Lecture on Cell Biology

Introduction to Cells

• Cells as the basic unit of life
  • Basic unit of structure and function in organisms
• Structure of cells
  • Membrane separating cytoplasm from the exterior
  • Genetic information in DNA
  • Systems for maintenance and replication
  • Genes transcribed into mRNA, translated by ribosomes into proteins
  • Proteins, including enzymes, are crucial for cell metabolism

Prokaryotic vs Eukaryotic Cells

• Prokaryotic Cells
  • Small, simple, no nucleus, circular chromosomes
  • Contain plasmids, found in Archaea and Bacteria domains
• Eukaryotic Cells
  • Larger, complex, have nucleus, linear chromosomes
  • DNA associated with proteins
  • Presence of mitochondria and membrane-bound organelles

Cell Size and Surface Area

• Relationship between surface area and volume
  • Smaller cells have more surface area relative to volume
  • Larger cells have decreased surface area to volume ratio
• Importance of increased surface area in tissues
  • Facilitates diffusion of molecules/heat
  • Examples: gills of fish, elephant ears, mitochondria, intestinal villi

Compartmentalization in Cells

• Advantages of compartmentalization
  • Allows distinct internal chemistry
  • Provides internal surface area for membrane-bound enzymes
• Compare compartmentalization in prokaryotic and eukaryotic cells
  • Prokaryotic: few compartments, simpler structure
  • Eukaryotic: many compartments, complex internal membranes
• Endomembrane System
  • Dynamic system including nuclear membrane, ER, Golgi apparatus

Origin of Mitochondria and Chloroplasts

• Origin of eukaryotes via endosymbiosis
  • Mutualistic relationship between Archaea and Bacteria
• Evidence for endosymbiosis
  • Mitochondria and chloroplasts have circular DNA, replicate by fission
  • Have own ribosomes similar to bacterial ribosomes

Eukaryotic Cell Parts and Functions

• Nucleus
  • Stores genetic information, has nucleolus for ribosome assembly
• Ribosomes
  • Read mRNA, translate into proteins
  • Found free in cytoplasm or bound to ER
• Mitochondria
  • Convert food energy into ATP, evidence of endosymbiosis
• Endoplasmic Reticulum (ER)
  • Rough ER: protein synthesis
  • Smooth ER: lipid synthesis, detoxification
• Golgi Apparatus
  • Modifies, packages proteins for transport
• Lysosomes
  • Contain hydrolytic enzymes for digestion
• Cytoskeleton
  • Provides structural support, aids in movement
• Chloroplasts (in plants)
  • Photosynthesis, evidence of endosymbiosis

Membrane Structure and Function

• Function of cell membrane as selectively permeable boundary
• Structure of phospholipids
  • Hydrophobic tails, hydrophilic heads
  • Form bilayer in cell membranes
• Fluid mosaic model
  • Membrane composed of phospholipids, proteins, cholesterol

Membrane Transport

• Diffusion
  • Passive transport, molecules move from high to low concentration
  • Simple diffusion for small nonpolar molecules, facilitated for polar
• Active Transport
  • Requires energy, moves molecules against concentration gradient
• Bulk Transport
  • Endocytosis: membrane engulfs substances
  • Exocytosis: vesicles release contents outside cell

Osmosis and Water Potential

• Osmosis
  • Diffusion of water from hypotonic to hypertonic solutions
• Water potential
  • Combines solute potential and pressure potential
• Effects on plant and animal cells
  • Plant cells: turgor pressure from osmotic movement
  • Animal cells: bursting in hypotonic environments

Further Learning

• Emphasized the importance of confident study and understanding
• Resources for further study: quizzes, flashcards, and tutorials
• Engage with additional materials like songs and videos for better understanding