Carbohydrate 2

• Glycogen is a homopolymer of a-D-glucose with linkage a=1,4 and branching a-1,6 (at about every 8-10 residues) and is stored as granules in hepatocytes.
• Controlled breakdown of glycogen increases the amount of glucose that is available between meals.
• Glycogen is mobilized to maintain blood glucose levels in between meals.
• Glucose from glycogen can provide energy whenever the requirement is sudden, such as during strenuous activity.
• Liver glycogen is degraded for distribution to other organs through the blood and maintaining proper blood glucose levels.
• Muscle glycogen is degraded for its use in energy production.
• Glycogenesis is the process of storing excess glucose for use by the body at a later time.
• Glycogenolysis occurs when the body, which prefers glucose as an energy source, needs energy.
• Glycolysis is the process where glucose is broken down to produce energy.
• During glycogenolysis, glucose is released as Glc-1-P, which is already phosphorylated without consuming ATP and cannot leave the cell and go to the bloodstream.
• Glucose-1-P readily enters the glycolytic pathway once it’s converted to glucose-6-P by phosphoglucomutase.
• The action of glycogen phosphorylase continues until there are about 4 residues left from the branch point.
• Re-modelling of glycogen occurs near the branch point.
• A-1,6 glycosidic bond is cleaved by an a-1,6-glucosidase during de-branching, releasing glucose that is converted to glucose-6-P and can enter glycolysis.
• The Light Reactions - Z Scheme is linear, meaning both NADPH and ATP are produced.
• RuBisCO, or ribulose - 1,5 - bisphosphate carboxylase - oxygenase, is the most abundant enzyme on earth and requires Mg 2+ as co-factor.
• Light Reactions of Photosynthesis involve the excitation of electrons in photosystems, which involves electron transfer from two photosystems: PS II to PS I.
• The reduction of 3 - PGA to GAP is the second step in the Calvin Cycle.
• Excitation of electrons in Photosystem II involves a series of excitations and energy transfer until it reaches the reaction center, where an excited electron is captured by the primary acceptor (pheophytin).
• The Calvin - Benzon Cycle or C 3 Photosynthesis involves the reduction of carbon from CO2 in a more reduced state as hexose, using NADPH and ATP produced from light reactions.
• The first step in the Calvin Cycle is the fixation of CO2 with ribulose - 1,5 - bisphosphate (RubP) to form 2 molecules of 3 - phosphoglycerate (3 - PGA), catalyzed by RuBisCO.
• Dark Reactions (Light Independent Reactions) involve the reduction of CO2 to form sugars using ATP and NADPH, and occur in the stroma.
• Cyclic Electron Flow occurs when NADP + is not available, where electrons from ferredoxin are transferred back to the Electron Transport Chain between Photosystem II and Photosystem I, resulting in only ATP being generated.
• In Photosystem I, plastocyanin transfers electrons to P700, where the excited electron is transferred to ferredoxin then to NADP + reductase, which uses high energy electrons to reduce NADP + to NADPH.
• Dark reactions of Photosynthesis occur in the stroma of the chloroplast, and light is still needed for activation of some involved enzymes.
• The Electron Transport Chain (ETC) consists of plastoquinone, cytochrome complex, and plastocyanin, and generates a proton gradient that drives ATP synthesis.
• Glucose-1-P is dephosphorylated in the liver and free glucose exits the hepatic cells and goes into the blood stream for maintaining proper blood glucose levels and transport to other organs (brain and muscles).
• Glucose-1-P is present in the muscle cells, which degrade glycogen for its own need.
• UDP-Glucose is the activated form of glucose that serves as glucose donor for glycogen synthesis.
• Photosynthesis is the process by which autotrophic organisms convert CO2 into sugars, with the use of energy coming from sunlight, involving the conversion of light energy into chemical energy.
• Glc - 6 - P to Glucose Overall Reaction: 2 pyruvate + 4 ATP + 2 GTP + 2 NADH, H + + 6 H 2 O → Glucose + 4 ADP + 2 GDP + 6 P i + 2 NAD +
• Alcohol Metabolism involves the steps: NADH promoting the reduction of oxaloacetate back to malate, no OAA becoming available for gluconeogenesis, and high [NADH] inhibiting fatty acid oxidation.
• The effect of Ethanol Metabolism is to inhibit TCA cycle by high [NADH], which in turn inhibits isocitrate dehydrogenase and alpha - ketoglutarate dehydrogenase, preventing the processing of acetyl CoA2.
• There are two phases of photosynthesis: Light Reactions and Calvin Cycle.
• During strenuous exercise, ATP requirement shoots up that cellular respiration cannot cope up, oxygen supply in the muscle becomes depleted, ETC and Krebs cycle stops, and conditions become anaerobic, leading to pyruvate being diverted for lactate production.
• Light Reactions involve the conversion of light energy to chemical energy, the production of ATP and NADPH, and occur in the thylakoid.
• Chloroplasts are the site of photosynthesis, containing pigments such as chlorophyll a, chlorophyll b, and carotenoids, which are excellent light harvesters due to the presence of conjugated double bonds.
• Lactate accumulation in the muscle is later on suppressed by the Cori Cycle.
• Gluconeogenesis and Hypoglycemia are inhibited when alcohol is metabolized, glycogen reserves are depleted, and blood glucose levels are significantly low, leading to hypoglycemia.
• Alcohol consumption leads to the accumulation of acetaldehyde in the liver, which reacts with functional groups of proteins, impairing liver function.