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Glycolysis, TCA, Gly

9/28/12 Directed study

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
Created by: 583931909