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Glycolysis, TCA, Gly
9/28/12 Directed study
| Question | Answer |
|---|---|
| What does glycolysis do? | Cleaves and oxidizes glucose |
| What are the products of glycolysis? | pyruvate, ATP (small amount), and NADH |
| Where does glycolysis occur? | Cytosol of cell |
| Is glycolysis easily reversed? | No, it has an overall negative delta G |
| What is the reverse process of glycolysis? | Gluconeogenesis |
| Does gluconeogenesis require any input? | Yes, energy and special mechanisms to get around irreversible steps. |
| Is glycolysis an aerobic process? | No (required for production of energy from glucose either aerobically or anaerobically) |
| What process must be active for the synthesis of glycogen or fatty acids to take place? | glycolysis |
| What are required starting materials for glycolysis? | NAD+ and ADP |
| WHat facilitative transporters allow glucose to get into the cell? | GLUTs |
| Which cells have high affinity (low km) transporters highly expressed on the cell surface? | Red blood cells, brain tissue |
| What organ has low affinity glucose transporters? | liver |
| Which tissues have insulin-sensitive transporters? | Muscle and adipose |
| What are the characteristics of insulin transporters? | High affinity for glucose, but a small number present. They are transported in vesicles |
| How does "trapping" of glucose inside the cell occur? | Phosphorylation. Glucose 6 phosphate can't cross the membrane. |
| What enzyme catalyzes the reaction of Glucose to Glucose 6 phosphate? | Hexokinase |
| What are the characteristics of the brain isoform of hexokinase? | Low km for glucose, not regulated by insulin |
| What are the characteristics of the muscle isoform of hexokinase? | higher km for glucose, upregulated by insulin |
| What are the characteristics of the liver isoform of hexokinase? | Even higher kim, also upregulated by insulin |
| What is the liver isoform of hexokinase inhibited by? | Glucagon |
| What is the liver isoform of hexokinase called? | glucokinase |
| What are the three things glucose 6 phosphate can be used for? | glycolysis process, pentose phosphate pathway, glycogen |
| What is the glucose 6 phosphate isomerized to? | fructose 6 phosphate |
| What is fructose 6 phosphate phosphorylated to? | fructose 1,6 biphosphate |
| What is the enzyme that catalyzes this step? | phosphofructokinase-1 |
| What is the rate limiting enzyme in glycolysis? | phosphofructokinase-1 |
| What is the muscle isoform of PFK-1 activated by and inhibited by? | Activated by AMP, inhibited by ATP |
| What does fructose 1,6 biphosphate then split into? | dihydroxyacetone phosphate, glyceraldehyde 3 phosphate |
| Can DHAP and G3P be interconverted to one another? | Yes |
| What is the product of the final reversible reactions? | Phosphoenolpyruvate |
| What enzyme convertes phosphoenolpyruvate to pyruvate? | Pyruvate kinase |
| What tissue upregulates pyruvate kinase with insulin, and inhibits it with glucagon? | liver |
| What tissue does not regulate pyruvate kinase activity? | muscle |
| How does formation of NADH occur in glycolysis? | Reduction of NAD+ |
| What must occur before glycolysis to continue? | Oxidation of the NADH back to NAD+ |
| What are the two main ways of regenerating the NAD+? | Donation of an NADH electron to the electron transport change (oxidative phosphorylation), lactase dehydrogenase reaction (important for anaerobic tissues) |
| What must pyruvate be converted to to be used for aerobic ATP production? | acetyl CoA |
| What enzyme catalyzes the change from pyruvate to acetyl CoA? | pyruvate dehydrogenase |
| Where does this process occur and is it reversible? | mitochondria, no |
| What does pyruvate dehydrogenase control? | flow of pyruvate into the TCA cycle |
| What does the mechanism of regulation by pyruvate dehydrogenase complex involve? | phosphorylation/dephosphorylation of PDH |
| What is the PDH activated and inhibited by? | Activated by substrates, ADP, and calcium. Inhibited by products and ATP |
| What does exercising muscle cause? | Elevated calcium and ADP levels |
| What does elevated calcium and ADP levels encourage? | The production of acetyl CoA from pyruvate only if the tissue is well oxygenated. |
| What are the substrates and products of the TCA cycle? | Carbons from acetyl CoA are oxidized to produce CO2, NADH, FADH2 |
| What are the NADH and FADH2 reoxidized through oxidative phosphorylation to produce? | ATP |
| What is the TCA cycle required to generate ATP from? | ketones, fatty acids, alcohol, amino acids |
| What occurs in the first step of the TCA cycle? | Oxaloacetate condenses with acetyl CoA to form citrate |
| Is the oxaloacetate recycled? | Yes |
| What is the key rate limiting enzyme of the TCA cycle? | isocitrate deydrogenase |
| What is isocitrate dehydrogenase stimulated and inhibited by? | Stimulated by ADP and calcium, inhibited by NADH |
| What is the citrate intermediate used for? | Fatty acid synthesis |
| What is the succinyl CoA intermediate required for? | Synthesis of heme |
| What enzyme catalyzes the synthesis of oaloacetate from pyruvate? | pyruvate carboxylase |
| Can acetyl CoA cross the mitochondrial membrane? | No |
| What is acetyl CoA converted to so it can cross the mitochondrial membrane to the cytosol? | Citrate |
| What is the citrate in the cytosol converted into so it can be used to make fatty acids? | acetyl CoA |
| What is PFK-1 in the liver controlled by? | Inhibited by ATP and citrate, activated by AMP |
| Which enzyme in the liver can override the signal to shut down PFK-1 in the liver? | PFK-2 |
| What does PFK-2 do? | converts some of the fructose 6-phosphate formed in glycolysis to fructose 2,6 biphosphate |
| What is PFK-2 stimulated and inhibited by? | Stimulated by insulin, inhibited by glucagon |
| What are all three of the irreversible enzymes of glycolysis stimulated by? | insulin |
| What are they inhibited by? | Glucagon |
| What is the enzyme upregulated by insulin in muscle? | Hexokinase |
| Do muscle cells have glucagon receptors? | NO |
| What about the structure of glucagon makes it easily released? | Branched structure |
| What is added to the glucose 1-phosphate to activate the glucose? | UDP |
| What enzymes are used to build glycogen? | glycogen synthase, branching enzyme |
| What enzyme is the regulated step? | Glycogen synthase |
| What enzymes are used to breakdown glycogen? | Glycogen phosphorylase, debranching enzyme |
| Which enzyme is the regulated step? | Glycogen phosphorylase |
| What is glucose 6 phosphatase? | In the liver, allows glucose 6 phosphate to be converted back to glucose |
| Where does insulin signal through? | tyrosine kinase receptor |
| What does glucagon and epi signal through? | GPCRs |
| What is glycogen synthase stimulated and inhibited by? | Stimulated by insulin, inhibited by glucagon and epi |
| What is glycogen phosphorylase stimulated and inhibited by? | Stimulated by glucagon and epi, inhibited by insulin |
| Does muscle have glucagon receptors? | No |
| What is glycogen degradation in the muscle regulated by? | need for ATP and whether or not the muscle is exercising |
| What do slow twitch muscle fibers have a high capacity for? | Aerobic metabolism |
| Why do they have this capacity? | Lots of mitochondria and myoglobin |
| What is myoglobin? | Similar to hemoglobin, but only has one subunit and can only bind one oxygen. |
| Why are slow twitch muscles resistant to fatigue? | myoglobin can serve as an oxygen store |
| What are the characteristics of fast twitch fibers? | higher glycogen content, less myoglobin, fewer mitochondria |
| Which muscles will have a higher proportion of slow twitch fibers? | posture muscles psoas in back |
| What occurs in skeletal muscle during a more prolonged fast or when exposed to cortisol? | breakdown of skeletal muscle and amino acids to make glucose |
| What is one way energy in muscle cells is mobilized? | Storage of creatine phosphate |
| What is creatine? | A molecule that is synthesized in kidney, and process is completed in the liver. |
| How is creatine transported? | In the blood to skeletal and cardiac muscle cells |
| What happens once creatine gets inside the cell? | Reacts with ATP to form creatine phosphate |
| What is the previous reaction catalyzed by? | creatine kinase (creatine phosphokinase) |
| Is creatine phosphate stable? | NO. it can also undergo a nonenzymatic reaction in which it cycles to form creatine. |
| Can creatine be catabolized? | NO, it is excreted in the urine |
| What does myokinase do? | converts 2 ADP to 1 ATP and ! AMP in skeletal muscle cells |
| What is the primary way cells obtain energy at the onset of exercise? | anaerobic glycolosis |
| What does fuel usage during exercise depend on? | type of muscle fibers, length and intensity of exercise |
| What is the cycling of lactate that occurs between anaerobic tissues and the liver when anaerobic glycolysis and gluconeogenesis are occurring simultaneously called? | Cori Cycle |
| High AST can indicate liver damage? What can it also indicate? | damage to skeletal and cardiac muscle |
| What is the brain isoform of CK made of? | Two beta subunits |
| What is the skeletal muscle isoform of CK made of? | Two M subunits |
| What is that cardiac muscle isoform of CK made of? | one beta and one M subunit |
| What are some situations where you would see an elevated CK-MM level? | rhabdomyolysis, myositis, and trauma or crush injuries |
| What else will you see in elevated CK-MM cases? | elevated serum myoglobin levels |
| What are serum creatine levels and clearance rates typically used to monitor? | Kidney function |
| What is the amount of creatine produced dependent on? | muscle mass |
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