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Cell energy Ch.9 • All living organisms must be able to produce energy, store the energy for future use and use energy. Cell processes that require energy • • • • Active transport Movement Cell division Production and storage of proteins • Cells use energy to maintain homeostasis ATP • Molecule in your cells that is a quick source of energy for any organelle in the cell that needs it. • This energy is stored in the chemical bonds of the molecule ATP • Adenosine Triphosphate is composed of an adenosine molecule with 3 phosphate groups attached. • AMP - adenosine monophosphate small amount of energy • ADP - adenosine diphosphate - more substantial amount of energy • ATP - When bond is broken, a great amount of energy is released & the cell can use the energy for activities. ADP can then reform ATP by bonding with another phosphate group Photosynthesis • The process plants use to trap the sun’s energy and build carbohydrates, called glucose, that store energy. • Occurs in 2 phases 1. Light-dependent reactions 2. Light-independent reactions • 6CO2 + 6H2O C6H12O6 + 6O2 Light-dependent reactions • Convert light energy into chemical energy • ATP produced in LDR are used to fuel LIR that produce glucose Chloroplasts • Cell organelle where photosynthesis occurs • Within chloroplasts, thylakoid discs contain pigments • Most common pigment is chlorophyll • Light-dependent reactions take place in the thylakoid discs Chlorophyll • Absorbs most wavelengths of light except green which it reflects, giving leaves a green appearance Light-dependent reactions • Requires sunlight • Sunlight strikes molecules in thylakoid membrane & light energy is transferred to electrons • These electrons are passed to an electron transport chain Electron transport chain • A series of proteins embedded in the thylakoid membrane • Each protein passes energized electrons along from protein to protein • At each step the electron loses energy • ETC allows small amounts of energy to be released at time • This energy can be used to form ATP • This energy is not wasted, the electron is transferred to the stroma of the chloroplast • NADP+ is used & becomes NADPH Photolysis • Electrons must be restored to chlorophyll because many leave with NADPH • To replace the lost electrons, molecules of water are split through a process called photolysis Light-independent reactions • Does not require light • Calvin cycle • Series of reactions that use carbon dioxide & ATP from Lightdependent Reactions to form carbohydrates • Takes place in the stroma of the chloroplast • We know that plants use sunlight energy to split water (H2O) into hydrogen and oxygen. • The hydrogen is added to the carbon dioxide to make CARBOHYDRATES such as glucose. • The oxygen produced from this splitting of water is released into our atmosphere. • We summarise this using a chemical equation: 6 CO2 + 6 H20 ------------ C6H12O6 + 6 O2 carbon water glucose oxygen dioxide Cellular Respiration • The process by which mitochondria break down food molecules to produce ATP 3 Stages 1. Glycolysis (anaerobic) 2. Citric acid cycle (aerobic) 3. Electron Transport Chain (aerobic) • Anaerobic – no oxygen required • Aerobic – oxygen required Glycolysis • A series of chemical reactions in the cytoplasm of a cell that break down glucose into 2 molecules of pyruvic acid • Uses 2 molecules of ATP to start & only produces 2 molecules of ATP per glucose broken down • Not very efficient but can occur in the absence of oxygen • Uses an electron carrier called NAD+ • NAD forms NADH when it is carrying an electron • Following glycolysis, the pyruvic acid molecules move to the mitochondria Citric Acid Cycle • Occurs in mitochondria • One molecule of ATP is produced for every turn of the cycle • 2 electron carriers are used – NAD+ – FAD • Electron carriers pass energized electrons along to the electron transport chain in the inner membrane of the mitochondrion. Electron Transport Chain • NADH & FADH2 pass energized electrons from protein to protein within the membrane slowly releasing small amounts of the energy contained within the electron • Some energy is used to form ATP & some is used to pump H+ ions into the center of the mitochondrion. • Mitochondrion inner membrane becomes positively charged because of the high concentration of positively charged hydrogen ions. • Exterior of membrane is negatively charged which further attracts hydrogen ions • Inner membrane of the mitochondrion forms ATP from this electrochemical gradient of H+ ions across the membrane. • Overall ETC produce 32 ATP molecules Fermentation • When your cells are without oxygen for a short period of time, an anaerobic process called fermentation follows glycolysis. • Two major types – Lactic acid fermentation – Alcoholic fermentation