Biology 3012: Lecture Notes on Cell Biology

Introduction to Cells

• All forms of life are made up of cells.
• Multicellular organisms: Have various cells with different structures and functions working together.
• Single-celled organisms: Are abundant and not visible to the naked eye.

Scale and Measurement

• Logarithmic scale: Illustrates the size difference between millimeters, micrometers, and nanometers.
• Micron: 1,000 times smaller than a millimeter.
• Visibility with the naked eye is limited to larger objects; microscopes are essential for studying smaller forms of life.

Microscopes

• Light microscopes: Use light and lenses to magnify specimens, resolving objects 0.2 micrometers apart.
• Electron microscopes: Provide greater magnification and resolution (0.2 nanometers); include scanning electron microscopes (SEM) for surfaces and transmission electron microscopes (TEM) for internal details.

Cell Theory

• Emerged in the mid-1800s: All living things are composed of cells, and new cells arise from existing cells.
• Cells can be categorized as:
  • Prokaryotic: Smaller, simpler, no nucleus, rigid cell wall.
  • Eukaryotic: Larger, more complex, nucleus, membrane-bound organelles.

Components of Cells

• Similarities: Plasma membrane, cytosol, chromosomes, ribosomes.
• Prokaryotic cells: No nucleus, rigid cell wall, simpler structure.
• Eukaryotic cells: Nucleus, membrane-bound organelles.

Eukaryotic Cell Structures

• Nucleus: Control center, contains DNA, chromatin, and nucleolus (ribosome production).
• Ribosomes: Protein synthesis, found in cytosol or on the rough ER.

Endomembrane System

• Includes nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles.
• Smooth ER: Lipid production, drug detoxification.
• Rough ER: Protein production for transport.
• Golgi apparatus: Modifies, sorts, exports proteins.
• Lysosomes: Digestive enzymes for breaking down molecules.
• Vacuoles: Storage, structural support (large in plants).

Energy Conversion

• Chloroplasts: Photosynthesis in plants, converting sunlight to chemical energy.
• Mitochondria: Cellular respiration in all eukaryotes, converting sugars to ATP.
• Endosymbiotic theory: Chloroplasts and mitochondria were once free-living organisms.

Cytoskeleton

• Provides cell structure, support, movement.
• Flagella and Cilia: Movement; flagella are longer, cilia are shorter and more numerous.
• Dynamic structure, aids in cellular locomotion and internal organization.

Summary

• The lecture covered various cell types, structures, and the functions of cellular components.
• Emphasized the importance of microscopy in understanding cellular biology.
• Discussed energy conversion processes and the endosymbiotic theory.

Study Tips

• Focus on understanding the function of each cell component.
• Remember the difference between prokaryotic and eukaryotic cells.
• Review the process of energy conversion in both chloroplasts and mitochondria.