AP Biology · Summary

Unit 2 summary

  1. Proteins for export are made on the rough ER, sorted in the Golgi complex and released by vesicles; ribosomes are in every cell, membrane-bound organelles only in eukaryotes.
  2. For a cube, surface-area-to-volume ratio is 6 divided by the side length; smaller cells have larger ratios and exchange materials faster for their volume.
  3. The bilayer's nonpolar middle lets small nonpolar molecules through and holds back ions and large polar molecules, which need proteins.
  4. Passive transport moves substances down their gradient with no cell energy; active transport moves them against it using a pump powered by ATP; cotransport uses one gradient to drive another substance.
  5. Water potential = pressure potential + solute potential; pure water is 0, solutes make it negative, and water moves from higher to lower water potential.
  6. Solute potential = -iCRT, with R = 0.0831 liter-bar per mole-kelvin and T in kelvin.
  7. Mitochondria and chloroplasts have two membranes, their own circular DNA and bacteria-like ribosomes, and divide on their own: evidence for endosymbiosis.