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23 Cards in this Set
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1. Describe the distinguishing characteristics of carbohydrates, and explain the biologically important function of this group.
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1. Carbohydrates are organic molecules that contain large amounts of chemical potential energy. Mainly they are energy storage. Through photosynthesis, they are created and is used by human cells for cellular respiration. Carbohydrates have less energy than lipids and fats. Mainly used in cellular respiration the carbohydrate Glucose. The formula for Glucose would be C6H12O6, and is broken down, in order to create ATP.
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2. What are the structural differences between monosaccharide, disaccharide, polysaccharide, glucose, starch, glycogen, and cellulose? Be sure to give an example for mono, di, and polysaccharides. Explain the biological importance of each of these molecules.
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2. A monosaccharide generally has some multiple of the unit CH2O such as glucose C6H12O6, while a disaccharide consists of two monosaccharides joined by glycosidic linkage (a covalent bond formed between two monosaccharides by a dehydration reaction) such as maltose, which is an ingredient to brew beer. A polysaccharide on the other hand are macromolecules, polymers with a few hundred to a few thousand monosaccharides, they serve as either storage material or building material for structures that protect the cell or the whole organism. An example of a storage polysaccharide would be starch, a polymer consisting of entirely of glucose monomers. Glycogen is a polymer of glucose and is also a storage polysaccharide. A structural polysaccharide is cellulose and is a major component of the tough walls that enclose plant cells and is a polymer of glucose. Although both cellulose and glucose have glycosidic linkages, the linkages differ. In starch, all the glucose monomers are in the alpha configuration, while for
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3. Explain how hydrolysis & dehydration synthesis relate to the various carbohydrates in the previous question.
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3. Disaccharide is formed from two monosaccharides joined by dehydration synthesis while a polysaccharide is formed from over a thousand monosaccharides all through dehydration reactions. The hydrolysis of glycogen in liver and muscle cells of animals causes them to release glucose when the demand for sugar increases. It is difficult for many organisms to hydrolyze cellulose, with only a few such as cows having the enzymes that can hydrolyze it for nutrients. Starch is made up of glucose monomers that are joined by 1-4 linkages, (number 1 carbon to number 4 carbon) which are formed through dehydration synthesis.
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4. Define oxidation and reduction. Explain how redox reaction are involved in energy exchanges. Explain the role of REDOX reactions in cellular respiration? Explain the role of REDOX reactions in photosynthesis.
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4. Oxidation is the loss of electrons, or the increase in oxidation state by a molecule. Reduction is the gain of electrons, or a decrease in oxidation by a molecule. Electrons contains the energy inside the molecules. Mostly, cellular respiration depend on the reduction of NAD+ to NADH and the oxidation of NADH to NAD+. The NADH are then used to fuel the proton pump and create a concentration gradient in the intermembrane space. In photosynthesis the oxidation of CO2 to glucose happens. Basically it’s a cycle, in which cellular respiration oxidizes glucose to CO2 and oxygen to water, and photosynthesis oxidizes CO2 to glucose and water to oxygen.
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5. Distinguish between substrate-level phosphorylation and oxidative phosphorylation. Give examples in photosynthesis and cellular respiration of both types.
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5. In oxidative phosphorylation it is the production of ATP using energy derived from the redox reactions of an electron transport chain, while substrate-level phosphorylation is the formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism. The citric acid cycle is an example from cellular respiration and the calvin cycle is an example for photosynthesis.
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6. Describe where cell respiration (glycolysis, fermentation, Kreb’s cycle, and electron transport) occurs in the cell. List the reactants required for each. Include which of the steps of cell respiration are part of the anaerobic & aerobic respiration pathway.
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6. The first step in cellular respiration is glycolysis, which occurs in the cytosol, where glucose is split into two molecules of pyruvate and is a part of the aerobic respiration pathway. The second step is the citric acid cycle or Krebs cycle where it takes place in the mitochondrial matrix and completes the breakdown of glucose by oxidizing a derivative of pyruvate to carbon dioxide. The electron transport chain is a collection of molecules embedded in the inner membrane of the mitochondrion. NAD+ removes electrons from food in the electron transport chain, with the electron then traveling across electron carriers until it ends up at oxygen. Fermentation is an extension of glycolysis that can generate ATP solely by substrate-level phosphorylation as long as there is a sufficient supply of NAD+ to accept electrons during the oxidation step of glycolysis. Since it is an extension of glycolysis, fermentation also occurs in the cytosol and is a part of the anaerobic respiration pathway.
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7. Define glycolysis and include the products that are produced. Explain why ATP is required at the beginning of glycolysis.
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7. Glycolysis is the metabolic breakdown of sugars and forms Pgal. Pgal contains 3C and since glucose has 6C it creates 2 Pgal. Pgal when it enters the mitochondria, then forms Pyruvate and NADH. The Pyruvate then forms Acetyal CoA, and CO2 and is put through the Krebs cycle, which forms 1 ATP, 3 NADH, and 1 FADH2. Then the NADH and FADH2 travels to the electron transport system and creates a concentration gradient by pumping out the H+ ions to the intermembrane space. Then oxidation phoshorylation takes place and with the gradient the H+ ion basically turns a turbine, which creates ATP. Glycolysis needs 2 ATP at first to get from the cytoplasm to the matrix of the mitochondria and the enzymes in the glycolysis pathways need energy to function and in the end you get Pyruvate.
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8. If no oxygen is present in the cell, why must glycolysis continue to either lactic acid formation or alcoholic fermentation?
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8. When there is no oxygen present, glycolysis must continue to alcohol fermentation to convert pyruvate to ethanol in two steps, the first being that it releases carbon dioxide from the pyruvate which is then converted to acetaldehyde, the acetaldyhyde is reduced by NADH to ethanol. This process regenerates the supply of NAD+ which is needed for the continuation of glycolysis. If needed glycolysis might also turn to lactic acid fermentation in which pyruvate is reduced directly by NADH to form lactate as an end product with no release of CO2, the human muscle cells make ATP by lactic acid fermentation when oxygen is scarce.
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9. Describe the reactions of Kreb’s cycle using roles of acetyl CoA, citric acid, NAD+, and FAD+. Include the products that are produced in Kreb’s cycle.
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9. In Krebs cycle, acetyl CoA is created from pyruvate where it joins with oxaloacetate to create citric acid. The citrate loses a CO2 molecule and the resulting compound is oxidized, reducing NAD+ to NADH, and this process repeats a second time for the compound, reducing NAD+ to NADH. Coenzyme A then attaches to the remaining molecule where CoA is displaced by a phosphate group, which is then transferred to GDP, forming GTP, and then to ADP, forming ATP. Two hydrogens are transferred to FAD from the resulting compound, forming FADH2. The addition of water rearranges bonds in the substrate and it is then oxidized, reducing NAD+ to NADH and regenerates oxaloacetate, repeating the cycle again.
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10. What is the importance of electron transport seen in the cristae membranes of the mitochondria?
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10. The electron transport is important because it creates the most ATP overall. It uses NADHs and FADHs with the electrons to pump out H+ ions out into the intermembrane space. By pumping out the H+ ions, it creates a concentration gradient outside the mitochondria. Oxidation Phosphorylation then takes place and basically, like a turbine the H+ ions flow back into the mitochondria, spins it and generates about 22 ATP net, which is the most out of the entire cycle.
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11. Describe the process of chemiosmosis. Explain how the exergonic slide of electrons down the electron transport chain is coupled to the production of ATP by chemiosmosis using the roles of NADH, FADH2, cytochromes, oxygen, and ATP synthase.
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11. NADHs and FADH2 carry elections from food during glycolysis and the citric acid cycle to an electron transport chain built into the inner mitochondrial membrane. The cytochromes move rapidly along the membrane, ferrying electrons between the large complexes. Chemical energy originally harvested from food is transformed into a proton-motive force, a gradient of H+ across the membrace. The hydrogen ions flow back down their gradient through a channel in an ATP synthase. The ATP synthase harnesses the proton-motive force to phosphorylate ADP, forming ATP. The use of an H+ gradient to transfer energy from redox reactions to cellular work is called chemiosmosis. Together, electron transport and chemiosmosis compose oxidative phosphorylation.
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12. Explain how membrane structure of the mitochondria is related to the membrane function in chemiosmosis
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12. Chemiosmosis involves the pumping of protons through special channels in the membranes of mitochondria from the inner to the outer compartment. The pumping establishes a proton gradient. After the gradient is established, protons pass down the gradient through particles designated F1. In these particles, the energy of the protons generates ATP, using ADP and phosphate ions as the starting points.
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13. Summarize the net ATP yield from the oxidation of a glucose molecule in both anaerobic and aerobic respiration.
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13. Glycolysis uses 2 ATP, but makes 4 ATP, which becomes 2 from the substrate-level and 2 NADH. The Transition Reach makes 2 NADH. The Citric Acid cycle makes 1 ATP, 3 NADHs, and 2 FADH2s in one turn. The Citric Acid cycle makes two turns per glucose molecule though, so 2 ATP, 6 NADHs, and 2 FADH2s are created. In total you’ve created a total of 10 NADHs and 2 FADH2s, which build the concentration gradient, through the electron transport chain, and through oxidative phospohorylation, each NADH makes 3 ATP, so 30 ATP from NADH, and each FADH2s makes 2 ATP, so 4 ATP. Adding it all together you get a net total of 38 ATP going through everything.
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14. Describe the structure of the leaf. Explain how the structure of the leaf helps the plant to do photosynthesis. Include an explanation of how the leaf responds to different environmental conditions, such as high heat and high wind and how this response affects photosynthesis.
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14. The mesophyll on the leaf is the inner tissue, while the stomata or guard cells are located on the bottom of the leaf. The surface of the tissue is called the cuticle, usually smooth so that photosynthesis can be maximized. When there is too much wind or heat, the stomata or guard cells tend to close up to prevent evaporation or excessive intake of CO2
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15. Describe the structure of the chloroplast. Include where each stage of photosynthesis occurs. Explain how the structure of the chloroplast relates to its function.
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15. Chlorophyll is the green pigment located within chloroplasts that absorbs light energy that drives the synthesis of organic molecules in the chloroplast. An envelope of two membranes encloses the stroma, the dense fluid within the chloroplast. Also, an elaborate system of interconnected membranous sacs called thylakoids segregates the stroma from another compartment, the interior of the thylakoids, or thylakoid space. This is where the light reactions as in the thylakoids, molecules of NADP+ and ADP pick up electrong and phosphate, respectively, and then are released to the stroma where the Calvin cycle occurs. The high energy cargo of NADP+ and ADP are transferred to the Calvin cycle to fuel its cycle.
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16. Write a summary equation for photosynthesis and compare to cell respiration.
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16. Photosynthesis: 6 CO2 + 6 H2O + sunlight → C6H12O6 + 6 O2
Cellular Respiration: C6H12O6 +6 O2 → 6 H20 + 6CO2 + 38 ATP Photosysnthesis equation uses sunlight and build glucose and creates oxygen using water and carbon dioxide. Cellular respiration breaks down Glucose and oxygen, into water and carbon dioxide, creating 38 ATP in the process. Basically these two equations are inverses and create a cycle in which, photosynthesis creates the fuel to drive cellular respiration and vice versa for cellular respiration for photosynthesis. |
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17. Describe the role of water, light energy, pigments, and NADP+ in the light dependent stage. Be sure to identify the major reactants and products of the light dependent stage.
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17. Light absorbed by chlorophyll drives a transfer of electrons and hydrogen from water to an acceptor called NADP+, which temporarily stores the energized electrons. Water is split in the process, and thus it is the light reactions of photosynthesis that give off O2 as a by-product. The major reactants are NADP+ and water, and the major product is O2.
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18. Describe the relationship between wavelengths of light and energy. Describe what an absorption spectrum and an active spectrum is. What wavelengths of light are most effective for photosynthesis? Explain why not all wavelengths are equally effective in plants.
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18. The wavelength of light is the distance between the crests of the waves, such as the electromagnetic spectrum. Photons are the particles of light that have a fixed quantity of energy which is determined by the wavelength of the light, the shorter the wavelength, the greater the energy. The absorption spectrum is the range of a pigment’s ability to absorb various wavelengths of light while the active spectrum is a graph that depicts the relative effectiveness of different wavelengths of radiation in driving a particular process. The wavelengths of light that work best for photosynthesis are around 420 nm and 680 nm. Not all wavelengths are equally effective because only certain wavelengths are mostly or fully absorbed by the pigment.
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19. Explain what happens when chlorophyll or accessory pigments absorb photons of light. Then trace electron flow through Photosystems II and I. Be sure to compare cyclic and noncylic electron flow.
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19. When chlorophyll or an accessory pigment absorbs photons of light, electrons get excited and the electrons get energized. The electrons then get transferred to the primary electron acceptors and so on and so forth.
When the electron reaches photosystem I, it fills the electron deficit of the reaction-center chlorophyll of photosystem I. The deficit is due to photo-excitation of electrons which are again trapped in an electron acceptor molecule, this time that of photosystem I. ATP is generated when the ATP synthetase transports the protons present in the lumen to the stroma, through the membrane. The electrons may either continue to go through cyclic electron transport around PS I, or pass, via ferredoxin, to the enzyme NADP+ reductase. Electrons and hydrogen ions are added to NADP+ to form NADPH. This reducing agent is transported to the Calvin cycle to react with glycerate 3-phosphate, along with ATP to form glyceraldehyde 3-phosphate, the basic building block from which plants can make a variety of su |
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20. Describe differences between chemiosmosis occurring in the mitochondria with photophosphorylation in the chloroplast.
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20. In mitochondria, the high–energy electrons dropped down the transport chain are extracted from organic molecules in chemiosmosis. Chloroplasts do not need molecules from food to make ATP; their photosystems capture light energy and use it to drive electrons to the top of the transport chain. In other words, mitochondria transfer chemical energy from food molecules to ATP (and NADH), whereas chloroplasts transform light energy into chemical energy in ATP (and NADPH).
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21. Describe the role of carbon dioxide, ATP, and NADPH in the Calvin cycle. Be sure to identify the major reactants and products of the Calvin cycle. Is light required to run the Calvin cycle? If not, explain why it doesn’t occur during the night.
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21. In the Calvin cycle, carbon dioxide is turned into glyceraldehyde-3-phosphate (G3P) and for the net synthesis of one molecule of it, the cycle must take place three times, fixing three molecules of CO2. Carbon dioxide enters the Calvin cycle and is attached to a five-carbon sugar named ribulose biphosphate (RuBP) where it is catalyzed by rubisco, with the product of the reaction being a six-carbon intermediate that splits in half into two molecules of 3-phosphoglycerate because it is so unstable (for each CO2). Each molecule of 3-phosphoglycerate receives and additional phosphate group from ATP, being 1,3-bisphosphoglycerate. Next, a pair of electrons donated from NADPH reduces 1,3-bisphosphoglycerate to G3P. For every three molecules of CO2 there are six molecules of G3P, one of which exits the cycle to be used by the plant cell, with the other five being recycled to regenerate the three molecules of RuBP. In order to do this, the cycle spends three more molecules of ATP, and the RuBP is now prepared t
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22. Describe what happens to rubisco when the oxygen concentration is much higher than carbon dioxide. What is the major consequence of photorespiration?
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22. Rubisco fixes on oxygen rather than carbon dioxide, and you can no longer have 2 molecules of PGA. The total number of carbon atoms would be five, instead of six. The other two carbons after the PGA, forms RuBP and goes to glycolate. This releases more carbon dioxide instead of oxygen. Since carbon dioxide is form and this occurs using light, it’s called photo respirations. Photorespiration is bad because it reduces the rate at which oxygen is created by one half. With less oxygen going around, it’ll be harder for our cellular respiration to occur. Also, it lowers the effectiveness of photosynthesis and reduces the total energy and glucose created by photosynthesis.
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23. Describe two important photosynthetic adaptations that minimize photorespiration.
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23. C4 photosynthesis and CAM. For C4 photosynthesis the Calvin cycle is confined to the chloroplasts of the bundle sheath. However, the cycle is preceded by incorporation of CO2 into organic compounds in the mesophyll. The first step, carried out by the enzyme PEP carboxylase, is the addition of CO2 to phosphoenolpyruvate (PEP), forming the four–carbon product oxaloacetate. PEP carboxylase has a much higher affinity for CO2 than rubisco and no affinity for O2. Therefore, PEP carboxylase can fix carbon efficiently when rubisco cannot—that is, when it is hot and dry and stomata are partially closed, causing CO2 concentration in the leaf to fall and O2 concentration to rise. After the C4 plant fixes carbon from CO2, the mesophyll cells export their four–carbon products to bundle–sheath cells through plasmodesmata. Within the bundle–sheath cells, the four–carbon compounds release CO2, which is reassimilated into organic material by rubisco and the Calvin cycle. Pyruvate is also regenerated for conve
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