Chapter 3 : Cell Structure and Functions

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Chapter Overview & SLOs

What is the cell? Chapter 3, "Cell Structure and Functions," explores the microscopic building blocks of life. This chapter answers fundamental questions about how cells are organized and how they function. What is the fluid mosaic model of the cell membrane? You will learn the detailed structure of the plasma membrane according to the fluid mosaic model - a bilayer of phospholipids with embedded proteins that can move laterally, creating a fluid structure. The chapter explains how this membrane controls the movement of substances into and out of the cell (selective permeability). What is the role of the cell wall? In plant cells, you will study the cell wall - a rigid outer layer made of cellulose that provides structural support, protection, and prevents bursting in hypotonic solutions. What are the major cell organelles and their functions? You will study the structure and function of essential organelles including: - Nucleus: The control center containing DNA/chromosomes, controlling all cell activities - Mitochondria: The powerhouse of the cell where cellular respiration produces ATP energy - Ribosomes: Sites of protein synthesis (found free in cytoplasm or attached to ER) - Endoplasmic Reticulum (ER): Rough ER (with ribosomes, synthesizes proteins) vs Smooth ER (without ribosomes, synthesizes lipids and detoxifies) - Golgi Apparatus: Modifies, packages, and secretes proteins out of the cell - Lysosomes: Contain digestive enzymes for breaking down waste, old organelles, and pathogens (suicide bags of the cell) - Plastids: Found only in plant cells - include chloroplasts (photosynthesis, contain chlorophyll), chromoplasts (contain colored pigments for fruits/flowers), and leucoplasts (store starch, oils, and proteins) What are the differences between plant and animal cells? The chapter provides a complete comparison including: plant cells have a cell wall (animal cells do not), plant cells have large central vacuoles (animal cells have small temporary vacuoles), plant cells have plastids/chloroplasts (animal cells do not), and animal cells have centrioles (plant cells generally do not). How does structure relate to function in specialized cells? You will learn how cell structure is adapted for specific functions: - Red Blood Cells (RBCs): Biconcave shape increases surface area for oxygen absorption, no nucleus leaves more space for hemoglobin - Neurons (Nerve Cells): Long axons transmit electrical signals over long distances, branched dendrites receive signals from multiple neurons - Muscle Cells: Contain many mitochondria for ATP energy, long and contractile fibers for movement - Mesophyll Cells (Leaf): Contain many chloroplasts for photosynthesis - Epidermal Cells (Skin/Leaves): Flat, tightly packed cells forming a protective barrier These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.

• What is the fluid mosaic model of the cell membrane? Describe the structural model of the cell membrane (fluid mosaic model) including the phospholipid bilayer and embedded proteins, and explain the functions of the cell wall in plant survival including structural support and protection.
• What are the major cell organelles and their functions? Identify major cell organelles including nucleus, mitochondria, ribosomes, Rough ER, Smooth ER, Golgi apparatus, lysosomes, and plastids, and describe their specific biological roles with examples.
• What are the differences between plant and animal cells? Compare the structures of animal and plant cells, emphasizing differences in cell wall, vacuoles, centrioles, and chloroplasts/plastids.
• How does structure relate to function in specialized cells? Explain the relationship between structure and function in specialized cells, including red blood cells (biconcave shape, no nucleus), neurons (long axons, dendrites), muscle cells (many mitochondria, contractile fibers), and mesophyll cells (many chloroplasts).

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