BIOLOGY 111 1st Edition Lecture 12 Outline of Last Lecture I Energy Flow II Cellular Respiration III Redox Reactions IV Pathways of Cellular Respiration V Cancer Cells VI Catabolism VII Feedback Inhibition Outline of Current Lecture I Photosynthesis II Photosynthesis in Plants III Light Reactions and Calvin Cycle IV Nature of Sunlight V Photosystems Current Lecture Photosynthesis Converts sunlight to chemical energy that is stored in sugar and other organic molecules The products of cellular respiration become the reactants for photosynthesis Electrons are stripped of the water molecule produced in cellular respiration and transferred to CO2 to reduce the carbon to a carbohydrate level This requires lots of energy Releases O2 as a byproduct Photosynthesis in Plants Occurs in the chloroplasts located mostly in the mesophyll cells of the leaves of plants Within the chloroplasts there are These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Thylakoids third membrane system that segregates the stroma from the thylakoid region within the thylakoid space Granum thylakoid sacs are stacked in columns The stroma fluid filled region between the thylakoid membrane and inner membrane Chlorophyll located in thylakoid membrane and they are what gives plants their green color Light Reactions and the Calvin cycle The thylakoid region is the site of light reactions inside the chloroplasts The photo part of photosynthesis Converts solar energy into chemical energy Light reactions use solar energy to make ATP and NADPH Water is split to provide electrons and protons and give of O2 as a byproduct This supplies chemical energy and reducing power to the Calvin cycle The Calvin cycle occurs in the stroma of chloroplasts The synthesis part of photosynthesis The calvin cycle incorporates CO2 into organic molecules carbon fixation and convert them into sugar Nature of Sunlight Light is an electromagnetic wave Electromagnetic waves are disturbances of electrical and magnetic fields not disturbances of the medium through which light travels Wavelength distance between the crests of electromagnetic waves High energy is associated with shorter wavelengths Low energy is associated with longer wavelengths Visible light is 380 750nm in wavelength Light is either absorbed transmitted or reflected When light is reflected off a surface we see that color i e green light is reflected back off of a plants leaves because the wavelengths associated with green are reflected Black light is all absorbed White is all reflected Photosystems A photosystem is composed of a reaction center complex surrounded by several lightharvesting complexes When a pigment molecule absorbs a photon the energy transferred from pigment molecule to pigment molecule in like a wave They each get pushed up to an excited state one at a time but then are each brought back down to their ground state passing their energy to excite the next one Inside the reaction center complex is a molecule capable of accepting electrons primary electron acceptor When this molecule gets excited the electron does not go back down to groundstate instead it is transferred from p680 down an electron transport chain to another primary acceptor p700 Each photoexcited electron passes from the primary electron acceptor of photosystem 2 to photosystem 1 photosystem 2 is before photosystem one because of the difference in times they were discovered and named