Exam 4 Review Chapter 10 1 Light is electromagnetic energy 10 31 2013 Light energy has both wavelike and particle like properties 1 Wave like properties o Electromagnetic energy travels in waves o Wavelength difference between crests of electromagnetic waves o Electromagnetic spectrum o gamma rays 10 3 nm to 103 m o radio waves o Visible light 380 nm to 750 nm 2 Particle like properties o Electromagnetic energy also travels in particles o Discrete particles called photons 2 Photosynthetic pigments The Light Receptors Substances that absorb light are known as pigments Different pigments absorb different wavelengths of light We see light that is reflected The absorption spectrum of a pigment can be measured using a spectrophotometer Carbon dioxide and oxygen enter and leave plants by way of the stomata Chlorophyll a is the pigment that participates in the light reaction Other pigments chlorophyll b and carotenoids are called accessory pigments Photo excitation and Electron Transfer 3 An electron in a chlorophyll molecule is boosted to an excited state from its ground state by the absorbed light energy photons The excited electron may be transferred to an electron carrier molecule or fall back to the ground state releasing its energy as Heat or light fluorescence The Light Reactions An Introduction 4 Convert solar energy to chemical energy Produce no sugar Occur in thylakoids Photophosphorylation Using chemiosmosis to power the addition of a phosphate group to ADP Noncyclic photophosphorylation 4 Photons H2O NADP H 4 ADP 4 Pi 2 680 2 700 2 O2 NADPH 4 ATP 4 H2O Electrons flow in a path from one electron carrier to the next Light excites electrons in PS II P680 Electrons transferred to the primary electron acceptor Electrons flow down the electron transport chain Electrons transferred to PS I P700 Light excites electrons in PS I P700 Electrons transferred to the primary electron acceptor Electrons transferred to NADP Electrons and reducing power are stored in NADPH The flow of electrons and the splitting of water also creates a proton gradient across the thylakoid membrane which then is used to synthesize ATP by chemiosmosis Cyclic photophosphorylation 2 Photons 700 2 ADP 2 Pi 2 ATP 2 H2O Only photosystem I is active Electrons flow in a path form one electron carrier to the next Light excites electrons in PS I P700 Electrons transferred to the primary electron acceptor Electrons flow down the electron transport chain Electrons transferred to PS I P700 Electrons from the electron transport chain replace electrons lost from PS I 5 The Calvin Cycle Occurs in the stroma 1 Starts with carbon fixation taking CO2 from the atmosphere and converting it into organic molecules 2 Adds electrons to reduce carbon to carbohydrates Powered by NADPH and ATP made in the light reactions 6 Comparing and contrasting Chemiosmosis Similarities Electron transport chains move protons across membrane as electron are moving down the chain ATP synthase is in the same membrane as the electron transport chain Diffusion of H is coupled to ATP production Many components are very similar in structure Differences 1 Electron transport chain Origin of electrons o in respiration they come from food via NADH o in photosynthesis they come from H2O or PS I Origin of energy o in respiration energy is chemical energy from food o in photosynthesis energy is light energy Chapter 12 1 The Cell Cycle Cell division Reproduction of cells Some characteristics of cell division o Replication of DNA o Equal distribution of DNA to opposite ends of the dividing cell o Separation into two daughter cells Genome A cell s endowment of DNA o DNA must be replicated then divided so that each new daughter cells will have a complete genome DNA molecules are packaged into structures called Chromosomes a threadlike structure of nucleic acids and protein found in the nucleus of most living cells carrying genetic information in the form of genes o DNA and proteins that make up a chromosome are called the chromatin Human cells all except for the sex cells have 46 chromosomes 23 from each parent cell Each duplicated chromosome has 2 sister chromatids which are joined copies of the original chromosome o Each sister chromatid has a centromere an area containing specific DNA sequences where the two chromatids are attached most closely Mitosis Cytokinesis The division of the genetic material in the nucleus The division of the cytoplasm 1 Interphase Cell grows and copies Interphase is the longest part of the cell cycle It takes up about 90 of cell division time G1 Grows S Chromosomes duplicated G2 Grows 2 M Phase M Phase consists of Mitosis and Cytokinesis Mitotic Spindle Begins to form during prophase Centrosome two centrioles a subcellular region containing the material that that functions throughout the cell to organize microtubules centrosome Kinetochore of DNA at each centromere Array of short microtubules extending from each Structure of proteins associated with specific sections Aster Prophase o Chromatin coils tightly condensing into chromosomes o The nucleoli disappears o Duplicated chromosome appears as two sister chromatids joined at their centromeres o Mitotic spindle begins to form Centrosomes and microtubules o Centrosomes move away from each other Prometaphase o Fragmented nuclear envelope o Microtubules of centrosomes invade nucleus o Sister chromatids now have kinetochore Some microtubules attach the kinetochores Metaphase o Centrosomes are now at opposite ends of the cell o Chromatids line up across cell o Microtubules are fully attached to the kinetochores of the centromeres of the chromatids and the centrioles Ready to pull sister chromatids apart o Shortest stage of mitosis o Sister chromatids separate and move to opposite ends of the Anaphase cell o The cell elongates Telophase o Two daughter nuclei form on each side of the cell o Nucleoli reappear o Chromosomes become less coiled o Microtubules are depolymerized o Mitosis is complete Cytokinesis o Cleavage furrow in animal cells pinches the cell in two o Two daughter cells appear as the cytoplasm splits Chapter 13 1 Meiosis In cellular respiration the electrons from sugar s carbon and hydrogen atoms lose potential energy oxidation as they are transferred toward oxygen In photosynthesis the electrons from water s hydrogen atoms and carbon dioxide s carbon atoms gain potential energy reduction as they are transferred toward sugar Carbon reduced in calvin cycle Light reactions reduce
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