Science and cells

• Science is an iterative process
• the scientific process provides a framework for asking questions about what we see and devising a way to answer them in an organized , systematic, and unbiased way
• a hypothesis attempts to explain your observations by proposing a relationship or connections between two or more variables
• Hypotheses allow you to make testable predictions
• Predictions: if hypothesis is supported, what would you expect to see
• Theory: a general explanation of the world supported by many experiments and observations
• Abiogenesis: life arises spontaneously from non-living matter
• Biogenesis: life comes only from other life
• the cell theory has two basic parts:

  • All living things (organisms) are made of one or more cells
  • All cells arise from other cells
• Prokaryotic cells

  • Single-celled organisms (with exceptions)
  • Live in all kinds of environments
  • Cell structure is relatively simple but capable of complex chemistry
• Prokaryotic Cells

  • DNA and RNA
  • Nucleoid
  • Ribosomes
  • Cell membrane
  • Cell wall
  • cytoplasm
• Prokaryotic Cells

  Don't have:

  • A membrane-bound nucleus
  • energy-producing organelles
  • a sex
• Prokaryotic DNA is present as a single circular chromosome
• Most prokaryotes (particularly bacteria) can also carry additional DNA in the form of plasmids
• Prokaryotic shapes and sizes

  • Tiny
  • Bacterial cells are 200nm-2um
  • Small size allows them to obtain nutrients by diffusion
  • Don't need to be as complex as eukaryotes
• Eukaryotic cells

  • Different structures for different environments and functions
• Eukaryotic cells

  • Membrane bound organelles
  • complex chemistry occurs in inside and outside of organelles
• Eukaryotic cells

  • Cytoskeleton
  • Much bigger and complex than prokaryotic cells
• Viruses: The cellular undead

  • Similar to living organisms:
  • they have the ability to store and transmit information
• Viruses: The cellular undead

  • dissimilar to living organisms:
  • they don't have the ability to harness energy from the environment
• Viruses: The cellular undead

  • dissimilar to living organisms:
  • Cells can break down chemical compounds, releasing energy and converting it into a usable from (ATP), viruses cannot
• Viruses: The cellular undead

  • dissimilar to living organisms:
  • They require cells as hosts to read and use the information contained in their genetic material
• Viruses: The cellular undead

  • dissimilar to living organisms:
  • they require cells as hosts to replicate