Characteristics of photosynthesis

• endergonic reactions = chemical reactions the require the input of energy
• exergonic reaction = chemical reactions that involve the release of energy
• the cells of all organisms use the chemical energy by breaking down complex compounds into simpler compounds
• ATP is formed when ADP and inorganic phosphate combine during photosynthesis and cellular respiration
• autotrophs = produce their own food from inorganic compounds (producers)
• heterotrophs = obtain organic compunds by consuming other organisms (consumers)
• photosynthesis can also be called carbon fixation as carbon atoms from CO2 gas in the atmosphere are incorporated into organic molecules (glucose)
• chlorophyll = a green pigment that is able to absorb different light wavelengths except for green
• accessory pigments cannot pass their absorbed energy directly to the photosynthesis biochemical pathway, it is transfered to chlorophyll to then be used in photosynthesis
• photosynthesis word equation

  carbon dioxide + water -light energy> glucose + water + oxygen
• photosynthesis chemical equation

  6CO2 + 12H2O -light energy> C6H12O6 + 6H2O + 6O2
• in vascular plants chloroplasts are in mesophyll cells
• chloroplasts have an inner and outer membrane and inside the membranes is a fluid matric called stroma and a thykaloid membrane
• first stage of photosynthesis is the light dependent stage in the thykaloid membrane
• chlorophyll are embedded in the thykaloid membrane where they absorb light
• light dependent reactions occur in the grana in chloroplasts
• chlorophyll captures solar energy and uses it to produce ATP molecules and NADPH
• NADPH = nicotinamide adenine dinucleotide phosphate
• photolysis = water is split into hydrogen ions and oxygen gas
• when ATP and NADPH is produced photolysis occurs
• the light independent stage is the second stage of photosynthesis
• the light independent stage requires the ATP and NADPH produced in the light dependent stage
• light independent reactions occur in the stroma of chloroplasts
• energy is used to combine CO2 with hydrogen ions to form glucose and water
• Calvin cycle is the main stage of the light independent reactions
• product of the Calvin cycle is a three-carbon carbohydrate, glyceraldehyde-3-phosphate (GAP)
• in the cytoplasm two GAP molecules combine to create glucose
• the remaining GAP molecules are recycled into RuBP
• RuBP = riboluse 1, 5-biphosphate
• RuBP is the starting molecule of the light independent stage
• Light dependent reactions:

  • captures light
  • stores energy in bonds of ATP and NADPH
• Light independent stage:

  • ATP is broken down to ADP
  • releases energy for th eplant to use
  • electrons from NADPH convert CO2 to glucose
• C3 plants fix carbon directly from CO2 and Rubisco removes the carbon from carbon dioxide and adds it to a 5-carbon molecule, that molecule is then split into two 3-carbon molecules that can be used by the cell
• 5- carbon molecule amde in C3 plants = ribulose biphosphate
• 3-carbon molecule made in C3 plants = phophogucerate
• C4 plants use PEPCase to capture CO2 in the mesophyll cells where it is added to ther carbons to form a 4-carbon molecule which is converted to pyruvate and transported to bundle sheath cells where it releases CO2 for carbon fixation by Rubisco in the Calvin cycle
• 4-carbon molecule made in C4 plants is oxaloacetate
• Rubisco is an enzyme
• CAM plants open their stomata at night to collect CO2 and stores it in vacuoles as malic acid, during the day malic acid is transforted to chloroplasts for photosynthesis
• photosynthesis turns an inorganic molecule (carbon dioxide) into an organic molecule (glucose)