Metabolism

Metabolism  All chemical reactions in a cell → arranged into metabolic pathways  Intermediates in these pathways are called metabolites  Catabolic reactions (e.g. respiration) release energy  Anabolic reactions (e.g. photosynthesis) use up energy Leaf Structure  Phototropism → growth towards light  Large leaf surface area → captures more light  Thin leaves → few cell layer → more light captured by chlorophyll  Leaf mosaic increases leaf exposure to light  Internal Structure o Cuctile → reduces H2O loss by evaporation o Palisade mesophyll → chloroplast can move around cell for max light absorption o Spongy mesophyll → allows diffusion of gases through leaves o Phloem sieve tube → removes products of photosynthesis Chloroplast  Thylakoid membrane: light-dependent → large surface area o Associated with chlorophyll, accessory pigments, ETC, enzymes  Grana: stacks of thylakoid membranes o Enclose hydrogen reservoir used in chemiosmosis  Lamella: tubular extensions forming a network between grana  Stroma: RuBP carboxylase catalyses light independent reaction  Starch granule → insoluble storage carbohydrate product of photosynthesis Light Dependent Reaction  In Thylakoid Membrane / Granum  IMG 5-14-6 Chemiosmosis/Photophosphorylation produces ATP //H+ from photolysis remain in thylakoid space  ETC releases energy  Used to pump H+ from stroma into thylakoid space  By active transport and electrochemical gradient  H+ conc in thylakoid space > stroma  H+ ions pass back from space between two mitochondrial membranes  Through pores which are associated with the enzyme ATP synthetase  Energy from the ETC will be used to produce ATP  Diffuse down conc gradient across thylakoid membrane  Produces ATP by photophosphorylation Light Independent Reaction  In Stroma (Calvin Cycle)  IMG 5-14-6 Summary WITH IMG!!!!!!!!!!!!!!!  The light dependent reaction takes place in the chloroplast and is important to produce ATP and NADPH + H+. Both molecules and carbon dioxide (CO2) are needed in the light independent reaction (Calvin Cycle) to produce a hexose sugar, such as glucose, from RuBP.  Glucose is used to in the mitochondrion to produce the energy molecule ATP. NAD+ is also needed for respiration, but is not produced by photosynthesis.  PARP (Poly-ADP-Ribose-Polymerase) and PARG (Poly-ADP-Ribose-Glycohydrolase) are important if the plant is exposed to excessive stress factors (such as extreme temperatures). Note: knowledge about PARP and PARG is not required for your exam.  IMG  Picture 5-1 from Bayer research.  Genetic engineering improves crop yields,  Braving the drought [view article] Energy Transfer Ecological pyramids  Pyramids of numbers o Total number of organisms in a food chain at each trophic level o Highest number at the bottom (usually producers, then consumers) o Pyramid