II: Cellular Energetics

• Gravitropism


  How plants respond to gravity (the pull of gravity), where roots exhibit positive gravitropism (grow towards gravity) and shoots exhibit negative gravitropism (grow away from gravity)
• Photoperiodism


  How plants respond to the light/dark cycles and the seasonal changes in the length of day
• Thigmotropism


  How plants respond to touch, e.g. ivy growing around a support
• Animals also often respond to touch
• Bioenergetics


  The study of how energy from the sun is transformed into energy in living things
• During chemical reactions, bonds are either broken or formed, involving energy
• Adenosine Triphosphate (ATP)


  The molecule that provides energy for almost everything an organism does
• ATP formation


  1. Cell takes ATP molecule

  2. Splits off third phosphate

  3. Forms adenosine diphosphate (ADP) and loose phosphate

  4. Releases energy
• Organisms can use exergonic processes that increase energy, like breaking down ATP, to power endergonic reactions, like building organic macromolecules
• Cellular respiration


  The process of breaking down glucose and making ATP
• Photosynthesis


  Carbon dioxide + water -> glucose + oxygen
• Chloroplasts


  • The primary sites of photosynthesis in plant leaves
• Photosynthesis stages


  1. Light reactions

  2. Dark reactions
• C3 photosynthesis


  The type of photosynthesis utilized by the majority of plants, producing a 3-carbon compound
• C4 photosynthesis


  A type of photosynthesis that produces a 4-carbon intermediate compound, allowing plants to thrive in low light/water environments
• Cellular respiration


  Organisms combine oxygen with foodstuff molecules, diverting the chemical energy into life-sustaining activities and producing carbon dioxide and water as waste
• Aerobic respiration


  1. Glycolysis

  2. Formation of acetyl-CoA

  3. Krebs cycle

  4. Oxidative phosphorylation
• Anaerobic respiration


  Glycolysis only, producing lactic acid or ethanol