Biol 103 w1

• Mitochondrion

  • Aerobic, allowed its anaerobic host to survive in previously uninhabitable, oxygen-rich environments
  • Consumes oxygen to efficiently extract energy from carbon sources like glucose, producing carbon dioxide and water in the process
• Host cell with Mitochondrion

  More efficient, grew, became a predator, engulfed a cyanobacterium
• Chloroplast

  • Consumes water and carbon dioxide as it captures energy from light and funnels it into the chemical energy of glucose, releasing oxygen in the process
• DNA in organelles is not similar to nucleic DNA
• Mitochondrial DNA is a circular strand, as in prokaryotes
• Mitochondria and plastids multiply by division – like prokaryotes
• Mitochondria and plastids cannot be made by cell cytoplasm
• Mitochondria and plastids have independent reproductive mechanism
• If a cell loses these organelles, it cannot make more
• Plastids & Mitochondria make proteins by similar pathways to prokaryotes – differ from mechanism in eukaryote cells
• Mitochondria use O2 and produce ATP in similar ways to purple-aerobic bacteria
• Chloroplasts are similar to photosynthetic bacteria in having similar chlorophyll
• Mitochondria and plastids are susceptible to tetracycline and streptomycin that affect prokaryotes, but the cytoplasm of eukaryotes is not affected by these antibiotics
• Mitochondria and plastids are about the same size as prokaryotes – 1-10 um
• Paulinella chromatophora is an example of a single-celled organism that has incorporated a photosynthetic endosymbiont
• Multicellularity


  • Probably preceded by sexual reproduction
  • Evolved independently for plants, animals, slime molds, others
  • Single celled flagellate became colonial
  • Syncytial theory
  • Incomplete division

  
• Why multicellularity?


  • Larger size & internal environment gave better protection
  • Division of labour
  • Life span
• Multicellularity arose, but remained small (mostly algae) until 700 - 565 million years ago


  1.5 and 1.2 billion years ago
• Ediacaran fossils

  
• Cambrian Explosion
• Three theories for Cambrian Explosion

  • Skeletons (support, muscle attachment, burrowing)
  • Predation (ecology, prevented dominance, adaptation)
  • Oxygen levels (transport through thick skins / shells)
• Earth's origin


  4.5 billion years ago
• Prokaryotes dominate


  3.5 billion years ago
• Oxygen accumulates


  2.5 billion years ago
• Eukaryotes evolve


  2.1-2.7 billion years ago

  
• Multicellularity (small)


  1.5 – 2 billion years ago
• Ediacaran fossils / Cambrian explosion

  0.5 billion years ago

  
• Humans


  0.5 billion years ago
• Messenger RNA (mRNA)


  Transcribed from DNA
• Transcription


  Any RNA in which DNA is the template
• Translation


  Synthesis of a polypeptide directed by mRNA, occurring at ribosomes
• Genes to proteins


  • DNA
  • RNA
  • Proteins
  • Transcription
  • Translation

  
• At any given moment there are thousands of reactions occurring in a living cell
• Cellular respiration extracts energy from stored sources to fuel these processes
• All these reactions have to be strictly controlled and regulated
• Cells must also respond to subtle changes and co-ordinate accordingly
• Metabolism


  Describes the energy flow in a cell
• Catabolic reactions


  Break down larger molecules to release energy
• Anabolic reactions


  Build up larger molecules using energy
• Metabolism


  1. Starting molecule

  2. Reaction 1

  3. Reaction 2

  4. End product