5: photosynthesis

• Photosynthesis: the production of sugar in plants using carbon dioxide and water in the presence of light. Solar energy is used to produce chemical energy which is used to produce organic molecules
• Label the ratios of the reactants and the products of photosynthesis

  A) 6

  B) 12

  C) 1

  D) 6

  E) 6

  
• Within photosynthesis, 6 carbon dioxide molecules and 12 water molecules combine to make 1 glucose molecule, 6 water molecules, and 6 oxygen molecules.
• Photosynthesis occurs in plants and trees, algae and kelp, and photosynthetic bacteria
• Plants can only respond to light in the visible spectrum
• The two forms of chlorophyll are chlorophyll a and chlorophyll b
• Carotenoids are orange and yellow pigments that absorb light around the 480-500 nm wavelength.
• Chlorophyll absorbs blue light around the 440 nm wavelength and red light at the 680-700 nm wavelength.
• In fall, chlorophyll is broken down and the carotenoid pigments are visible in leaves.
• Carotenoids are anti-oxidants that reduce oxidative damage due to sunlight and UV rays
• Chlorophyll are green pigments contained within chloroplasts
• Chloroplasts are found in the mesophyll cells of leaves and surrounded by a double layer of cell membranes.
• Within chloroplasts are stacks of granum that are surrounded by a thykaloid membrane. Space between granum are called stroma.
• Granum absorbs all visible light aside from green light, which is instead transmitted.
• Light energy is packaged into photons that strike the chlorophyll, causing it to emit higher energy level electrons.
• In light reactions, ADP and NADP are combined with P to form ATP and NADPH to provide energy for the next step in photosynthesis. Oxygen is also released from water.
• Following the light reactions, the Calvin cycle is a light independent process which uses the energy generated by the light reactions to form carbon molecules from carbon dioxide.
• A photosystem is a light-harvesting complex which is an arrangement of chlorophyll and pigment molecules. It contains the primary electron acceptor pheophytin.
• Photosystem I and II are contained within the thylakoid membrane.
• Photosystem I absorbs light within the range of 700 nm (P700)
• Photosystem II absorbs light within the range of 680 nm (P680).
• Electrons released from the splitting of water by light photos reach P680 first, then the chlorophyll energizes electrons to the primary electron acceptor pheophytin
• After being energized to the pheophytin, electrons are transferred down the electron transport chain, going from plastoquinone (Pq), cytochrome complex (Cc), and to plastocyanine (Pc).
• At the cytochrome complex, energy from the electrons is used to generate ATP.
• After going down the electron transport chain, light energy strikes PS I (P700) is transferred to the primary electron acceptor.
• After being transferred to the primary electron acceptor in PS I (P700), the electrons continued down the electron transport chain to Ferredoxin (FD), where their energy forms NADPH using NADP reductase.
• The end result of the Calvin cycle is the release of water to produce ATP and NADPH and the production of oxygen.
• NADP reductase forms NADPH within photosystem I
• Label this metaphorical diagram

  A) photon

  B) photosystem II

  C) ATP

  D) ATP

  E) photon

  F) photosystem I

  G) NADPH

  
• Cyclic electron flow occurs when electrons from Ferredoxin are transferred back to the Cytochrome complex instead of moving on to NADP reductase, resulting in no NADPH being formed but the continued production of ATP

  
• Cells undergo cyclic electron flow if there is enough NADPH or if the cells needed more ATP production.

  
• Chemiosmosis: ATP synthase facilitates ATP production which is driven by the flow of protons through the thylakoid membrane and into the stroma of the chloroplast.
• Label this diagram of photosynthesis

  A) photosynthesis II

  B) Pq

  C) Cytochrome complex

  D) Pc

  E) photosystem I

  F) FD

  G) NADP reductase

  H) ATP synthase

  
• The Calvin cycle (C3 cycle or carbon fixation) converts carbon dioxide to sucrose using ATP and NADPH from the light reactions as energy sources within the stroma of chloroplasts
• There are three steps to the Calvin cycle: carbon fixation, reduction, and regeneration of the CO2 acceptor (RuBp)
• Carbon fixation is the first step of the Calvin cycle, starting with RuBp adding one CO2 molecule to form 2 3-phosphoglycerate. This reaction is catalysed by Rubisco
• Reduction is the second step of the Calvin cycle which requires ATP to produce 1,3-Biphosphoglycerate. NADPH is used to form glyceraldehyde-3-phosphate which goes on to form sugar.
• Regeneration is the third step of the Calvin cycle where ATP is used to regenerate RuBP to continue the cycle again
• The net energy usage of the calvin cycle is 18 ATP and 12 NADPH.
• Label this diagram of the Calvin cycle

  A) Carbon fixation

  B) Reduction

  C) Regeneration of the CO2 acceptor

  D) rubisco

  E) ATP

  F) NADPH

  G) ATP