 Atoms  Elements  Compounds  In Biological Compounds…often form covalent bonds  Proportions in Living Organisms  C 19%  H 10%  O 65%  N 3%

 SULFUR › In some amino acids (disulfide bridges) › Proteins › Chemoautotrophs use it as energy source

 CALCIUM › Cell structure, movement  Cell walls, cell membranes, muscle contractions › Support of bones (lack  osteoporosis ) › Neurotransmitter release for nervous system messages

 PHOSPHORUS › ATP › DNA

 IRON › Some chemoautotrophs—source of energy › Helps w/formation of chlorophyll  Fe deficient plants can’t photosynthesize properly › Component of hemoglobin (RBCs)  O 2 transport

 SODIUM › Some plants: helps bind CO2 for photosynthesis › Action potential in neurons  Nerve impulses  Na-K pumps › Glucose co-transport across membranes › Prokaryotes—movement of flagellum

 temp vs. time of day  water remains fairly stable