Photosynthesis

• Plants turn solar energy into food
• Animals can't eat sunshine
• All the food we eat and the fossil fuels we burn are products of photosynthesis
• When animals eat plants and other animals


  The original solar energy is passed along the food chain
• Photosynthesis reaction


  6 CO2 + 12 H2O + sunlight
• Organisms that carry out photosynthesis

  • Plants
  • Cyanobacteria
  • Certain bacteria
  • Most algae
  • Phytoplankton
• Photoautotrophs or producers


  Organisms that make their own food and energy from the sun
• Consumers


  Depend on the products of photosynthesis that producers make to live
• During photosynthesis, plants produce glucose molecules when they convert light energy into chemical energy
• Glucose


  A sugar stored in the bonds of glucose, used for energy
• Plants produce sugars as a source of food and store excess glucose in their leaves
• All biological energy comes from glucose
• Plants can break apart glucose for energy and make it into carbohydrate chains called polysaccharides
• Polysaccharide chains in plants

  • Cellulose
  • Starch
• Cellulose


  Structural component of cell walls
• Starch


  Long-term energy store for plants
• Chloroplasts


  Plastids or plant cell organelles where photosynthesis occurs
• Chloroplasts have their own DNA different from plant DNA but similar to bacterial DNA
• Chloroplasts and mitochondria were engulfed by ancient eukaryotic cells through endosymbiosis
• Cyanobacteria are photosynthetic bacteria that undergo photosynthesis in lakes, ponds, and oceans
• Cyanobacteria lack chloroplasts
• Chloroplasts are full of thylakoids stacked in granum, lined by pigments like chlorophyll and carotenoids
• Chlorophyll harvests light energy packets when it absorbs sunlight
• Photosynthesis in plants happens in the chloroplasts
• Chloroplasts


  Full of thylakoids stacked in granum
• Components of thylakoid membranes

  • Pigments such as chlorophyll and carotenoids
• Photosynthesis


  1. Light energy from chloroplasts is captured and stored as ATP

  2. ATP is used to produce sugar for plant growth and life
• Chlorophyll


  Green pigment, most abundant, absorbs all wavelength colors except green which is reflected off, giving plants their green appearance
• Photosynthesis Reaction


  Divided into Dark reactions (light independent) and Light reactions (light dependent)
• Dark reactions


  Occur in the stroma of chloroplasts, fix carbon dioxide into glucose
• Light reactions


  Capture light energy to power photosynthesis, occur during the daytime in thylakoids, form protein complexes called Photosystem I and Photosystem II
• Energy Carrying Molecules


  • ATP, NADP+
• ATP


  Energy carrier molecule used in photosynthesis and cellular respiration, powers reactions in cells
• NADP+


  Can hold excited electrons from light energy, becomes NADPH, powers dark reactions
• O2 is a byproduct of photosynthesis, released through stomata of plants
• Stomata are little pores in leaves that open and close to let oxygen out and carbon dioxide in
• When water molecules break apart during photosynthesis, the remaining hydrogen atoms have a positive charge and are called protons
• Protons


  Kept inside the thylakoid by the thylakoid membrane, create a concentration gradient that powers ATP production
• ATP production


  Proteins use the passage of protons to attach a phosphate group to ADP, making ATP
• NADPH production


  Powered up by protons crossing the thylakoid membrane, carries energy to power the dark reactions or Calvin Cycle