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Transcript
How organisms get energy Autotrophs Organisms that make their own energy by absorbing light from the sun (photosynthesis) Plants and some fungi Heterotrophs Organisms that get energy by eating other organisms Adenosine Triphosphate (ATP) Energy used by cells is called ATP ATP is made of a sugar (ribose), (adenine), and 3 phosphate groups (triphosphate) Adenosine Diphosphate (ADP) has 2 phosphate groups The chemical bonds between the phosphate groups contain A LOT of energy ATP has more energy than ADP because it has more phosphate groups ATP Section 8-1 Adenine Ribose 3 Phosphate groups Figure 8-3 Comparison of ADP and ATP to a Battery Section 8-1 ADP ATP Energy Adenosine diphosphate (ADP) + Phosphate Partially charged battery Energy Adenosine triphosphate (ATP) Fully charged battery Figure 8-3 Comparison of ADP and ATP to a Battery Section 8-1 ADP ATP Energy Adenosine diphosphate (ADP) + Phosphate Partially charged battery Energy Adenosine triphosphate (ATP) Fully charged battery Photosynthesis Photosynthesis - the process where plants use sunlight to convert water and CO2 to make sugars to use for energy Oxygen (O2) is also created as a waste product Photosynthesis occurs in the chloroplasts of plant cells 6CO2 + 6H2O + sunlight→ C6H12O6 + 6O2 Carbon dioxide + water + sunlight = sugars + oxygen Photosynthesis: Reactants and Products Light Energy Chloroplast CO2 + H2O Sugars + O2 Chloroplasts Chloroplasts consist of thylakoids and stroma Thylakoids Stacks of sac-like membranes where light-dependent reactions occur Stacks are called grana Pigments are molecules that can capture sunlight Chlorophyll is the main pigment of plant cells Appears green because it does not absorb green light, but reflects it Thylakoids organize chlorophyll and other pigments into light-collecting units called photosystems Stroma The area outside the thylakoids Where the light-independent reactions, or dark reactions, occur Light-independent reactions are called the Calvin cycle Electron Carriers Sunlight gives electrons in chlorophyll a lot of energy In order to move these high-energy electrons, they need a special molecule called an electron carrier The process of moving electrons is called electron transport and the carriers themselves are called the electron transport chain NADP+ is an electron carrier NADP+ can carry 2 high-energy electrons and a hydrogen ion (H+) When NADP+ carries H+ and 2 electrons, it forms NADPH NADPH carries electrons to parts of the cell where they are needed to help build needed molecules, such as sugars Concept Map Section 8-3 Photosynthesis includes Lightdependent reactions Calvin cycle use take place in Energy from sunlight Thylakoid membranes to produce ATP NADPH O2 takes place in Stroma uses ATP NADPH of to produce Chloroplasts High-energy sugars 3 Stages of Photosynthesis Stage 1: Light Capturing (part of light-dependent reactions) Pigments capture sunlight that excites electrons Electrons are supplied by H2O Products of light capturing are high-energy electrons, H+ ions, and oxygen (O2) Oxygen is a waste product (not needed by plant cell) Stage 2: Light-Dependent Reactions Utilizes H+ ions and high-energy electrons to turn ADP and NADP+ into ATP and NADPH Stage 3: Calvin Cycle Utilizes ATP and NADPH to produce sugars that hold more energy than ATP Sunlight H2O CO2 Chloroplast Chloroplast NADP+ ADP + P LightDependent Reactions Calvin Cycle ATP NADPH O2 Sugars Light-Dependent Reactions Light is captured by the pigments in photosystem II Light excites electrons (from chlorophyll, provided by H2O) Electrons move along the electron transport chain to photosystem I. As electrons move along the chain, their energy is used to move H+ ions from the stroma into the thylakoids Light is captured in photosystem I to re-energize the electrons. NADP+ picks up 2 of these electrons and a H+ ion to form NADPH Light-Dependent Reactions cont. Remember that while electrons move along the chain, H+ ions are pumped into the thylakoid Eventually, the thylakoid fills up with H+ ions, leaving inside the thylakoid positive and outside the thylakoid negative H+ ions then move through a protein channel called ATP synthase from inside the thylakoid to outside the thylakoid This movement causes ATP synthase to spin As it spins, it adds a phosphate group to ADP, creating ATP Photosystem II Hydrogen Ion Movement ATP synthase Inner Thylakoid Space Thylakoid Membrane Stroma Electron Transport Chain Photosystem I Calvin Cycle 6 CO2 molecules combine with six 5-carbon molecules to form twelve 3-carbon molecules The twelve 3-carbon molecules are energized by ATP and NADPH 2 of the 3-carbon molecules are removed to make sugars, lipids, amino acids, or other molecules the plant cell needs The ten 3-carbon molecules that are left over are converted back into six 5-carbon molecules to start the Calvin cycle all over again CO2 Enters the Cycle Energy Input 5-Carbon Molecules Regenerated 6-Carbon Sugar Produced Sugars and other compounds