Question | Answer |
In which tissues does galactose metabolism occur? | Liver, erythrocytes, fibroblasts |
What enzyme is defective in hereditary fructose intolerance? | Aldolase B |
What enzyme is deficient in essential fructosuria? | Fructokinase |
For what purpose is fructose made in humans? | Fuel for spermatazoa |
In which tissue is fructose made for spermatozoa fuel? | Seminal vesicles |
What is the cause of classical galactosemia? | Galactose 1-phosphate uridyl transferase deficiency |
What is the cause of non-classical galactosemia? What are the symptoms? | Galactokinase deficiency; cataracts, no brain damage |
What type of glycosidic bond does lactose have? | B-1,4 |
What type of glycosidic bond does sucrose have? | a, B-1,2 |
What enzyme is responsible for digesting Cellobiose (glucose B-1,4 glucose)? | None |
What enzyme is responsible for digesting Maltose (glucose a-1,4 glucose)? | Glucoamylase / sucrase-isomaltase |
What enzyme is responsible for digesting Isomaltose (glucose a-1,6 glucose)? | Sucrase-Isomaltase |
What enzyme is responsible for digesting Lactose (galactose B-1,4 glucose)? | Lactase |
What enzyme is responsible for digesting sucrose (glucose a, B-1,2 fructose)? | Sucrase |
What enzyme is responsible for digesting trehalose (glucose a, a-1,1 glucose)? | Trehalase |
What disaccharide cannot be digested by the sucrose-isomaltase complex? | glucose a,a-1,1 glucose |
GLUT-1 | Red blood cells, blood brain barrier |
GLUT-2 | Liver, Pancreatic B-cells, contraluminal membrane of intestinal epithelial cells (accepts all 3 monosaccharides) |
GLUT-3 | Brain |
GLUT-4 | Adipose tissue, skeletal muscle, heart muscle (insulin sensitive) |
GLUT-5 | Intestinal epithelial cells, sperm (fructose transporter) |
SGLT-1 | Intestinal epithelial cells (Na dependent) |
SGLT-2 | Kidney (Na dependent) |
Glucose uptake by muscle is stimulated by what? | AMP |
AMP-stimulated protein kinase translocation of GLUT-4 is generated in what reaction? | Adenylate kinase reaction |
The liver is insulin dependent/independent? | Independent |
True/False: Under low glucose conditions glucokinase is bound to GKRP in the hepatocyte nucleus. | True |
True/False: Under high glucose conditions glucokinase is bound to GKRP in the hepatocyte nucleus. | False, it is released from GKRP, travels to cytoplasm and phosphorylates glucose. |
True/False: Hexokinase is found in all tissues and is inhibited by glucose 6-phosphate. | True |
True/False: In the absence of a glycogen fragment, a specific protein, glycogenin, can serve as an acceptor of glucose residues. | True |
True/False: Glycogenin transfers a few molecules of glucose from UDP-glucose to form a short chain to be further elongated by glycogen synthase. | True |
The enzyme responsible for cleaving a block of 5-8 residues and reattaching them at a more interior site is | Glucosyl transferase |
What does phosphorylase do to glucose residues? | Removes glucose residues from the nonreducing ends to form glucose 1-P. |
What does glycogen synthase do to a glycogen molecule? | It transfers glucose from UDPG to a nonreducing end of a pre-existing glycogen molecule. |
What does phosphoprotein phosphatase-1 do when bound to its inhibitor? | Once the inhibitor is activated by phosphorylation, it will bind to the phosphatase and inactivate it, removing its inhibition on active phosphorylase and inactive synthase. |
What three things does protein kinase A do? | Activates phosphorylase, inactivates synthase, and activates phosphatase inhibitor, all by phosphorylation. |
What are the key differences between epinephrine and glucagon? | Epinephrine acts in liver and muscle, glucagon acts just in liver. Epinephrine comes from adrenal medulla and glucagon comes from a-cells of pancreas. |
True/False: Glucagon binds to the glucagon receptor in the liver and activates adneylate cyclase, via G-proteins. cAMP binds to protein kinase A. | True |
True/False: Protein kinase A activates phosphorylase kinase by phosphorylation, which in turn, phosphorylates glycogen phosphorylase b, thereby converting it to the active phosphorylase a. | True |
What are three kinases that phosphorylate glycogen synthase? | Protein kinase A, phosphorylase kinase, glycogen synthase kinase-3 (GSK-3) |
What enzyme is activated by insulin and decreases cAMP? | Phosphodiesterase |
What membrane bound enzyme is activated when epinephrine binds to a-receptors in the liver that involve G-proteins as the activator? | Phosholipase C (PLC) |
What two products are formed when PLC hydrolyzes phosphatidylinositol bisphosphate (PIP)? | Diacylglycerol (DAG) and inositol triphosphate (IP3) |
What does IP3 stimulate the release of from the endoplasmic reticulum? | Calcium |
Protein kinase C is activated by what two things? | Calcium and DAG |
The calcium-calmodulin complex activates what two enzymes? | Calmodulin-dependent protein kinase & Phosphorylase kinase |
What three enzymes all phosphorylate glycogen synthase when epinephrine is bound to a-agonist receptors? | Protein kinase C, Calmodulin-dependent protein kinase, and Phosphorylase kinase |
True/False: Insulin inactivates glycogen synthase kinase-3. | True |
AMP formed from ATP during muscular contraction binds to and activates what enzyme? | Glycogen phosphorylase b (active without phosphorylation) |
Where is calcium released from after nerve impulses initiate contraction? | Sarcoplasmic reticulum |
Once calcium is released into the cytosol of a muscle cell it binds to calmodulin, making a calcium-calmodulin complex that binds to and activates what enzyme? | Phosphorylase kinase (active without phosphorylation) |
True/False: The cascade caused by epinephrine in muscle is the same as in the liver. | True |
What is the defective enzyme in Von Gierke's Disease? | Glucose 6-phosphatase; causes massive enlargement of liver, hypoglycemia, ketosis, hyperuricemia, hyperlipemia |
What is the defective enzyme in Pompe's Disease? | a-1,4-glucosidase; causes cardiorespiratory failure and causes death before age 2. |
What is the defective enzyme in Cori's Disease? | amylo-1,6-glucosidase (debranching enzyme); causes massive enlargement of the liver, hypoglycemia, ketosis, hyperuricemia, hyperlipemia (milder course); muscle and liver. |
What is the defective enzyme in Andersen's Disease? | Branching enzyme; causes progressive cirrhosis of the liver and causes death before age 2. |
What is the defective enzyme in McArdle's Disease? | Phosphorylase; causes limited ability to perform exercise because of cramps. |
What is the defective enzyme in Hers' Disease? | Phosphorylase; causes massive enlargement of the liver, hypoglycemia, ketosis, hyperuricemia, hyperlipemia. |
What is the defective enzyme in VIII? | Phosphorylase kinase; causes mild liver enlargement and mild hypoglycemia. |