Q4_GenBio1_Photosynthesis

• Radiant energy

  Energy that enters the living world in the form of light from the sun
• Photosynthetic organisms

  Plants, algae and some bacteria that can harness sunlight to manufacture food
• Energy is defined as the capacity to do work
• Laws of energy


  • Law of conservation of energy - energy can neither be created nor destroyed, it can only be converted from one form to another
  • Law of entropy - energy is spontaneously converted from higher to lower quality, lost mostly in the form of heat
• Photosynthesis


  Plants use light energy to manufacture organic food from carbon dioxide and water
• Fossil fuels


  • Coal
  • Petroleum (oil)
  • Natural gas
• Use of biofuels allows us to grow our fuel source and use the energy obtained through photosynthesis and stored in food by plants
• The plant that is the source of fuel can also help remove from the air the carbon dioxide released by biofuel combustion
• Biodiesel


  Fuel obtained by converting hemp oil with caustic lye dissolved in methanol
• Biodiesel releases no sulfur by-products, produces slightly more nitrogen oxide and has 80 percent less emissions than gasoline
• Petrodiesel and gasoline are drawn from fossil fuels which are nonrenewable resources
• Mining and burning of fossil fuels can deplete the limited hydrocarbon reserves of the earth and contribute to global warming
• Technology has allowed man to exploit plants as alternative source of fuel that is renewable and more environment-friendly
• Leaves of plants


  • Enable plants to perform photosynthesis
• Phyllotaxy (leaf arrangement on stem)


  • Alternate
  • Opposite
  • Whorled
• Leaf blade or lamina


  The main part of the leaf, usually thin, flat, broad and green in color due to chlorophyll
• Simple leaf


  Leaf with just one piece of lamina
• Compound leaf


  Leaf with lamina divided into small pieces called leaflets
• Pinnately compound leaf


  Leaflets arranged along an extended axis called the rachis
• Palmately compound leaf


  Leaflets attached to a contracted rachis at the tip of the petiole
• Leaf structure


  • Upper and lower epidermis, vein made of vascular tissues, middle mesophyll layers
• Epidermis


  Protective layer of cells covering the leaf, coated with waxy cutin
• Stomata


  Pores in the lower epidermis for gas exchange and water loss
• Vein


  Made of vascular tissues - xylem for water transport, phloem for food transport
• Palisade mesophyll


  Compactly arranged, cylindrical cells with numerous chloroplasts, primary photosynthetic region
• Spongy mesophyll


  Loosely arranged, irregularly shaped cells with large intercellular spaces and fewer chloroplasts
• Land plants generally have more stomata in the lower epidermis than in the upper epidermis, which is beneficial for the plants
• Light


  A small part of the continuous radiant energy from the sun, exhibits both particle and wave properties
• Photon


  Unit of light energy
• Wavelength


  Distance between consecutive peaks of light waves
• Visible light


  Part of the electromagnetic spectrum visible to the naked eye, with wavelengths between 390 to 760 nanometers
• Photosynthesis utilizes only the visible light portion of the electromagnetic spectrum where photons have just the right amount of energy to excite electrons without harming the cells
• Absorption, reflection, transmission of light


  When light strikes an object, it may be absorbed, reflected or transmitted
• Chlorophyll


  Green pigment in plants that does not absorb green light, making leaves appear green
• Plastids


  Cellular structures in plant cells that generally hold pigment molecules
• Chloroplasts


  Plastids that contain the green pigment chlorophyll
• Carotenoid pigments


  Pigments like carotenes and xanthophylls found in some plastids
• Absorption


  Light is transformed from one form to another
• Reflection


  Part of light that is not absorbed
• Transmission


  Part of light that is not absorbed