Chapter 1 Flashcards
To study for the Medical Biochemistry SHELF exam.
What does Isoniazid do?
Isoniazid combines chemically with pyridoxal, which results in the production of an inactive hydrazone derivative. In breast milk, isoniazid can achieve levels that are high enough to cause a vitamin B6 (pyridoxine) deficiency in the infant unless the mother is treated with vitamin B6 supplements
What enzyme is most active after a 24 hour fast?
Carbamoyl phosphate synthetase I
When is PFK-1 most active?
In the well-fed state
What is the importance of Vitamin C? What happens when there is a deficiency?
Vitamin C, as well as molecular oxygen and α-ketoglutarate, are the requirements for the proper function of prolyl hydroxylase, the enzyme responsible for hydroxylation of the proline side-chains in collagen. Collagen lacking such side-chain hydroxyl groups cannot be stabilized by interchain hydroxyl groups (cross-linkages between tropocollagen)
What are the symptoms of scurvy?
bleeding gums after brushing her teeth and pain in her legs when she walks.pinpoint areas of hemorrhage around the hair follicles, a smooth red tongue, gingivitis, dental caries, and ecchymoses scattered over the trunk
Where does the cleavage of the N- and C-terminal propeptides in collagen occur?
In the extracellular matrix.
Where does the triple helix assembly of procollagen occur?
This spontaneous process, which occurs in the Golgi apparatus, yields a procollagen molecule and does not require vitamin C
What are the symptoms of Glucose-6-phosphatase deficiency?
Deficiency of glucose-6-phosphatase leads to type I glycogen storage disease (von Gierke’s disease). Key features of this condition include a massively enlarged liver (although usually without cirrhosis), severe hypoglycemia, and failure to thrive. Glycogen accumulates in the liver and kidney (hepatorenomegaly)
What happens when there is a Glucosyl (4:6) transferase deficiency?
This child is exhibiting symptoms of type IV glycogen storage disease known as Andersen disease, a condition related to a deficiency of the glycogen branching enzyme glucosyl (4:6) transferase. This classically causes cirrhosis of the liver or cardiac tissue damage, usually with death occurring within the first one or two years of life. ALSO urine is negative for reducing substances. There are FEW long chains and VERY FEW branches.
The genes for two different proteins from a mammalian cell culture are overexpressed and the cDNAs of the two proteins are inserted into vectors that are then used to transfect human fibroblasts. What technique would be used to confirm that the transfections worked and the proteins were produced?
Western Blot
What does restriction mapping do?
Restriction maps allow for the detection of deletions or other rearrangements in a gene and not whether the cloned DNA was expressed
What does DNA sequencing do?
DNA sequencing shows only the sequence of a particular fragment of DNA and not whether the cloned DNA was expressed
A 42-year-old woman is being treated with aspirin and corticosteroids for systemic lupus erythematosus. Which of the following biochemical processes most likely is being inhibited by these drugs?
Prostaglandin formation
What inhibits the release of arachodonic acid?
Only corticosteroids block phospholipase A2, the enzyme that releases arachidonic acid from the cell membrane
What does thromboxane synthase do?
Neither corticosteroids nor aspirin blocks thromboxane synthase, which is located in platelets. This enzyme converts prostaglandin H2 into thromboxane A2, which is a vasoconstrictor and platelet aggregator.
What does PVT TIM HALL stand for?
Phenylalanine, Valine, Tryptophan, Threonine, Isoleucine, Methionine, Histidine, Leucine, Lysine
What are the Glucogenic amino acids?
Alanine, Glutamate, Aspartate
What are the Ketogenic amino acids?
Leu, Lys
What amino acids are glucogenic and ketogenic?
Ile, Trp, Phe
Why would you have increased blood and liver concentrations of VLDL in an alcoholic?
Ethanol is metabolized in the liver and eventually forms acetate, with NADH as another major product. Chronic consumption of ethanol causes a shift in the cytosolic balance between NAD+ and NADH in favor of NADH. The altered NAD+/NADH ratio causes less effective operation of the citric acid cycle, halts efficient oxidation of fatty acids, and causes a shift from dihydroxyacetone phosphate to glyceraldehyde 3-phosphate and eventually to glycerol 3-phosphate, the substrate for synthesizing triacylglycerol. The abundance of glycerol and free fatty acids results in an increased production of triacylglycerol, with increased export from the liver as VLDL, and fatty liver. These conditions are often seen in chronic alcoholics
What are the vitamin deficiencies in an alcoholic?
Vitamin B3/Niacin, B1/Thiamine/TPP, B2/riboflavin/FAD/FMN, B6/PLP, B12/Cobalamin, Vitamin A/ beta-carotene, Vitamin D, Vitamin E. Wernicke/Korsakoff Syndrome of B1/Thiamine.
What is another name for vitamin E?
Tocopherol.
Which of the following mechanisms best explains how phototherapy reduces the jaundice in this patient?
Oxidizes bilirubin to a water-soluble form
Explain the process of conversion of bilirubin to biliverdin.
Biliverdin, which is more water-soluble than bilirubin, is converted to bilirubin in macrophages before it is conjugated in the liver. Conversion of biliverdin to bilirubin is an energy-requiring reaction and is not reversed by phototherapy
An experiment is designed to determine how a specific protein functions in neuronal development. Which method will best determine how abundant the specific transcript for this protein is during different stages of development?
Northern Blot.
What is PCR good for?
Either the PCR technique or cloning can be used to amplify defined segments of DNA in vitro; however, a very limited amount of DNA can be amplified by PCR. The PCR technique is used in forensic medicine and prenatal diagnosis. Other applications of PCR include direct cloning, in vitro mutagenesis and engineering of DNA, and direct nucleotide sequencing of genomic DNA and cDNA
Which amino acid is most responsible for acidification of the urine?
Glutamine carries ammonia in the blood in a nontoxic state. In the proximal tubule of the kidneys, glutamine is converted by glutaminase to glutamate and ammonia, which eventually combines with protons in the collecting tubules to form NH4Cl. This process is the primary mechanism for the excretion of excess protons that leads to acidification of urine. Individuals who eat animal protein generate increased amounts of organic acids, which leads to excretion of more protons in the urine than would be excreted in the urine of pure vegans
What is present in ABUNDANCE in proteinuria?
This patient has symptoms of multiple myeloma, a proliferative disease that produces an abundance of ANTIBODY LIGHT CHAINS called Bence Jones proteins
Why would you get myoglobin in the blood?
Myoglobinuria can accompany muscle pain and weakness due to rhabdomyolysis (breakdown of muscle fibers and subsequent release of myoglobin)
A 28-year-old man has a family history of a disabling disorder that has caused the deaths of his father, grandfather, and two paternal aunts. The father and aunts died at a younger age than the grandfather, and it appears that the condition progressively worsens with each generation. What most likely is the disorder?
Huntington’s Disease.
A 4-year-old boy has a history of recurrent bacterial and fungal infections. Blood analysis shows that he has an undetectable gamma globulin fraction and increased concentrations of dATP in his white blood cells. What is the most likely diagnosis?
Adenosine deaminase deficiency.
What enzyme is deficient in Lesch-Nyhan syndrome?
Lesch-Nyhan syndrome results from a genetic deficiency in hypoxanthine-guanine phosphoribosyltransferase, leading to an alteration in nucleotide concentration but not to dATP accumulation
An 8-year-old boy is brought to the emergency department because of vomiting and convulsions. His urine has a fruity odor and is found to contain an elevated level of ketone bodies. Neurologic studies show central nervous system defects. Despite intensive treatment, the boy dies after several days. The disease most likely resulted from a deficiency of what enzyme?
Branched chain alpha keto acid dehydrogenase complex.
Deficiency of branched chain alpha keto acid dehydrogenase complex causes what disease?
Maple-syurp urine disease.
What happens in cystathionine synthase deficiency?
A deficiency of cystathionine synthase impairs the catabolism of methionine and causes homocystinuria.
What is deficient in Alkaptonuria?
A deficiency of homogentisic acid oxidase (homogentisate 1,2-dioxygenase) impairs the catabolism of tyrosine and causes alkaptonuria.
A radionuclide scan of the parathyroid glands shows a well-circumscribed mass in the right inferior parathyroid gland. Which of the following areas on the graph represents the most likely concentrations of parathyroid hormone (PTH) and calcium in this patient?
High PTH and High Ca+
What happens when there is a tumor on the parathyroid gland?
The patient has primary hyperparathyroidism resulting from a functioning parathyroid adenoma in the right inferior parathyroid gland. Recurrent [renal] calculi are the most common symptomatic presentation of this condition