2.1 Cell Structure and Function

Explain how the structure and function of subcellular components and organelles contribute to the function of cells.

• Ribosomes are comprised of ribosomal RNA (rRNA) and protein. These non-membrane, subcellular structures are found in cells in all forms of life and reflect the common ancestry in all known life. Ribosomes synthesize proteins according to messenger RNA (mRNA) sequences.
• The endomembrane system consists of a group of membrane-bound organelles and subcellular components (endoplasmic reticulum (ER), Golgi complex, lysosomes, vacuoles and transport vesicles, the nuclear envelope, and the plasma membrane) that work together to modify, package, and transport polysaccharides, lipids, and proteins intercellularly.
• Endoplasmic reticulum provides mechanical support by helping cells maintain shape and plays a role in intracellular transport.
  • i. Rough ER is associated with membrane-bound ribosomes, allows for the compartmentalization of cells, and helps carry out protein synthesis.
  • ii. Smooth ER functions include the detoxification of cells and lipid synthesis.
  • Exclusion: Knowledge of the specific functions of smooth ER in specialized cells is beyond the scope of the AP Exam.
• The Golgi complex is a membrane-bound structure that consists of a series of flattened membrane sacs. Functions of the Golgi include:
  • i. Correctly folding and chemically modifying newly synthesized cellular products
  • ii. Packaging proteins for trafficking
  • Exclusion: Knowledge of the role of Golgi in the synthesis of specific phospholipids and packaging of specific enzymes for lysosomes, peroxisomes, and secretory vesicles is beyond the scope of the AP Exam.
• Mitochondria have a double membrane that provides compartments for different metabolic reactions involved in aerobic cellular respiration. The outer membrane is smooth, while the inner membrane is highly convoluted, forming folds that enable ATP to be synthesized more efficiently.
• Lysosomes are membrane-enclosed sacs that contain hydrolytic enzymes that digest material. Lysosomes also play a role in programmed cell death (apoptosis).
• Vacuoles are membrane-bound sacs that play many different roles.
  • i. In plant cells, a specialized large vacuole maintains turgor pressure through nutrient and water storage.
  • ii. In animal cells, vacuoles are smaller in size, are more plentiful than in plant cells, and store cellular materials.
• Chloroplasts are specialized organelles that are found in plants and photosynthetic algae. Chloroplasts contain a double membrane and serve as the location for photosynthesis.