Biology 12

Respiration revision Glycolysis Glucose  pyruvate + 2 ATP Fermentation (plants) Pyruvate  alcohol + carbon dioxide Fermentation (animals) Pyruvate  lactic acid Aerobic respiration Glucose + oxygen  carbon dioxide + water + energy (36 – 38 ATP)

Photosynthesis Uses light energy to convert inorganic molecules to organic molecules Occurs in the chloroplasts of plant cells and some protists and the cytoplasm of cyanobacteria Occurs as a series of reactions, involving many different enzymes Involves light dependent and light independent reactions (the Light and Dark reactions)

Photosynthesis 2 Net equation: carbon dioxide + water + solar energy  glucose + oxygen + water ATP and ADP are used to transfer energy NADP is used as a hydrogen carrier

Where it happens

Structure of the chloroplast

Light reaction Occurs in the grana (thylakoid membrane) of the chloroplast Inputs are light and water Light strikes photosystem II Electrons pass along until they reach the primary electron acceptor Water is split into hydrogen ions and oxygen atoms Electrons pass down the electron transport chain to photosystem I, forming ATP The three products of the light reaction are NADPH, ATP, and O 2 NADPH & ATP are then used in the Calvin Cycle

The Grana – photosystems I and II and the electron transport chain

ATP and ADP Act as chemical batteries Carry and release small amounts of energy energy adenosine phosphate adenosine ATP ADP

Carrier proteins Carry hydrogen ions to electron transport chains NADP  NADPH + H +

Light independent (Dark) reaction Occurs in stroma of the chloroplast Inputs are NADPH and ATP from the light reaction, and CO 2 First step is carbon fixation A series of reactions lead to the production of water, NADP+ and ADP, and sugar NADP+ and ADP return to the light reaction The carbon of the sugar product comes from CO 2

Calvin cycle

Summary of reactions

Summary of photosynthesis Light dependent reaction Occurs in the grana Water is split into hydrogen ions and oxygen Inputs are light and water Outputs are ATP, hydrogen ions and oxygen Involves photosystems I and II and electron transport chain Light independent reaction Occurs in the stroma Carbon is fixed Inputs are ATP, hydrogen ions and carbon dioxide Outputs are glucose, water and ADP Involves the Calvin cycle

Comparison between respiration and photosynthesis RespirationPhotosynthesis InputsOxygen & glucoseCarbon dioxide, light, water ProductsCarbon dioxide, water & energy (ATP) Oxygen, glucose & water Type of cellsAll cellsPlants & some protists & bacteria Location in cellsCytoplasm (anaerobic) & mitochondria (aerobic) Chloroplast Where energy comes from Carbon compounds (chemical breakdown) Light Role of ATPEnd productCarries energy of light reactions into dark reactions Names of reactions Glycolysis, fermentation, Krebs cycle Light reactions – Photosystems I & II & electron transport chain Dark reactions – Calvin cycle