Cellular organization

• The levels of organization in the human body start with the atom, then molecules, cells, tissues, organs, organ systems, and finally the organism

  
• Living systems possess the ability to reproduce, metabolism, mutagenicity, replicate and express genetic information
• Living organisms are composed of molecules assembled from atoms like C, H, O, N, P & S
• Cells are the unit of structure and function, originating from existing cells, transducing energy to maintain life processes, having a selective barrier (plasma membrane) containing protoplasm, utilizing genetic information to guide the synthesis of most cell components, and containing catalysts (enzymes) which speed up chemical reactions
• Metabolism involves catabolism where complex molecules are broken down into simpler ones, releasing energy, generating ATP and/or reducing equivalents
• The Central Dogma of Molecular Biology explains how genetic information is utilized to synthesize RNA and proteins, necessary for life processes
• Cells are classified into prokaryotic and eukaryotic cells based on the presence or absence of a membrane-bound nucleus and membrane-bounded organelles
• Prokaryotic cells lack a complex system of interconnected internal membranes found in eukaryotes, exist in various shapes like spherical, rodlike, or helically coiled, and have no membranous organelles
• Prokaryotic cells have a plasma membrane usually infolded to form mesosomes, a single circular DNA molecule condensed to form the nucleoid, and a cell wall made of peptidoglycan
• Prokaryotic cells are the most abundant organisms, lack a complex system of interconnected internal membranes found in eukaryotes, and have no membranous organelles
• Prokaryotic cells have a cytoskeleton that maintains cell shape, internal organization, provides mechanical support, plays a role in cell division, and establishes cell polarity
• Eukaryotic cells contain membrane-bounded organelles, a membrane-bounded nucleus & system of internal membranes, and can be unicellular (Protists) or multicellular (fungi, plants, animals)
• Biological membranes are primarily composed of lipids & proteins, with a lipid bilayer made of phospholipids and various types and ratios of proteins and lipids responsible for their varying functions
• The plasma membrane is a selective barrier that regulates the cell's internal composition, surrounds and delimits the cell, separates external & internal environments, and contains carbohydrates associated with lipids or proteins
• Membrane proteins have functions like transport, enzymatic activity, receptors, cell-cell recognition, cell-cell adhesion, and attachment to the cytoskeleton
• Cell walls are an extracellular matrix found in plants, fungi, many protists, and bacteria, containing cellulose in plants and chitin in fungi
• Levels of organization in the human body:

  • Atom (basic unit of matter)
  • Molecules (building blocks of cells)
  • Cells (basic units of tissues)
  • Tissues (form organs)
  • Organs (form organ systems)
  • Organ systems (major functional units)
  • Organism (complete living body)

  
• Six essential characteristics of life:

  1. Compartmentalization

  2. Adaptability

  3. Energy transduction

  4. Information processing

  5. Growth and division

  6. Mobility

  
• Central dogma of molecular biology:

  • DNA transcribed into RNA
  • RNA translated into protein
  • DNA replication (copying of DNA)

  
• Six kingdoms of living things:

  • Archaebacteria
  • Eubacteria
  • Protista
  • Fungi
  • Plantae
  • Animalia

  
• Phylogenetic tree titled "Tree of Life":

  • Organisms divided into three domains: Bacteria, Archaea, Eukarya
  • Bacteria domain includes prokaryotic organisms
  • Archaea domain includes prokaryotic organisms related to eukaryotes
  • Eukarya domain includes eukaryotic organisms

  
• Structure of the bacterial cell wall:

  • Composed of peptidoglycan
  • Protects bacterium from osmotic lysis

  
• Overview of cellular structures:

  • Membrane-bound organelles
  • Non-membranous organelles
  • Cellular inclusions