Transcript Document
Ch. 7 Photosynthesis Using Light to Make Food 7.1 -7.5 • What is photosynthesis? • Light energy (from sun) is used to make sugar & other food from CO2 & H2O • Can too much sunlight harm a plant? • Yes. It can overwhelm the plant. How it all happens • Is there a chemical equation for photosynthesis? • Yes. Carbon dioxide (CO2) is reduced to glucose & water (H2O) is oxidized to oxygen gas (O2) • Where does the O2 come from? • From water, H2O • What is an “autotroph?” • It means a “selffeeder” • Are all plants autotrophs? • Yes, they make their own carbohydrates from CO2 which is a great fuel & don’t eat other organisms to live. Examples of autotrophs • Even thought they are autotrophs, what do plants require to synthesize sugar? • Light=energy, CO2 & H2O to make sugar, this is endergonic so it stores the energy from light (Ch.5) • Oak tree, cactus, Kelp (a large alga photosynthetic protist), and photosynthetic bacteria Producers • Why are plants considered producers of the biosphere? • They make the biosphere’s organic food supply from raw material (CO2) • What is the biosphere? • The portion of Earth that is living, all life & where it lives • Are plants the only producers? • No, some bacteria, archaea and protists also make food from inorganic materials. All organism that use light energy to make food are photosynthetic autotrophs. Where it all happens • Where does photosynthesis take place? • In eukaryotic organelles called Chloroplasts (photosynthetic bacteria have no organells) • Why are plants green? • Chlorophyll, a pigment in the chloroplasts. It absorb all colors but green,(which reflect back at you) the light energy and then chloroplasts convert that into food. Parts of a leaf • Where are chloroplasts concentrated? • In the mesophyll cells, green tissue on the interior of leaf. • How does gas enter & exit plants? (CO2 & O2) • Stomata (stoma, singular), the tiny pores on the leaf. Parts of a Chloroplast • Stroma, is a thick fluid, found in the inner membrane. What happens there? • Stroma is the location of the Calvin cycle (CO2 -> sugar) • Thylakoids are suspended in the stroma. What do they do? • Thylakoids are the Location of light reaction. They are stacked into grana and contain the chlorophyll, that capture light energy. • Where does O2 gas come from? • It comes from water (H2O) and not carbon dioxide (CO2) • What is the ratio of water molecules needed for each molecule of O2 gas • 2:1, 2 water (H2O) molecules for every molecule of O2, • Why is photosynthesis called Redox? • Leo goes ger - lose an electron oxidation / gain an electron reduction • Water is split apart yielding O2, oxidized, the loss of electrons along with hydrogen ions (H+) • Carbon dioxide is reduced to sugar, gaining electrons along with hydrogen ions (H+) • What is the opposite of photosynthesis? • The energy releasing process of cellular respiration. Using energy in glucose by oxidizing sugar and reducing O2 to H2O. Photosynthesis occurs in two stages linked by ATP & NADPH • • • • • What happens in the light reaction? Light energy is absorbed by chlorophyll (in thylakoids) and covert it into chemical energy (ATP & NADPH) (O2 is waste product) What happens in the Calvin Cycle and why has it been called the dark reaction? Occurs in stroma of chloroplast, series of reactions that assemble sugar using CO2 & energy from light reaction. Called the dark reaction because it does not require light directly. Does run during day cause of ATP & NADPH from light cycle.