Cell Structure and Function

Cell Structure and Function

• Cells are the basic structural and functional units of all living organisms. They carry out all essential life processes.
• Different cell types have varying structures for specific functions. Nerve cells are specialized for communication, muscle cells for contraction.
• Cells are enclosed by a plasma membrane, controlling substance passage in and out.
• Cells contain internal compartments (organelles) that perform specific tasks, contributing to overall cell function.

Cell Organelles

• Nucleus: The cell's control center, containing DNA organized into chromosomes. Directs protein synthesis and other cellular activities.
• Mitochondria: "Powerhouses" of the cell, generating ATP through cellular respiration. Possess their own DNA and ribosomes, reflecting evolutionary history.
• Golgi apparatus: Modifies, sorts, and packages proteins and lipids for secretion or cellular use. Acts like a cellular post office, processing and transporting products.
• Endoplasmic Reticulum (ER): A membrane network involved in protein and lipid synthesis. Rough ER, studded with ribosomes, synthesizes proteins. Smooth ER synthesizes lipids and detoxifies substances.
• Ribosomes: Sites of protein synthesis. Found free in the cytoplasm or bound to rough ER. Translate mRNA genetic code into polypeptide chains.
• Lysosomes: Contain enzymes that break down waste, damaged organelles, and foreign substances. Cellular recycling centers.
• Vacuoles: Storage sacs for water, nutrients, and waste products. Plant cells often have a large central vacuole maintaining turgor pressure.
• Cytoskeleton: A network of protein filaments (microtubules, microfilaments, intermediate filaments) providing structural support, shape, and enabling cell movement.
• Chloroplasts (plant cells only): Sites of photosynthesis, converting light energy to chemical energy (sugars). Contain chlorophyll, giving plants their green color.
• Cell wall (plant cells only): A rigid outer layer that provides support and protection to plant cells.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic cells: Smaller and simpler, lacking membrane-bound organelles (like mitochondria and nucleus). Examples include bacteria and archaea.
• Eukaryotic cells: Larger and more complex, possessing membrane-bound organelles. Examples include plant and animal cells.
• Structural differences reflect distinct evolutionary origins and adaptations. Eukaryotic compartmentalization allows for efficient specialization and complex biological processes.

Cell Membrane

• The cell membrane is selectively permeable, controlling what enters and exits the cell via various transport mechanisms (passive and active transport).
• The cell membrane is a phospholipid bilayer with embedded proteins and cholesterol, maintaining fluidity without compromising structure.
• This bilayer isolates the cell's internal environment from the external environment,

Cellular Transport

• Passive transport moves substances across the membrane without energy input (e.g., diffusion, osmosis).
• Active transport moves substances against their concentration gradient requiring energy input (e.g., pumps).
• These processes are crucial for maintaining cell homeostasis and enabling essential functions (nutrient uptake, waste removal).