Photosynthesis, Respiration, and the Carbon Cycle

    I. What is photosynthesis?
        A. Photosynthesis: captured light energy is transformed into chemical energy (stored as sugar).  An energy requiring process.
             Net equation:
                                                                                chlorophyll
                    6CO₂ + 6H₂O +energy as light-------------------------------> C₆H₁₂O₆ + 6O₂

                1. Carbon dioxide is the carbon source
                2. Light energy is the energy source
                3. Releases oxygen
        B. Plants, algae, and cyanobacteria.

    II. What is light?
        A. Sunlight is electromagnetic energy, also called radiation.
        B. Electromagnetic spectrum: gamma rays to radio waves
        C. Electromagnetic energy travels through the air in rhythmic waves.
        D. When these waves interact with matter, which is anything that occupies space and has mass, they behave as particles of energy called
              photons.
                1. The shorter the wavelength the greater the energy
        E. Visible light = 400 to 700nm.  Region used to drive photosynthesis and the same region humans see.

    III. Chloroplasts
        A. Sites of photosynthesis in plants.
        B. Found in mesophyll cells (specifically the palisade mesophyll cells).
        C. Chloroplast structure:
                1. Thylakoids and Grana
                2. Stroma
        D. Pigments absorb light
                1. Only light that is absorbed can produce a biological effect in an object.
                2. Pigments: substances that absorb light
                3. Two primary pigments in plant chloroplasts:
                        a) Chlorophyll a
                        b) Chlorophyll b
                4. Minor pigments: carotenoids
                5. Absorption spectrum
                6. Action spectrum
        E. What colors are the most and least effective for driving photosynthesis?

    IV. How photosynthesis actually works
        A. It occurs in two stages:
                1. Light reactions: light dependent reactions
                2. Dark reactions: light independent reactions or Calvin cycle
        B. Light reactions
                1. Occurs in the thylakoid membranes
                2. Two high energy compounds are made: NADPH and ATP
                3. Oxygen is made. (from the splitting of water)
        C. Dark reactions
                1. occurs in the stroma
                2. uses light reaction products and carbon dioxide to make sugar (process called carbon fixation).
                3. reactions are controlled by enzymes.

    V. Respiration
        A. Respiration: sugars (chemical energy) are broken down to obtain the energy they contain. An energy releasing process.

                            C₆H₁₂O₆ + 6O₂  ---------------------------->  6CO₂ + 6H₂O + heat + energy (as ATP)

        B. Occurs in the cytosol and mitochondria.
        C. All organisms respire!

    VI. Energy is linear
        A. Chemical elements are recycled, but energy is not.
        B. Food chains demonstrate the linear nature of energy.
                1. Producers (autotrophic)
                2. Primary consumers (heterotrophic)
                3. Secondary consumers (heterotrophic)
                4. Decomposers (heterotrophic)

    VII. Carbon Cycle
        A. Carbon itself is recyclable.  CO2 in air converted into organic compounds by photosynthesis in plants, using light energy.  Energy and
             carbon in organic compounds passed through food chain to herbivores and carnivores.  Organic compounds converted back to CO2 by
             respiration in plants, animals, and microbes in soil.