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BIOLOGY: Class Notes #1= Photosynthesis Name______________________ Date_____________Per.______ Autotrophs vs. Heterotrophs Autotrophs make their own food/energy Ie) Plants use the light energy from the sun to produce food Heterotrophs eat other things for food/energy Ie) Animals cannot use the sun’s energy directly so they consume food Mushrooms decompose other organisms The chemical process that produces food for autotrophs is photosynthesis. The breaking down of food to release energy for cell work is cellular respiration. Chemical equation for PHOTOSYNTHESIS: Chlorophyll / enzymes Chemical equation for RESPIRATION: C6H12O6 + 6O2 6CO2 + 6H2O + 36ATP (38 ATP, in some prokaryote cells) C reduced + O oxidized ----------> C Oxidized + O reduced II. The molecule which temporarily stores energy for the cell until it is needed is called adenosine triphosphate (ATP). This molecule consists of three different parts: adenosine adenine: a nitrogen containing double ring molecule ribose: a five carbon sugar 3 phosphates: the inorganic portion of the molecule, containing the elements, P and O The chemical bonds joining one phosphate to the next are high energy bonds. It takes a lot of energy to form them and a lot of energy can be released if they are broken. Energy from food ADP + P ----- ATP (enzyme that catalyzes this reaction is ATP Synthetase) ATP ADP + P + energy to do cell work ( enzyme that catalyzes this reaction is called ATPase) 2 PLANTS Plants have an organelle called chloroplasts. This organelle contains a pigment called chlorophyll which absorbs the light energy from the sun (these give them their green color). Photosynthesis occurs in the chloroplasts. Most photosynthesis occurs in the green leaves and some occurs in the green stems. Photosynthesis is a process in which green plants convert energy from sunlight into chemical energy! In the chloroplast there are membranes called thylakoids which are arranged in stacks called grana. The space outside the thylakoids is called the stroma. 2 parts to chloroplast: a. Grana- Contains chlorophyll. Looks like coin stacks. Where light dependent reactions occur. b. Stroma- No chlorophyll. Surrounds grana. Where sugar is made. Where light independent (DARK) reactions occur. Photosynthesis is in 2 parts: 1) Light Dependent Reactions= (AKA Light Reactions) take place in the thylakoids 2) Light Independent Reactions= (AKA Calvin Cycle) (Dark) take place in the stroma Location of Photosynthesis 3 1 —Light Reactions Sunlight hits the chlorophyll in a leaf. This light energy energizes electrons in the chlorophyll which are passed into the Electron Transport Chain. These high energy electrons move through the ETC freeing energy with each step in the form of ATP. Water molecules are split to replace the electrons lost from the chlorophyll (in the form of Hydrogen) & Oxygen from the water molecule is released. (This is what we breathe!) Hydrogen atoms from the water are picked up the enzyme NADP+ which then becomes NADPH. NADPH carries the hydrogen to the next step (Calvin Cycle = Dark Reaction) and is then returned to NADP+. st Summary The products of the light reaction are Oxygen (waste product from splitting water), NADPH (carrying hydrogen to the next step), & ATP (which is carrying energy to the next step). 4 2 —Light Independent Reactions (AKA Calvin Cycle) = (DARK Reaction) CO2 enters the cycle from the atmosphere and combines with carbon molecules which are already in the cycle. nd (The plant “breathes” in CO2 through opening in the leaves called stomata. ) The ATP and NADPH from the Light Reactions are used to give these new carbon molecules more energy. (ATP becomes ADP and goes back to the light reactions in order to become ATP again. NADPH becomes NADP+ and goes back to the light reactions to get more hydrogen.) Some of these molecules are used to produce sugars, lipids, amino aids, and other compounds needed for plant metabolism and growth. (This is where the six-carbon glucose is made!) Left over carbon molecules cycle back around and join with new CO2 coming in. Summary The Calvin Cycle uses ATP and NADPH from the light reactions & CO2 from the environment to produce high-energy sugars (glucose). Formula 6CO2 + 6 H2O C2H12O6 + 6O2 + 6H2O CO2 from air H2O from ground Glucose (C6H12O6) is a CARBOHYDRATE – Carbon comes from CARBON DIOXIDE! O2 out (what we breathe) Factors affecting the rate of photosynthesis 1)Sunlight - its Intensity & wavelength. 2) H2O and CO2 – availability 3) Temperature (0 –35O C) 4) Minerals 5) Any factor that influences the production of chlorophyll, enzymes, or energy carriers(ATP and NADPH). The rate of photosynthesis will always correspond to that factor which is in least supply. Its rate will only increase when its supply is increased.