Biosc 0150 Foundations of Biology I Review chapters 10 11 12 Review chapter 10 Photosynthesis 1 How would you describe photosynthesis in general terms to a non biologist The use of sunlight to manufacture sugars State a general description of photosynthesis in biological terms Transformation of light energy into chemical energy in carbohydrates a make all of their own food from ions and simple molecules Give three examples Autotrophs plants cyanobacteria green algae b have to obtain sugars and many other macromolecules from other organisms Give three examples Heterotrophs fungi animals bacteria c Balance the equation for photosynthesis CO2 H2O light energy C6H12O6 O2 H2O 6 CO2 12 H2O light energy 1 C6H12O6 6 O2 6 H2O d Photosynthesis is an endergonic exergonic suite of reactions that reduces to Cellular respiration is an endergonic exergonic suite of reactions that oxidizes to and results in the production of Endergonic CO2 glucose exergonic glucose CO2 ATP e What is source of O2 produced during photosynthesis H2O 2 List the three main things that can happen to electrons when light hits chlorophyll The electrons can drop back to a lower energy state causing fluorescence excite an electron in a nearby pigment to induce resonance or be transferred to an electron acceptor in a redox reaction a Describe the phenomena fluorescence If an excited electron falls back to its ground state some of the absorbed energy is released as heat and light This results in color that we can see b What does it mean for an electron to be in a higher energy state when it is excited The electron is elevated to an energy level above the ground state This means that the electron has moved up an orbital so suppose you had Hydrogen it would be kicked up to 2s or 6p c Explain the process of resonance the moment light hits chlorophyll Light hits chlorophyll the energy is absorbed and an electron is excited to a higher energy state The energy not the electron is passed to nearby chlorophyll which sets a chain reaction for the same thing happening until the energy reaches the reaction center where the excited electron s energy is permanently transformed from electromagnetic energy to chemical energy d What is the significance of having a lot of chlorophyll surrounding a reaction center More chlorophyll equates to more opportunities for electrons to become excited and have their energy passed to reaction centers This allows for a more efficient transformation of electromagnetic energy to chemical energy 3 What are the two linked sets of reactions of photosynthesis The light capturing reaction and the Calvin Cycle a Which reaction is dependent on the other Explain The Calvin cycle requires the products ATP and NADPH of the light capturing reactions b What are the products of each set of reactions The products of the light dependent reaction are ATP NADPH and O2 the products of the Calvin Cycle is 3 carbon sugar G3P Adel Anthony Kathleen Megan Dr Swigonova Page 1 of 18 Biosc 0150 Foundations of Biology I Review chapters 10 11 12 c How are the two sets of reactions linked to one another The reactions are linked by electron carrier NADPH transporting electrons released by H2O splitting to reaction center of photosystem II 4 Where does photosynthesis take place in a cell Chloroplasts a Name the components of this organelle and how they relate to one another Use the following terms thylakoids grana stroma The interior of a chloroplast in dominated by thylakoids which often occur in stacks called grana The space inside the thlyakoid is its lumen The fluid filled space between the thylakoids and the inner membrane is the stroma b True or False Pigments have colors because we see the wavelengths they absorb FALSE They have colors because we see the wavelengths they do not absorb c The most common pigment to absorb photon s energy in chloroplasts is chlorophyll whose function is d Additional but less common pigments include a class of compounds called carotenoids What is their function These are accessory pigments that absorb light in ranges complimentary to chlorophyll Carotenoids absorb in the blue and green parts of visible spectrum widening the action spectrum for photosynthesis They also play a protective role quenching free radicals by accepting or stabilizing unpaired electrons 5 What is the first molecule that reacts with CO2 in the Calvin cycle How many carbon atoms does this molecule contain What is the product of this reaction RuBP 5 two molecules of 3 phosphoglycerate 3PG a In the second step of the calvin cycle 3 phosphoglycerate 3PG is phosphorylated by ATP and reduced by NADPH to form which molecule Does this molecule have more or less energy than 3PG Glyceraldehyde 3 phosphate G3P it has much more energy b What is the fate of the majority of the glyceraldehyde 3 phosphate G3P that is generated in the second step of the Calvin cycle It is used to regenerate RuBP c For every 6 molecules of G3P that are produced how many go toward production of sugars One 6 Explain why photorespiration occurs in competition with carbon fixation You should mention the affinity of rubisco to CO2 and O2 Rubisco is an enzyme which catalyzes the addition of both carbon dioxide and oxygen to RuBP Ideally you would only want carbon dioxide to be fixed to RuBP so this intermediate could be used in the Calvin cycle In some cases oxygen is fixed to RuBP by rubisco leading to photorespiration Photorespiration undoes photosynthesis by producing intermediates which consume ATP and release carbon dioxide 7 True or false If false correct the statement a Plants have mitochondria and use cellular respiration to produce ATP True b C4 plants increase efficiency of photosynthesis by separating reactions in time e g using fixed carbon sources during the day while stomata are closed False CAM plants do this Adel Anthony Kathleen Megan Dr Swigonova Page 2 of 18 Biosc 0150 Foundations of Biology I Review chapters 10 11 12 c Sucrose is produced from glucose and fructose mainly when photosynthesis is occurring at a high rate Otherwise starch is produced for energy storage False Sucrose is produced when photosynthesis is occurring at a slow rate This is the time when a plant needs to obtain energy without depleting all of its stored starch 8 What do plants contain that allow them to absorb electromagnetic radiation They have chlorophylls and carotenoids a Chlorophylls absorb energy in the blue and red regions of the visible spectrum while carotenoids