Metabolism Flashcards
“Musty odor”, Intellectual disability, eczema. What is the disease and pattern of inheritance? Defective enzyme?
What amino acid becomes essential?
PKU (Phenylketonuria). Autosomal RECESSIVE.
Defective enzyme: Phenylalanine hydroxylase.
Tyrosine becomes essential.
Baby has pee that smells like “burnt sugar” and isn’t feeding well. What should they avoid, and what is the general disorder?
Maple Syrup Urine disease. It’s a blocked degradation of branched amino acids (branches, like maple tree branches). Remember, maple from Vermont, “I Love Vermont”, Isoleucine, Leucine, Valine.
True or False? Binge eating followed by fasting and intense exercise is NOT a form of bulimia nervosa? How do bulimia and binge eating disorders differ? Where does anorexia fit into all of this?
False. This is bulimia. Bulimia consists of binge eating followed by compensatory measures (ie vomiting, exercise). Binge eating disorder is binge eating with no compensatory measures. Anorexia is just significantly low weight.
A patient presents with a burning sensation on his palms and soles, doesn’t sweat much, has angiokeratomas (papules in the groin area)….What’s the diagnosis? What enzyme is deficient? What is he at risk of developing?
Fabry disease. Alpha-galactosidase deficiency leads to sphingolipid (globotriaosylceramide) accumulation. Risks=renal failure, LVH, and strokes/transient ischemic attack
A little kid comes in with abnormal movements and growth delay. His tests show elevated arginine. What process is disrupted, and what is normally produced from the metabolism of arginine?
There is an arginase deficiency, so the urea cycle is getting messed up. Arginine is usually metabolized to urea and ornithine. Treatment includes an arginine-free diet.
What are the 3 D’s of niacin deficiency? What AA is niacin derived from?
3 D’s: Dermatitis, Diarrhea, Dementia.
Skin exposed to sun is worse.
Rough skin=pellagra.
This doesn’t actually belong here, but what are the start and stop sequences for spliceosomes?
Start: GU
Stop: AG
If a kid has elevated methionine levels, what should you suspect, and what AA becomes essential?
Elevated methionine means that they probably have homocystinuria.
As a result, cysteine becomes essential because they aren’t producing cysteine from methionine.
For glycogen synthesis and glycogenolysis, what are the roles of Protein Phophatase and Protein Kinase A?
Protein Phosphatase: Activated by tyrosine kinase receptor (P13 pathway) to promote glycogen synthase (synthesis). It blocks gylcogen phosphorylase.
Protein Kinase A: Activated by Adenylate cyclase (cAMP), activates glycogen phosphorylase kinase.
Self mutilation, hyperuricemia in a baby. What’s the condition, what enzyme is deficient, and what enzyme will be overactive, and why?
Lesch-Nyhan Syndrome (X-linked Recessive)
Hypoxanthine-Guanine phosphoribosyltransferase (HGPRT) is deficient. Since this is purine salvage pathway, you need more de novo purine synthesis.
For de novo, Phosphoribosyl pyrophosphate (PRPP) is increased.
What are the steps of Vitamin D metabolism? Where do they occur?
7-dehydrocholesterol—-> Vitamin D3 (cholecalciferol) occurs in skin.
Vitamin D3/Vitamin D2 (ergocalciferol)—–>25-hydroxyvitamin D occurs in liver.
25-hydroxyvitamin D—->1,25 dihydroxy vitamin D occurs in kidney
Perifollicular petechial hemorrhages, gingivitis, subperiosteal hematoma, myalgias in someone who only eats bread and canned meat. Diagnosis?
Scurvy–a lack of ascorbic acid (Vitamin C)
A patient has Tay Sach’s disease (cherry red spot, easy scare reflex). What metabolite has accumulated?
It’s a sphingolipid disorder.
GM2 ganglioside has accumulated (due to beta-hexosaminidase A deficiency).
Differs from Niemann-Pick b/c Tay Sach’s has no hepatomegaly.
A patient has niacin deficiency. What would be clinical signs, and what enzyme likely now has deficient activity?
3 D’s of B3 (Niacin=Vitamin B3).
Diarrhea, Dementia, and Dermatitis (Pellagra).
Niacin is a precursor to NAD, which is a cofactor for many dehydrogenase and reductase enzymes.
So Niacin–>NAD–>Dehyrdrogenase/Reductase.
What is a common finding in patients with untreated PKU (ie at autopsy)? What enzyme is deficient?
Hypopigmentation of skin, hair, eyes, and catecholaminergic brain nuclei (ie substantia negra).
Enzyme=phenylalanine hydroxylase.
This is due to accumulation of phenylalanine in body fluids and the CNS.
*remember to look for a child that was normal at birth but then developed issues, intellectual delay, etc.
