BIO chem enzymes step1 contd Flashcards
This patient presents with a painful upper extremity rash, malnutrition, diarrhea, and mental status changes. Individuals who are homeless or affected by alcohol use disorder are at risk for developing dietary vitamin deficiencies. Based on his symptoms, the most likely diagnosis is ?
niacin (vitamin B3) deficiency, also called pellagra.
The symptoms of pellagra are classically described as the 3 D’s: Diarrhea, Dementia, and Dermatitis. If untreated, pellagra can result in ?
the fourth D: death. Glossitis is another important symptom of niacin deficiency that is not included in the 3 D’s. Pellagra is an Italian word meaning “thickened skin,” which describes the hyperpigmentation on sun-exposed areas of the body (as seen in the image). The rash’s circumferential distribution in the C3/C4 dermatome is known as the “Casal necklace.”
Because niacin is derived from ?
tryptophan, a decrease in tryptophan absorption or an increase in tryptophan metabolism can produce similar symptoms. Other potential causes of niacin deficiency include malignant carcinoid syndrome (increased tryptophan metabolism) or isoniazid therapy (decreases pyridoxine [vitamin B6] required for niacin synthesis).
Although a deficiency of biotin (vitamin B7), pantothenic acid (vitamin B5), or zinc could lead to ?
- Thiamine (vitamin B1) deficiency can lead to ?
dermatologic changes, none of these would explain the patient’s cognitive decline.
- confusion and confabulation (Wernicke-Korsakoff syndrome), but it is not associated with a rash or diarrhea.
A deficiency of niacin (vitamin B3), tryptophan, or pyridoxine (vitamin B6) can lead to pellagra. Patients with niacin deficiency classically present with ?
the triad of diarrhea, dementia, and dermatitis.
A new small-molecule drug for the treatment of HIV has just been discovered. This small molecule appears to bind to a newly discovered surface G-protein–coupled receptor (GPCR), TTY2, and sets off a cascading signal that leads to apoptosis of the cell. The TTY2 receptor is expressed in cells that have been infected by HIV but is not expressed in noninfected cells. Using in vitro experiments, scientists have been able to show that binding of the TTY2 receptor will act on phospholipase C, thereby leading to an increase in intracellular calcium.
The TTY2 receptor is similar to which of the following receptors?
α1
When activated, the Gq class of GPCRs results in activation of protein kinase C and an increase in intracellular calcium. Thus, like the TTY2 receptor, the α1-adrenergic receptor is a Gq-class GPCR. Other Gq-class GPCRs include muscarinic1, muscarinic3, and histamine1.
Gq-class receptors include muscarinic1, muscarinic3, and histamine1. Gq-class receptors activate phospholipase C, causing an increase in inositol triphosphate (which leads to calcium release in the cell) and diacylglycerol, which leads to protein kinase C activation.
This patient’s history of poor oral intake, hemarthrosis, anemia, and signs of microhemorrhage are consistent with vitamin C deficiency, also known as scurvy, which also results in?
impaired collagen synthesis. Several vitamin deficiencies cause anemia and other hematologic disorders, but scurvy is characteristically associated with gum bleeding and swelling as well as poor wound healing. Vitamin C is vital for proline hydroxylation in collagen synthesis; therefore, deficiency of this vitamin will cause defects in structures requiring collagen.
Vitamin K deficiency, caused by ?
- Vitamin A deficiency impairs?
impaired carboxylation of glutamic acid, manifests primarily as failure to clot and hemorrhage.
- the immune response, leading to night blindness, GI and respiratory problems, and other skin disorders.
The electron transport chain is located on inner mitochondrial membrane and is the site of oxidative phosphorylation. The enzymes involved in this metabolic pathway are the targets of many drugs and poisons that inhibit their activities.
Which agent directly inhibits the complex that serves as the final electron acceptor in the electron transport chain?
Cyanide binds to the Fe3+ of cytochrome aa3, the fourth and final complex in the electron transport chain. This prevents the final transfer of electrons to oxygen and halts any further oxidative phosphorylation. Inhalation of high doses of cyanide leads to coma, with seizures, apnea, cardiac arrest, and death.
Antimycin A is an antibiotic that binds to cytochrome c reductase and prevents ?
the transfer of an electron from cytochrome b to cytochrome c in the electron transport chain.
2,4-Dinitrophenol is a chemical used to make dyes, as well as a cellular metabolic poison. It uncouples ?
oxidative phosphorylation by carrying protons across the mitochondrial membrane. The energy produced by the transport of electrons is released as heat rather than being used to synthesize ATP. In high doses, the drug aspirin (and other salicylates) uncouples oxidative phosphorylation, which explains why a fever can accompany toxic overdoses of these drugs.
Oligomycin is an antibiotic that binds to ATP synthase and blocks?
the reentry of protons into the mitochondrial matrix. Because the pH and electrical gradients cannot be dissipated, further electron transport stops because of the difficulty of pumping any more protons against the steep gradients. Since electron transport and oxidative phosphorylation are tightly coupled, any inhibition of one leads to inhibition of the other.
Rotenone inhibits?
the transfer of electrons to ubiquinone in the electron transport chain. It is commonly used in insecticides and pesticides.
This man presents with worsening weakness and fatigue, as well as bruising, swollen gums, and possible poor immune function. In the context of probable malnutrition, he most likely has scurvy. In addition to the patient’s homeless state and his description of erratic eating, the odor of alcohol on his breath suggests a possible history of alcoholism and associated poor overall nutrition. Alcoholism and poor nutrition can result in?
vitamin C (ascorbic acid) deficiency. As a result, proline and lysine are not hydroxylated in the endoplasmic reticulum during the formation of collagen. This leads to manifestations including ecchymoses, petechiae, bleeding gums, and the characteristic corkscrew hairs.
Collagen formation does not involve any of the following: glycosylation of proline and lysine in the endoplasmic reticulum, hydroxylation of proline and isoleucine in ?
the Golgi apparatus, or glycosylation of proline with either isoleucine or lysine in the Golgi apparatus. Only asparagine, serine, threonine and rarely post-translationally hydroxylated amino acids can undergo glycosylation.
