Biochemistry

• The levels of organization in the human body start with the atom, then molecules, macromolecules, organelles, 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, originate from existing cells, transduce energy to maintain life processes, have a selective barrier (plasma membrane), utilize genetic information, and contain catalysts (enzymes) which speed up chemical reactions
• Metabolism involves catabolism where complex molecules are broken down into simpler ones, releasing energy, usually by oxidation or hydrolysis, and generating ATP and/or reducing equivalents
• The Central Dogma of Molecular Biology explains how genetic information flows from DNA to RNA to protein
• Cells are classified as prokaryotic (lack a membrane-bound nucleus and organelles) or eukaryotic (possess a membrane-bound nucleus and 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 surrounded by a cell wall made of peptidoglycan, a heteropolymer of substituted glucose, cross-linked to a short tetrapeptide containing a D-amino acid
• Prokaryotic cells have a single circular DNA molecule, smaller ribosomes (70S), and usually have a cell wall
• Prokaryotic cells lack a nucleus, have a diameter of 1-10 mm, a cytoskeleton, and no cytoplasmic organelles
• Eukaryotic cells contain membrane-bounded organelles, a membrane-bounded nucleus, and a system of internal membranes
• Biological membranes are primarily composed of lipids and proteins, with a lipid bilayer and various types of proteins and lipids responsible for their functions
• The plasma membrane is a selective barrier that regulates the cell's internal composition, separates the external and internal environment, and contains carbohydrates associated with lipids or proteins
• Membrane proteins have functions like transport, enzymatic activity, receptors, cell-cell recognition, adhesion, and attachment to the cytoskeleton
• Cell walls are extracellular matrices found in plants, fungi, many protists, and bacteria, external to and surrounding the plasma membrane
• Levels of organization in the human body:

  • Atom (basic unit of matter)
  • Molecules (basic units of life)
  • Macromolecules (essential for life)
  • Organelles (basic units of cells)
  • Tissues (groups of cells with a specific function)
  • Organs (larger structures with a specific function)
  • Organ systems (groups of organs working together)
  • Organism (highest level of organization in the human 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:

  • Genetic information flows from DNA to RNA to protein
  • DNA is transcribed into RNA, which is then translated into protein

  
• Six kingdoms of living things:

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

  
• Structure of a prokaryotic cell:

  • Contains a cell wall composed of peptidoglycan
  • Has a bacterial cytoskeleton
  • Includes non-membranous organelles like ribosomes and proteasomes

  
• Structure of the bacterial cell wall:

  • Composed of peptidoglycan
  • Peptidoglycan chains cross-linked by pentaglycine bridges
  • Lysozyme cleaves the β1→4 linkages between N-acetylglucosamine and N-acetylmuramic acid residues

  
• Diagram of a cell:

  • Divided into protoplasm, plasma membrane, and nucleus
  • Protoplasm includes cytoplasm and cellular inclusions
  • Plasma membrane separates the cell from its environment
  • Nucleus contains DNA and controls the cell's activities