Eman 4

• Organisms were perceived as being complete and inseparable into smaller parts


  Prior to the 1600s, people did not have the ability to see smaller structures due to lack of microscopes
• Anton van Leeuwenhoek was the first to view a living cell under a microscope


  1675
• Cell theory

  • All living organisms are composed of cells
  • The cell is the basic functional unit of life
  • Cells arise only from pre-existing cells
  • Cells carry genetic information in the form of DNA
  • Genetic material is passed on from parent to daughter cell
  • Energy flow occurs within cells
• Viruses are small structures that contain genetic material but do not reproduce on their own, so they are not considered living organisms
• Prokaryotic cells


  Unicellular organisms without a true nucleus enclosed in a membrane
• Eukaryotic cells


  Cells with a true nucleus enclosed in a membrane, can be unicellular or multicellular
• Similarities between prokaryotic and eukaryotic cells

  • Cell membranes
  • Ribosomes
• Differences between prokaryotic and eukaryotic cells

  • Prokaryotes have naked, circular DNA, eukaryotes have DNA bound to proteins and linear
  • Prokaryotes reproduce by binary fission, eukaryotes use mitosis and meiosis
• Eukaryotic cells


  • Contain membrane-bound organelles
  • Have a true nucleus enclosed in a membrane
• Cell membrane

  Phospholipid bilayer with hydrophilic exterior and hydrophobic interior to control what enters and exits the cell
• Nucleus


  Contains DNA organized into chromosomes, surrounded by a nuclear membrane with pores to allow exchange of materials
• Nucleolus


  Part of the nucleus where ribosomal RNA is synthesized
• Mitochondria


  Has an inner and outer membrane, the "powerhouse" of the cell where ATP is produced and cellular respiration occurs
• Lysosomes


  Contain hydrolytic enzymes that break down substances and recycle worn-out organelles
• Peroxisomes


  Break down fatty acids and amino acids, and detoxify poisons
• Endoplasmic reticulum (ER)


  Rough ER has ribosomes for translation of proteins destined for secretion, smooth ER is used for lipid synthesis and detoxification
• Golgi apparatus


  Modifies, packages, and directs cellular products to specific locations, like the "post office" of the cell
• Cytoskeleton


  Provides stability and rigidity to the cell structure, includes microtubules, microfilaments, and intermediate filaments
• Golgi apparatus


  Stacked membrane-bound sacs in which cellular products are modified, packaged, and directed to specific cellular locations
• Cytoskeleton


  • Provides stability and rigidity to the overall structure of the cell
  • Provides transport pathways for molecules
  • Provides structural protection for the cell
• Components of the cytoskeleton

  • Microtubules
  • Microfilaments
  • Intermediate filaments
• Ribosomes


  Known for their function in protein synthesis
• Both eukaryotic cells and prokaryotic cells have ribosomes
• The cytoskeleton provides stability and rigidity to the overall cell structure and helps maintain its shape
• Microfilaments


  • Composed of actin
  • Provide structural protection for the cell
  • Cause muscle contractions through interactions with myosin
  • Help with cleavage furrow during cytokinesis
• Microtubules


  • Composed of tubulin
  • Create pathways for motor proteins
  • Contribute to the structure of cilia and flagella
• Microtubules are organized into 9 pairs of microtubules in a ring with 2 microtubules at the center (9+2 structure)
• Intermediate filaments

  • Involved in cell-to-cell adhesion
  • Help maintain the integrity of the cytoskeleton
  • Can anchor organelles
  • Example: Keratin
• One of the unique characteristics of eukaryotic cells is the formation of tissue with division of labor
• Types of tissue

  • Epithelial
  • Connective
  • Muscle
  • Nervous
• Epithelial tissue


  • Covers the body and lines its cavities, providing protection against pathogens and desiccation
  • Involved in absorption, secretion, and sensation in certain organs
  • Tightly joined to each other and can form an underlying layer for connective tissue (basement membrane)
• Connective tissue


  • Supports the body and provides a framework for epithelial cells
  • Forms the stroma or support structure by secreting materials to form an extracellular matrix
  • Examples: bone, cartilage, ligaments, adipose tissue, blood
• Prokaryotes are the simplest of all organisms and include all bacteria
• Prokaryotes do not contain any membrane-bound organelles, and their genetic material is organized into a single circular molecule of DNA in the nucleoid region
• Domains of life

  • Archaea
  • Bacteria
  • Eukarya
• Archaea


  Usually extremophiles that live in harsh environments
• Bacteria


  Have many similar structures to eukaryotes and have complex relationships with humans (can help or harm)
• Bacterial shapes

  • Spherical (cocci)
  • Rod-shaped (bacilli)
  • Spiral (spirilli)
• Bacterial metabolic processes

  • Aerobic
  • Anaerobic
• Aerobic bacteria


  • Require oxygen for growth
  • Obligate aerobic: cannot survive without oxygen
  • Microaerophilic: require lower concentrations of oxygen