AZDI biochem quiz 2 Flashcards

Question

How id glycolysis regulated in muscles?

Answer 1

* Remember that hte goal sis to generate ATP during activity * ATP levels regualte glycolysis * a high ratio of ATP/AMP while rest prevents Pyruvate kinase from converting PEP to pyruvate and F6P from becoming F1,6-BP * While during excercise, the demand for ATP is high and thus decreasing the the rate of ATP to AMP and releasing the inhibtory control of pyruvate kianse

Answer 2

* Goal: to maintain blood glucose levels * to provide building blocks for other pathways (in resposne to biochemical diversity and need) * Phosphofructokinase * Activated by F-2,6- BP * Inhibtited by citrate * Glucokinase * no Hexokinase in liver * Glucokinase is not inhibited by glucose 6-phosphate- glucose permanently trapped * Pyruvate Kinase is regulated by allosteric effectors and covalent modification

Answer 3

* Glucokinase * activty and blood glucose * low = inhibition and dont want to trap glucose

Answer 4

* fructose (like high cructose corn syrup) * linked to fatty liver insulin insensitivity, obesity, and ttype 2 diabetes * THese disorders not result of simple excess energy consumption but rather how fructose is processde by the iver * actions of fructokinase and triose kinase bypass the most important regulatory step in glycolysis, the phosphofrutokinase-cataylzed reactions * fructose dervied G3P and DHAP are processed by glycolysis to pyruvate and acetyl CoA in an unregulated Fashion * Excess acetyl CoA converted to Fatty acids, which can be transported to adipose tissue to form triacylglycerols resulting in obesity * Liver also begins to accumulate fatty acid, resulting in fatty liver * activity of the fructokinase and triose kinse can deplete the liver of ATP and inorganic phosphate, comprising liver functions

Answer 5

INability to metabolize lactose Drinking milk causes disturbances in GI functions caused by deficiency in enzyme lactase (which breaks down lactose to glucose and glactose)

Answer 6

* Disruption of galactose metabolism is called _galactosemis_ * classic galactosemia (most common form) is an inheirted deficiency in galctose 1-phosphate uridyl transferase activity * symptoms * Vomiting/ diarrrhea after consuming milk * enlargemnt of liver and jaundice, sometimes progressing o cirrhosis * cataracts in eyes * lethargy and retarded mental development * significant elevation of blood falactose levels, and presence of galactose in urine * Diagnostic criteron : absence of the transferase in RBC * Treatment: remove galactose (and lactose ) from diet * Although elimination of glactose from diet prevents liver disease and cataracts development, majority of patients still suffer from central nervous system malfunction most commonly a delayed acqusition of language skills

Answer 7

* Cataracts is the clouding of the normally clear lens of the eye. If the transferase is not active in the lens of the eye, the presence of aldose reductase causes the accumulation galactose to be reduced galactitol

Answer 8

* Tumors display enhance rates of glucose uptake and glycolysis * rapidly growing tumor cells metabolize glucose to alctate even in the presence of oxygen, a process called **aerobic glycolysis** or the **warburg effect** * tumors with a high glucose uptake are particularly aggressive, and the cancer is likely to have poor prognosis * visualization of tumor and effectiveness of treatment: * A nonmetabolizable glucose analog, 2-18F-2-D-deoxyglucose, detected by a combination of **positron emission tomographu (PET\_ and computer aidsed tomogrpahy (CAT)**

Answer 9

PHOSPHOFRUCTOKINASE

Answer 10

GLUCOSE 1-PHOSPHATE

Answer 11

* occurs in liver and kidney * synthesis of glucose from non-carbohdrate precursors * pathway not a reversal of glycolysis * Pathway converts pyruvate into glucose * No ATP made. It is only comsumed * Major precursors are lactate, amino acids, and glycerol

Answer 12

* pyruvate carvoxylase * Phosphoenolpyruvate carboxykinase * fructose 1,6-bisphosphatase * Glucose 6-phosphatase

Answer 13

* PC is a mitochondrial enzyme * other enzymes of gluconeogenesis found in cytoplasm * OAA (product of PC) transported to cytoplasm via malate suttle

Answer 14

* Enzyme located in the lumen of the endoplasmic reticulum * T1 = transports glucose 6-phosphate to ER * T2 = transports inorganic phosphate back into cytosol * T3 = transports glucose back into cytoplasm

Answer 15

* Glycolysis generates ATP * Gluconeogenesis consumes ATP * Energy charge (ATP/ADP ratio) which pathway will be most active * Gluconeogenesis and glycolysis are reciprocally regulated

Answer 16

* in the liver, rates of glycolysis and glucogenesis are adjusted to maintain blood glucose * fructose 2, 6- nisphosphate strongly **stimulates phosphofructokinase** and *inhibits fructose 1, 6-bisphosphatase* * Two enyzmes regulate the oncetration of fructose 2,6 bisphosphate: phosphofructolinase 2 (PFK2) and fructose bisphosphatase 2 (FBPase2) insulin inhibts FBPase2 and stimulates PFK2 while glucagon does the opposite

Answer 17

Lactate produced in skeletal muscle and RBC can be converted back to pyruvate in the liver THe pyruvate can enter the gluconeogenic pathway and regenerate glucose (which was the source of lactate)

Answer 18

Oxaloacetate

Answer 19

FRuctose 1,6 Bisphosphatase

Answer 20

* Glycogen is a long chain homopolymer of glucose molecule with branches * Glucose molecules within chain **linked** via **alpha-1,4, glycosidic bonds** * **Branch points** formed via **alpha 1,6 glycosidic bonds** between glucose monomers of seperate chains * **non-reducing ends** each contain a terminal glucose with a free hydroxyl group at carbon 4 * reducing end consists of glucose monomer connected to a protein called **glycogenin** * ***Glycogenin*** creates a short glycogen polymer on it self and serves as a primer for glycogen synthesis * gylcogen is degraded and extended for non reducing end

Answer 21

* glycogen storage in liver, muscle, and other tissues * Stored as **granules** * Granules contain not only **glycogen** but also the enzymes needed for **glycogen metabolism** * defects in these enzymes can lead to disorders

Answer 22

Liver glycogen = regualtes bood glucose levels muscle glycogen = provides reservoir of fuel (glucose) for physical activity

Answer 23

* Regulated storage and release of glucose * synthesis and degradation of glyogen involve different pathways * glycogenesis = glucogen synthesis * Glycogenolysis = glycogen degradation * both pathways regulated independently * regulation * Allosteric control * covalent modification through reversible phosphorylation of key enzymes * Hormonal control

Answer 24

Glycogen synthesis

Answer 25

trapping and activation of glucose * glucoskinase / hexakinase * in cytosol of hepatocytes and muscle cells catalyze phosphorylation of glucose to glucose 6 phosphate * TRAPS the GLUCOSE IN CELL * Phosphoglucomutase then reversible isomerizes glucose-6-phosphate to glucose -1-phosphate * URdine diphosphate (UDP)- glucose pyrophosporylase then transfers the glcose 1 phosphate to uridine tri-phospjate (UTP) which generates UDP-glucose (active form of glucose ) * Breakdown of pyrophosphosphate to Pi generates energy

Answer 26

Catalyzed by UDP-glucose pyrophosphorylase

Answer 27

* *pre-exhisting glycogen polymer* serves as primer to which glucose units are added * Glycogen synthase (**rate limiting enzyme**) catalyzes transfers of glucose from UDP-glucose to non reduing end of lcogen chain. forms alpha - 1-4 bond s between glucose molecules

Answer 28

via UDP glucose and glycogen using glycogen synthase

Answer 29

* when glycogen chain reaches 11 residues, a fragment of the cain (about 7 residues long) is broken off at an alpha -1,4 link and reattached elsewhere through an alpha -1,6 link by glucosyl (4:6) transferase * The new branch point must be at least 4 residues away from a pre-exhisting branch * branching increases solublity of glyogen and increases number of terminal non-reducing ends * increases rate at which glycogen can be sythesized and degraded ( glycogen (4:6) transferase leads to creation of more non reduced ends )

Answer 30

* glycogen broken down to release glucose-1-phosphate * glycogen remnant remodeled to permit futhur degradation * glucose -1-phosphate converted to glucose -6-phosphate * Gylcolysis * free glucose for release into blood strream * pentose phosphate pathway * NAPH and ribose derivative

Answer 31

* One to degrade glycogen (Chain shorten) * **glycogen phosphorylase** * Two to remodel glycogen remnants * **phosphoglucomutase** * converts gluc-1-phosphate to Gluc-6-phosphate * **transferase** * One to convert glycogen break down * Product suitable for further metabolism * **alpha1,6-glucosidase** fill out later

Answer 32

* **Glycogen phosphorylase(GP) = rate limiting enzyme catalyzes the cleavage of glycogen** * Chain shortening occur at the non reducing end of the polymer (similiar to glycogen synthase) GP adds an orthophosphate and releases a glucose residue as glucose-1-phosphate * Uses pyridoxal phosphate (vitamin B6) as a cofactor * Phosphorolysis of glucose residues continues till the GP gets within 4 residues of the alpha-1,6 linkage of a branch point

Answer 33

Converts gluc-1-phosphate to gluc-6-phosphate A phosphoryl group is transferred from the enzyme to the substrate, and a different phosphoryl group is transferred back to restore the enzyme to its initial state

Answer 34

* **Transferase** transfers a block of 3 of the remaining 4 glucose to the non-reducing end of the main chain forming an alpha-1,4 bond * debranching enzyme or alpha-1,6 glucosidase cleaves the alpha 1,6 bond of the single remaining glucose residue to trelease the free glucose. Glucose phosphorylated by hexokinase * **Transferase** and alpha 1,6 glucosidase conerted branch glycogen into a linear structure for futhrur action by GP

Answer 35

* Converts G6P to glucose which can be released in blood stream ebcause G6P cannot get out of the cell * Only the liver has glucose 6- phosphatase * muscle cells do not have glucose 6-phosphatase so gluc-6-phosphate stays

Answer 36

gluc-6 -phosphate favors glycogen synthesis

Answer 37

active "a" form (R relaxed state "phosporylated ) in liver = glycogen phosphorylase A INactive "b" form ( tense state) in muscle = glycogen phosphorylase B

Answer 38

* low blood sugar * ephineprine * glucoagone * glycogen break down promoted * glycogen synthesis inhibited * High blood suga * insulin * glycogen synthesis promoted * breakdown inhibited

Answer 39

know both of these diagrams (no comparsons just understand them )