GLUCONEOGENESIS :: آموزش و تدریس بیوشیمی آموزش و تدریس بیوشیمی آموزش نکته به نکته بیوشیمی برای تمامی مقاطع بخصوص کنکور کارشناسی ارشد و دکتری آموزش و تدرس مباحث درس بیوشیمی، به صورت گام به گام، نکته به تکته برای کنکور کارشناسی ارشد و دکتری طبقه بندی موضوعی کلمات کلیدی آخرین مطالب پربیننده ترین مطالب محبوب ترین مطالب GLUCONEOGENESIS Where does the majority of gluconeogenesis occur? Mainly in the liver, and to a lesser extent in the kidneys and intestinal epithelium Name four substrates that can be used for gluconeogenesis: 1. Lactate 2. Pyruvate 3. Glycerol 4. Substances that can be converted to oxaloacetate (amino acid carbon skeletons) Name four enzymes that circumvent the irreversible steps in glycolysis: 1. Pyruvate carboxylase 2. PEP carboxykinase 3. Fructose-1,6-bisphosphatase 4. Glucose-6-phosphatase Where in the cell can pyruvate carboxylase be found? Mitochondria What reaction does pyruvate carboxylase catalyze? Pyruvate → oxaloacetate (which leaves the mitochondria) Pyruvate carboxylase requires what coenzyme in order to function? Biotin What molecule in excess activates pyruvate carboxylase? Acetyl CoA Where in the cell can PEP carboxykinase be found? Cytosol and mitochondria What reaction does PEP carboxykinase catalyze? Oxaloacetate → PEP What triphosphate must be present in order for PEP carboxykinase to function? What is the major manifestation of PEP carboxykinase defi

DISACCHARIDE METABOLISM :: آموزش و تدریس بیوشیمی آموزش و تدریس بیوشیمی آموزش نکته به نکته بیوشیمی برای تمامی مقاطع بخصوص کنکور کارشناسی ارشد و دکتری آموزش و تدرس مباحث درس بیوشیمی، به صورت گام به گام، نکته به تکته برای کنکور کارشناسی ارشد و دکتری طبقه بندی موضوعی کلمات کلیدی آخرین مطالب پربیننده ترین مطالب محبوب ترین مطالب DISACCHARIDE METABOLISM What is the primary dietary source of fructose? Dietary fructose is consumed primarily as the disaccharide sucrose (glucose fructose), also called table sugar. Uptake of fructose is by insulin-independent GLUT-5 and does not promote insulin release. What enzymatic reaction does sucrose catalyze? Sucrose → glucose + fructose Where does the majority of fructose metabolism occur? What is the first step in fructose metabolism? Hexokinase converting fructose to fructose-6-phosphate in the muscle and kidney Fructokinase converting fructose to fructose-1-phosphate in the liver Is the rate of fructose metabolism faster or slower than that of glucose? Why? Fructose metabolism is faster because it bypasses the key rate-limiting enzyme of glycolysis, PFK-1 How do the kinetics of fructokinase and glucokinase differ? Fructokinase has a high affi nity (low Km) for fructose and a high Vmax. Glucokinase, the hepatic hexokinase that phosphorylates glucose, has a low affinity for fructose. Essential fructosuria results from a deficiency in what enzyme? Fructokin

HEXOSE MONOPHOSPHATE SHUNT What are the substrates for the pentose/hexose phosphate or hexose monophosphate (HMP) shunt? Glucose-6-phosphate and nicotinamide adenine dinucleotide phosphate (NADP+) Where in the cell does the HMP shunt occur? What organs in the body have extensive HMP shunt activity? Lactating mammary glands, liver, adrenal cortex (erythrocytes also have HMP shunt activity) What characteristic do these organs share? Sites of fatty acid or steroid synthesis What is the rate-limiting enzyme in the HMP shunt? Glucose-6-phosphate dehydrogenase (G6PD) Name an activator of the G6PD enzyme: Name an inhibitor of the G6PD enzyme: What are the major products of the HMP shunt? Ribose-5-phosphate and NADPH In what process is ribose-5-phosphate utilized? In nucleotide synthesis List three important processes which utilize NADPH: Anabolic processes (as a source of reducing equivalents) 2. Respiratory/oxidative burst—rapid release of reactive oxygen species by cells (e.g., by immune cells to fight bacteria) 3. Hepatic P-450 function How do RBCs utilize NADPH? Via the glutathione reductase enzyme to reduce glutathione List four important processes which utilize glutathione: Reduction of protein sulfhydryl groups Reduction of peroxidases Maintenance of reduced hemoglobin (Hgb) “Catching” amino acids in the extracellular space (via γ- glutamyltranspeptidase) Why are RBCs particularly vulnerable to oxidative damage? RBCs have the capacity to carry large amounts of O2 and