Introduction to Cell Biology

1. Types of Cells
   1. Prokaryotic Cells
      1. Characteristics
         1. Lack of nucleus and membrane-bound organelles
         2. Simple, single-celled organisms
         3. Generally smaller than eukaryotic cells
         4. DNA is circular and located in a nucleoid region
         5. Cell division by binary fission
         6. Cell walls primarily composed of peptidoglycan (bacteria)
      2. Cell Structures
         1. Plasma membrane with potential invaginations
         2. Cell wall (bacteria: peptidoglycan; archaea: protein or other compositions)
         3. Ribosomes (70S type, different from eukaryotic ribosomes)
         4. Flagella for mobility in some species
         5. Pili for attachment or DNA transfer (bacterial conjugation)
      3. Examples
         1. Bacteria
            1. Pathogenic (e.g., Escherichia coli, Streptococcus)
            2. Non-pathogenic (e.g., Lactobacillus, Rhizobium)
            3. Cyanobacteria (photosynthetic bacteria)
         2. Archaea
            1. Extremophiles (e.g., Halophiles, Thermophiles)
            2. Methanogens (producers of methane gas)
   2. Eukaryotic Cells
      1. Characteristics
         1. Presence of a true nucleus enclosed by a nuclear membrane
         2. Complex internal structure with membrane-bound organelles
         3. Linear DNA organized into chromosomes
         4. Larger than prokaryotic cells
         5. Undergo mitosis and meiosis for cell division
      2. Organelles
         1. Nucleus
            1. Stores genetic material (DNA)
            2. Site of transcription
            3. Nuclear pores regulate transport
         2. Mitochondria
            1. Cellular powerhouse; site of ATP synthesis
            2. Contains own DNA; semi-autonomous
         3. Endoplasmic Reticulum
            1. Rough ER: studded with ribosomes, protein synthesis
            2. Smooth ER: lipid synthesis, detoxification, calcium storage
         4. Golgi Apparatus
            1. Modifies, sorts, and packages proteins and lipids
            2. Vesicle formation for transport
         5. Lysosomes
            1. Digestive enzymes for breakdown of macromolecules
            2. Catabolize waste materials and cellular debris
         6. Peroxisomes
            1. Break down fatty acids and toxic peroxides
            2. Role in detoxification
         7. Chloroplasts (in plant cells)
            1. Photosynthesis: conversion of light energy to chemical energy
            2. Contains chlorophyll and other pigments
            3. Also carries its own DNA
         8. Animal Cells
            1. Unique structures: centrioles, lysosomes
            2. Undergo cytokinesis via cleavage furrow
         9. Plant Cells
            1. Unique structures: cell wall (cellulose), chloroplasts, large central vacuole
            2. Undergo cytokinesis via cell plate formation
         10. Fungal Cells
             1. Cell wall composed of chitin
             2. May be unicellular (yeasts) or multicellular (molds)
         11. Protist Cells
             1. Highly diverse group; may be plant-like, fungi-like, or animal-like
             2. Often unicellular, can be colonial or multicellular
      3. Examples
         1. Animal cells
            1. Specialized types: nerve cells, muscle cells, blood cells
            2. Various functions dependent on structure
         2. Plant cells
            1. Guard cells, root cells, leaf cells
            2. Engaged in photosynthesis, respiration, and other processes
         3. Fungal cells
            1. Yeast cells involved in fermentation
            2. Mycelium structure in mold
         4. Protist cells
            1. Amoebas utilizing pseudopodia for movement
            2. Algae conducting photosynthesis
            3. Paramecia using cilia for locomotion and feeding