increases surface area for energy production. 3. Endoplasmic Reticulum (ER) • Rough ER: • Function: Involved in protein synthesis and has ribosomes attached to its surface. • Structure: It looks rough due to the ribosomes on its surface. • Smooth ER: • Function: Synthesizes lipids and detoxifies certain chemicals. It also stores calcium ions. • Structure: Lacks ribosomes, making it smooth in appearance. 4. Golgi Apparatus (Golgi Body) • Function: Responsible for modifying, sorting, and packaging proteins and lipids from the ER for delivery to different destinations within or outside the cell. • Structure: A series of stacked membranes that resemble a stack of pancakes. 5. Lysosomes • Function: Contain digestive enzymes that break down waste materials, cellular debris, and foreign invaders (like bacteria). • Structure: Small, membrane-bound sacs that contain acidic enzymes. 6. Ribosomes • Function: The sites of protein synthesis. They translate messenger RNA (mRNA) into proteins. • Structure: Composed of two subunits (large and small), and can be found either floating freely in the cytoplasm or attached to the rough ER. 7. Cytoskeleton • Function: Provides structural support, helps with cell movement, and aids in intracellular transport. It also plays a role in cell division. • Structure: Made up of microtubules, intermediate filaments, and actin filaments. 8. Chloroplasts (in plant cells) • Function: Responsible for photosynthesis, converting light energy into chemical energy stored in glucose. • Structure: Contain the pigment chlorophyll, which captures light energy. They have a double membrane and internal structures called thylakoids, which are stacked into grana. 9. Vacuoles • Function: Storage organelles that store nutrients, waste products, and help maintain cell turgor pressure (the pressure of the cell contents against the cell wall). • Structure: Large in plant cells (central vacuole), smaller in animal cells. 10. Plasma Membrane • Function: Acts as a barrier, controlling what enters and leaves the cell. It maintains the cell’s internal environment. • Structure: A phospholipid bilayer with embedded proteins, cholesterol, and