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Biochemistry 2.1

UWORLD + FA biochemistry review

QuestionAnswer
Photosensitivity manifests as a VESICLE AND BLISTER formation on sun-exposed areas, as well as edema, pruritus, pain and erythema
Photosensitivity is seen in _____________ steps of ______________ synthesis. LATE; Porphyrin
Why is photosensitivity seen with late steps of porphyrin synthesis? due to accumulation of porphyrinogens that react with oxygen excited by UV-light
What is a common porphyrin disorder associated with photosensitivity? Porphyria Cutanea Tarda (PCT)
PCT is caused by deficiency of which enzyme? Uroporphyrinogen decarboxylase (UROD)
PBG deaminase deficiency causes? Acute intermittent porphyria (AIP)
Which is associated with photosensitivity, AIP or PCT? PCT
Abdominal pain, neuropsychiatric symptoms and PBG accumulation? AIP
What is the function of vWF? bids to glycoprotein IB receptors on platelets to mediate platelet adherence after endothelial damage.
Deficiency of vWF can cause abnormal? Ristocetin agglutination assay
In cases of vWF deficiency, the administration of ________________, causes a normal ristocetin agglutination on assay. Desmopressin
Low levels of vWF cause poor agglutination in the presence of ristocetin
What are key vignettes features of a woman with vWF deficiency? Gingival bleeding and heavy menses
Bernard-Soulier syndrome: Hereditary deficiency of GP Ib receptors
What is the clinical presentation of Bernard-Soulier syndrome? Thrombocytopenia, enlarged platelets, and mucocutaneous bleeding
Why is there no agglutination of ristocetin in Bernard-Soulier syndrome, upon addition of normal serum (or desmopressin)? There is a lack of GP Ib receptors and not vWF
Glanzmann thrombasthenia: Hereditary deficiency of GP IIb/IIIa receptors
How is the risotein agglutination test in Glanzmann thrombasthenia? Normal, since GP Ib receptor and vWF are normal.
What is the Hageman factor? Factor XII (12)
Deficiency of Hageman factor causes? Thrombotic events and not associated with bleeding.
What are the cofactors needed or used by Branched-chain alpha-ketoacid dehydrogenase? Thiamine, Lipoate, Coenzyme A, FAD, and NAD
What illness is associated with mutated branched amino acid enzyme? Maple Syrup Urine disease
Maple Syrup Urine disease requires of _____________ supplementation to improve symptoms, and lifelong restriction of ______________, __________, and ___________. Thiamine; Restriction of : Valine, Leucine, and Isoleucine
What enzyme is responsible to initiate the cascade of Pyruvate to produce Energy? Pyruvate dehydrogenase
Pyruvate + Pyruvate dehydrogenase -----> Acetyl-CoA
In Pyruvate metabolism, an excess amount of Acetyl-CoA accumulation will cause? 1. Inhibition of Pyruvate dehydrogenase (stop making energy) 2. Stimulate (increase/accelerate) Pyruvate carboxylase activity, in order to make more Oxaloacetate ---> Glucose
Pyruvate + CO2 + Pyruvate carboxylase ------> Oxaloacetate
Gluconeogenesis produces ----> Glucose
Increased amounts or concentration of Oxaloacetate causes: Inhibition of and slowing of Pyruvate carboxylase activity.
G6PD: is a rate limiting enzyme of the PPP
What is the major source of cellular NADPH synthesis? Pentose Phosphate Pathway (PPP)
The PPP is the major source of intracellular _____________. NADPH
NADPH is necessary for: 1. Reducing agent (protects RBC from oxidative damage) 2. Biosynthesis of cholesterol, fatty acids, and steroids 3. Phagocytic cells generating a respiratory burst via NADPH oxidase.
G6PD deficiency: It is seen with acute hemolytic anemia and jaundice. Usually after consumption of fava beans.
HbS: aggregates in the deoxygenated state
HbS polymers: form fibrous strands that reduce RBC membrane flexibility and promote RBC sickling
Sickling: Occurs under circumstances that are associated with ANOXIA including low pH and high levels of 2,3-BPG
Sickle cells are predisposed to ________________ ____________ and _________________, especially in the __________ and ______, due to __________ blood flow. Microvascular occlusion and Microinfarcts; Liver and Spleen due to slow blood flow.
Which organs tend to produce the highest rate of RBC sickling and why? The organs that have increased and heavy blood flow such as the brain, muscles and placenta, due to increase extraction of oxygen from the blood (Oxygen unloading)
Oxygen unloading is: Extraction of oxygen by tissue from the blood
What enzyme is inhibited by Isoniazid? Pyridoxal phosphokinase
An inhibition of Pyridoxal phosphokinase leads to: Vitamin B6 (Pyridoxine) deficiency
Pyridoxine active form: is a cofactor for s-aminolevulinate synthase, the enzyme that catalyzes the rate-limiting step of heme synthesis
What inhibition is responsible for causing Sideroblastic anemia? Inhibition of limiting step of heme synthesis (s-aminolevulinate synthase)
PBS shows an RBC with a "ring" formation around nucleus of "blue" granules. Dx? Sideroblastic anemia
What are the steps (in order) of Base Excision repair? 1. Glycosylase 2. Endonuclease 3. Lyase 4. DNA polymerase 5. Ligase
Mnemonic for remembering steps of Base excision repair process? GEL-PL
In what organelle does the hydroxylation of Lysine and Proline residues occur during collagen synthesis? Rough Endoplasmic Reticulum
Collagen gets it maximum tensile strength from which part of its synthesis process? Hydroxylation of Proline and Lysine residues in the RER
Hydroxylation of Proline and Lysine in collagen synthesis uses ________________ as a cofactor. Vitamin C
Vitamin C deficiency is known as _____________________. Scurvy
Scurvy: Vitamin C deficiency that produces fragile vessels, predisposing to gingival bleeding, ecchymosis, and petechiae
Thiamine is a cofactor for which 4 enzymes: 1. Pyruvate dehydrogenase (pyruvate ---> Acetyl-CoA --> Kreb) 2. alpha-KG dehydrogenase (enzyme of Citric cycle) 3. Transketolase (enzyme in PPP) 4. Branched-chain a-ketoacid dehydrogenase (catabolism of branched amino acids)
Vitamin B12 deficiency: - Elevated levels of Methylmalonic acid and Homocysteine - Neurological symptoms and megaloblastic anemia - Subacute combined degeneration: * Dorsal columns -- loss of prioception/vibration, and (+) Romberg sign * Lateral corticospinal tract -- Spastic muscle weakness, hyperreflexia
Vitamin B9 (Folate) deficiency: Only has elevated level of Homocysteine and with no neurological deficits.
Niacin Precursor for NAD and NADP
NAD is used for: Catabolic reactions (glycolysis and B-oxidation) Citric cycle for: - Isocitrate dehydrogenase - a-KG dehydrogenase - Malate dehydrogenase
Fabry disease pathophysiology? X-R disorder; due to alpha-galactosidase A deficiency resulting in the accumulation of sphingolipid globotriaosylceramide
What are some clinical features of Fabry disease? Neuropathic pain, Angiokeratomas Telangiectasias Glomerular disease (Proteinuria) Cerebrovascular disease (TIA, stroke) Cardiac disease (LVH)
Metachromatic leukodystrophy: due to arylsulfatase A deficiency resulting in accumulation of cerebroside sulfate
Clinical manifestation of Metachromatic leukodystrophy: Progressive demyelination leading to ataxia, peripheral neuropathy, seizures and hypotonia
Niemann-Pick Disease: accumulation of Sphingomyelin due to deficiency of Sphingomyelinase.
What are some clinical characteristics seen in Niemann-Pick disease? Progressive neurodegeneration, cherry-spot in macula and hepatosplenomegaly. Associated with chromosome 11
Which Lysosomal enzyme condition is associated with chromosome 15? Tay-Sachs disease
What is the distinguishing feature between Niemann - Pick disease and Tay-Sachs disease? Niemann-Pick disease presents with Hepatosplenomegaly.
What lysosomal conditions present with hepatosplenomegaly? Niemann-Pick disease, Hunter disease, and Hurler disease
Krabbe disease is due: Galactocerebrosidase deficiency resulting in accumulation of Galactocerebroside and psychosine.
How is Krabbe disease presented: Peripheral neuropathy, destruction of oligodendrocytes, developmental delay , optic atrophy, adn globoid cells.
Gaucher's disease: AR; "crumpled tissue paper"; Deficiency glucocerebrosidase and accumulation of glucocerebroside. Associated with chromosome 1.
"Whorled membrane" Tay-Sachs disease
Galactosemia is due to deficiency in which two enzymes: 1. GALK (Galactokinase) 2. GALT (Galactose-1-phosphate uridyl transferase)
Which galactosemia is the mild form? GALK deficiency
GALK deficiency Galactosemia is mostly asymptomatic except for: Lenticular accumulation of galactitol in the lenses, causing osmotic damage and development of cataracts.
Excess in galactose and or fructose in urine yield: Urine test positive for reducing agents
Which galactosemia enzyme deficiency develops into severe presentation of the disease? GALT deficiency
What is the clinical presentation of GALT deficiency? Severe galactosemia; Hepatic and renal failure; Usually presents n neonates with vomit, lethargy and failure to thrive.
Aldolase B deficiency Hereditary FRUCTOSE intolerance
Inability to metabolize fructose, causing hypoglycemia, hypophosphatemia,and failure to thrive Aldolase B deficiency
What determines the sequence of amino acids? The interaction of the mRNA codons with the tRNA anticodon.
What happens with a mischarged tRNA with the wrong amino acid? In case of failing correction by the aminoacyl(AA)-tRNA synthase proofreading, the wrong amino acid will be integrated to the growing polypeptide chain.
What kinds of agents are used to treat CN poisoning? Nitrates
Why are nitrates used to treat CN toxicity? ability to induce methemoglobinemia
Methemoglobinemia: Binds tightly to CN; causes a dusky discoloration of the skin and cannot carry oxygen
Methemoglobin contains ______ (___) instead of _______ (__). Ferric (Fe3+); Ferrous (2+)
Which type of iron state binds more tightly to mitochondrial enzymes, thus reducing the CN toxic effects? Ferric iron (Fe 3+)
Clinical presentation of CN toxicity? Reddish skin discoloration, tachypnea, headache and tachycardia. Seen with Lactic acidosis with a narrow venous-arterial O2 gradient
What enzyme is in charge of correcting wrong tRNA anticodon amino acid? aminoacyl-tRNA synthetase
BH4: tetrahydrobiopterin
MC disorder due to a BH4 deficiency? Phenylketonuria
What are the two main causes of Phenylketonuria? 1. PAH deficiency 2, BH4 deficiency
MCC of BH4 deficiency? Deficiency of dihydrobiopterin reductase, which reduces BH2 tin GH4.
BH4 is an important cofactor for? 1. Phenylalanine hydroxylase 2. Tyrosine hydroxylase
What are the 4 Dopaminergic pathways? 1. Mesolimbic --(positive symptoms of schizophrenia) 2. Mesocortical --(negative symptoms) 3. Nigrostriatal pathway -- EPS 4. Tuberoinfundibular --- Hyperprolactinemia
Glycogen storage disease type V: McArdle Disease
Enzyme deficient in McArdle disease? Myophosphorylase
What is the clinical presentation of McArdle disease? Muscle glycogenolysis, which resulted in decreased exercise tolerance, muscle pain and cramping, and myoglobinuria with physical activity
How are the lactic acid level in McArdle disease? Normal
On which organ does McArdle disease occurs? Muscle
Myophosphorylase: - isoenzyme of glycogen phosphorylase - during glycolysis it shortens the chains by clavein a-1,4-glycosidic linkages, liberation Glucose-1-phosphate
At what point does the cleaving done by myophosphorylase stop? At point of reaching the "limit dextrin"
What is the Limit dextrin? Glycogen chain with only 4 residuels left
What is liberated during glycogenolysis by the action of myophosphorylase? Glucose-1-phosphate
What it's the aerobic fate of Pyruvate? Converts into Acetyl-CoA by using Pyruvate dehydrogenase, which then enters the TCA
What is the anaerobic fate of Pyruvate? Becosmes Lactic acid, by the enzyme Lactate dehydrogenase
Pyruvate + CO2 + _____________-----> Oxaloacetate --> ___________. Pyruvate carboxylase; Glucose
GTP is synthesized by __________ during the TCA cycle conversion of _____________ to _____. Succinyl-CoA synthase; Succinyl-CoA into Succinate
Which reaction requires GTP as cofactor in GLUCONEOGENESIS? PEP carboxykinase uses GTP to synthesis PEP form Oxaloacetate
What is splicing? Performed by splicesosomes; Removal of introns
What introns are removed during splicing? 1. GU at the 5' splice site 2. AG at the 3' splice site
Mutations to the splice sites cause? inappropriate removal of exons, and retaining introns ---> dysfunctional proteins
Created by: rakomi