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York University
BIOL 1500

Biology Chapter 4 Notes: Energy Energy: capacity to do work; two types are kinetic and potential energy; can be captured, converted, lost in the form of heat; can change but never disappear; conversion of energy is not perfectly efficient and invariably includes the transformation of some energy into heat Kinetic energy: energy of moving objects Potential energy: stored energy or the capacity to do work that results from an object's location or position; ex. water dam; chemical energy (storage of energy in chemical bonds) Adenosine triphosphate (ATP): must be captured in the bonds of this molecule; free-floating, found in cells that act like a rechargeable battery; temporarily stores energy that can then be used for cellular work; ATP connects the timing of energy needed/provided; small sugar molecule (ribose) + adenine + 3 phosphate groups; release of energy = separation of a phosphate; kinetic energy into potential when phosphate group attaches to ADP Photosynthesis • Carbon dioxide + water + sunlight --> oxygen + sugar • Pigments: light-absorbing molecules • light energy (kinetic) made up of packets called photons --> primary photosynthetic pigment (chlorophyll a) or chlorophyll b, carotenoids --> photons excite the electrons in the chlorophyll --> electron gains energy, potential energy in chlorophyll molecule increases --> returns to resting state or passed to another molecule (primary ways energy moves through cells) • "Photo" reactions: happens in the thylakoid; primary electron acceptor grabs them and sends them to electron transport chain; water molecules are split and oxygen and hydrogen are released as by-products to replace the electrons sent to transport chain; electrons move through the chain and energy levels lower; energy powers proton pumps and move hydrogen ions from stroma to thylakoid; protons rush out of thylakoid with great kinetic energy which can be used to build ATP; electrons passed to second electron transport chain; in the end, electrons passed to molecule called NADP+ creating NADPH • ”Synthesis" reaction (calvin cycle): 1. fixation: rubisco (most common protein on earth) pluck carbon from air and fix them to a visible organic (carbon-containing) molecule within the chloroplast; 2. sugar creation: newly built molecule is chemically modified; phosphate from ATP added and some high energy electrons from NADPH and creates glyceraldehyde 3-phosphate (G3P); 3 carbon molecules from carbon dioxide must be fixed into G3P to synthesize six-carbon sugars (glucose and fructose); 3. Regeneration: other G3P molecules are regenerated into the origin
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