Biology Concepts & Applications 10th Edition - Chapter 6 PDF

Biology Concepts & Applications 10 Edition Chapter 6 Where It Starts — Photosynthesis Copyright © 201...

Biology Concepts & Applications 10 Edition Chapter 6 Where It Starts — Photosynthesis Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. khan academy help Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a  6.1 Overview of Photosynthesis Energy flow through ecosystems begins when photosynthesizers capture sunlight and convert it to chemical energy Unlike light, chemical energy can power the reactions of life, and can be stored for use at a later time Photosynthesis summary: Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Autotrophs and Heterotrophs Autotrophs are producers – Make food using energy from environment and carbon from inorganic molecules Heterotrophs are consumers – Obtain carbon from organic compounds assembled by other organisms Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Photosynthesis Sustains Life Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  First Stage of Photosynthesis: Light-Dependent Reactions First stage of photosynthesis (“photo”) Driven by light energy Conversion of light energy to the chemical bond energy of ATP Splits water (photolysis) to yield H+ and electrons to form NADPH; oxygen released Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Second Stage of Photosynthesis: Light- Independent Reactions Second stage of photosynthesis (“synthesis”) NADPH and ATP generated by light-dependent reactions drive synthesis of sugars from CO2 and H2O NADP+ and ADP recycled for use in the light- dependent reactions Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Coenzymes Connect the Reactions of Photosynthesis Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Where Photosynthesis Occurs Chloroplast – Thylakoid membrane ▪ Highly folded into stacks of interconnected thylakoids ▪ Light-dependent reactions – Stroma ▪ Cytoplasm-like fluid inside the chloroplast ▪ Light-independent reactions Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Site of Photosynthesis in a Leaf Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  6.2 Sunlight as an Energy Source 1882: Theodor Engelmann’s photosynthesis experiment – Directed a spectrum of light across individual strands of green algae; added motile, oxygen-requiring bacteria – Used oxygen emission as a measurement of photosynthetic activity – Clustering of bacteria near blue and red light indicated these wavelengths of light are optimal for driving photosynthesis Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Theodor Engelmann’s Photosynthesis Experiment Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Light is Electromagnetic Radiation Light – Electromagnetic radiation – Travels as waves, in energy packets (photons) – Wavelength (nm) = the distance between the crests of two successive waves – Photon’s energy is related to wavelength ▪ The shorter the wavelength, the higher the energy Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Visible Light Drives Photosynthesis Visible light – Main form of energy that drives photosynthesis – Small part of the spectrum of electromagnetic radiation (380 to 750 nm) – We perceive different wavelengths as different colors ▪ Light with all wavelengths combined appears white ▪ White light is separated by prisms Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Properties of Light Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  To Catch a Rainbow Photosynthesizers use pigments to capture light of specific wavelengths Chlorophyll a is the most common photosynthetic pigment – Absorbs violet, red, and orange light – Reflects green light (appears as green) Accessory pigments – Capture light of other wavelengths – Other functions (attract pollinators; antioxidants) Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Accessory Pigments The combination of photosynthetic pigments differs among species – Photosynthetic species are adapted to the environment in which they evolved – Light that reaches different environments varies in its proportions of wavelengths Green plants – Appear green due to abundant chlorophyll a – Disassembly of chlorophylls during autumn reveals accessory pigments Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Photosynthetic Pigments Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  6.3 Light-Dependent Reactions Light-harvesting complex in thylakoid membrane – Absorbs a photon; one of its electrons jumps to a higher energy level – Extra energy emitted as a photon as electron falls back to lower energy level – Photon passed back and forth between complexes – Photon becomes absorbed by a photosystem Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Photosynthetic Pigments in the Thylakoid Membrane Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Photosystem Large complex of molecules in thylakoid membrane Reaction center (proteins, pigments, and cofactors) surrounded by a ring of light-harvesting complexes Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Light-Dependent Reactions: Cyclic and Noncyclic Pathways Noncyclic pathways – Use photosystems I and II – Produce ATP, O2, and NADPH – Primary photosynthetic system Cyclic pathways – Use photosystem I only – Produce ATP – Evolved before noncyclic pathways Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Light-Dependent Reactions, Noncyclic Pathway Steps of the Noncyclic Pathway: Photosystem II 1) Photosystem II absorbs a photon, followed by loss of electrons 2) Photosystem II pulls electrons from water molecules to replace lost electrons – Photolysis: water is broken down to yield H+ and O2 3) Electrons enter an electron transfer chain in the thylakoid membrane 4) H+ gradient forms across the thylakoid membrane Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Steps of the Noncyclic Pathway: Photosystem I 5) After electrons move through first electron transport chain, they are accepted by photosystem I 6) Pair of chlorophylls in photosystem I releases electrons, which enter a second electron transfer chain; NADPH forms Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Steps of the Noncyclic Pathway: ATP Synthesis 7) Hydrogen ions in the thylakoid compartment are propelled through ATP synthases 8) ATP synthases phosphorylate ADP in the stroma to form ATP – Electron transfer phosphorylation ▪ Process by which electron flow through electron transfer chains drives ATP formation Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Light-Dependent Reactions, Noncyclic Pathway Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. chlorophyll Pancake = Thylakoid Membrane Syrup = the Stroma where sugar is made  Steps of the Cyclic Pathway 1) Photosystem I absorbs a photon and emits electrons 2) Electrons ejected from photosystem I enter an electron transfer chain 3) H+ gradient forms across thylakoid membrane to drive ATP formation 4) Electrons that reach the end of the electron transport chain return to photosystem I – NADPH and O2 do not form Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Light-Dependent Reactions, Cyclic Pathway Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Roles of the Cyclic and Noncyclic Pathways Noncyclic pathway – Has additional photosystem with access to unlimited supply of electrons from water – Electrons stored in NADPH are used to produce sugars from CO2 Cyclic pathway – Produces O2 but not NADPH – Not enough ATP is produced in the noncyclic pathway to balance NADPH, so cyclic pathway provides extra ATP Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  6.4 Light-Independent Reactions The Calvin–Benson cycle – Builds sugars in the stroma of chloroplasts – Not powered by light energy ▪ Driving force is ATP and NADPH formed by the light-dependent reactions – Uses carbon atoms from CO2 to make sugars ▪ Carbon fixation o Carbon from an inorganic source is incorporated into an organic molecule Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Steps of the Calvin–Benson Cycle 1) Rubisco fixes carbon by attaching CO2 to 5-carbon RuBP – The intermediate splits to form two 3-carbon PGA molecules per CO2 molecule – Six PGA total 2) Each PGA receives Pi from ATP, plus H+ and electrons from NADPH to form six PGAL 3) Five PGAL regenerate three RuBP 4) One PGAL is exported to the cytoplasm to combine with another PGAL to form sucrose Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. The Calvin–Benson Cycle in a Chloroplast Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Stomata Tiny, closable gaps on the surfaces of leaves and stems Open stomata – Allow CO2 to diffuse from the air into the plant cells – Allow O2 to diffuse out of these cells and into the air Closed stomata – Conserve water on hot, dry days – Limit the availability of CO2 for the light-independent reactions; sugar synthesis slows Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  C3 Plants Fix carbon only by the Calvin–Benson cycle Light-dependent and light-independent reactions run during the day When stomata are closed: – O2 levels rise and CO2 levels fall in plant tissues – Both gases are substrates of rubisco and compete for active site Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Photorespiration is Inefficient When O2 levels rise: – Rubisco attaches O2 to RuBP (photorespiration) to create substrate for Calvin–Benson cycle ▪ Intermediates must be transported among three organelles ▪ Requires ATP; produces CO2 and ammonia o CO2 is lost; ammonia must be detoxified Photorespiration is therefore inefficient – C3 plants compensate by making lots of rubisco Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Photorespiration Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  6.5 Carbon-Fixing Adaptations of Plants Some plants have evolved to minimize photorespiration – C4 and CAM plants Stomata are closed on hot, dry days Sugar production remains high Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Carbon-Fixing Adaptations of C4 Plants Fixes carbon twice in two cell types – Mesophyll cells – Bundle-sheath cells – This minimizes photorespiration by keeping CO2 levels high and O2 levels low near rubisco Examples – Corn, bamboo Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. C4 Plants Minimize Photorespiration Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Carbon Fixation in C4 Plants Fixes carbon 2x which uses more ATP but more efficient at making sugar Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.  Crabgrass, a C4 Plant Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Carbon-Fixing Adaptations of CAM Plants Conserve water even in desert regions with extremely high daytime temperatures Open stomata at night when lower temperatures minimize evaporative water loss Conserve water by fixing carbon twice, at different times of day Copyright © 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.