Reading File
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
I now have strong textbook support for all answers. Here is the complete answer key with explanations:
Complete Answer Key - Biochemistry MCQs
Q18 - 30-year-old woman: Abdominal pain, psychiatric symptoms, elevated PBG (44 mg/24hrs)
18(i) Probable diagnosis: c) Acute Intermittent Porphyria (AIP)
The classic triad of AIP is abdominal pain, neuropsychiatric symptoms (hallucinations, mental changes), and muscle weakness. The markedly elevated urinary porphobilinogen (PBG) at 44 mg/24hrs (reference 0-4) is the hallmark. Porphyria cutanea tarda causes skin photosensitivity, not neuropsychiatric attacks. Congenital erythropoietic porphyria presents in childhood with severe photosensitivity.
18(ii) Enzyme defect: d) Uroporphyrinogen I synthase (= Hydroxymethylbilane synthase / HMB synthase)
Per Harper's Illustrated Biochemistry: "The defective enzyme in acute intermittent porphyria is hydroxymethylbilane synthase. ALA and porphobilinogen accumulate in body tissues and fluids." Note: This enzyme is also called porphobilinogen deaminase or uroporphyrinogen I synthase. Option (d) is the correct match from the choices given. Option (b) Uroporphyrinogen decarboxylase is defective in Porphyria Cutanea Tarda.
Q19 - 12-year-old boy: Skin tumour on right cheek, insensitive to sunlight
19(i) Probable diagnosis: c) Xeroderma Pigmentosum (XP)
A child with skin tumours (squamous/basal cell carcinoma) and sun sensitivity at a very young age is the textbook presentation of XP. Thalassemia does not cause skin tumours; Wilson's disease affects liver/brain; Emphysema is a lung disease.
19(ii) DNA repair defect: d) Nucleotide Excision Repair (NER)
Per Robbins & Kumar: "Several proteins are involved in nucleotide excision repair, and the inherited loss of any one of these can give rise to xeroderma pigmentosum." NER removes bulky DNA adducts caused by UV-induced pyrimidine dimers.
Q20 - Newborn using brown adipose tissue / Thermogenin (UCP1)
20(i) Primary mechanism: b) It increases the permeability of the inner mitochondrial membrane to protons
UCP1 (Thermogenin) works as a proton channel/carrier that allows protons to re-enter the mitochondrial matrix by bypassing ATP synthase (Complex V). This uncouples electron transport from ATP synthesis, releasing the energy as heat. It does NOT inhibit Complex V directly - it bypasses it.
20(ii) Effect on proton motive force and ATP yield: c) Decreases proton motive force and decreases ATP yield
UCP1 dissipates the proton gradient (reducing proton motive force) by allowing protons back in without going through ATP synthase. This means less proton gradient driving ATP synthesis, so ATP yield per glucose drops. The energy is released as heat instead.
Q21 - Leptin and obesity
21(i) ob/ob mouse mutation phenotype: c) Hyperphagia, obesity
The ob/ob mouse (lacking leptin) is the classic model of severe hyperphagia and morbid obesity. Without leptin, appetite is uncontrolled and energy expenditure is reduced. They do NOT develop hyperactivity or anorexia.
21(ii) Typical finding in common human obesity: b) High levels of leptin with evidence of leptin resistance
Per multiple textbooks including Robbins, Lippincott, and Harrison's: most obese humans have elevated circulating leptin (proportional to fat mass) but are resistant to its appetite-suppressing effects. Absolute leptin deficiency (option c) is extremely rare. This is why exogenous leptin has not been a successful obesity treatment.
Q22 - Carbon monoxide (CO) poisoning
22(i) Biochemical effect of CO on ETC: c) Inhibition of Cytochrome oxidase
Per Basic Medical Biochemistry and Fishman's Pulmonary Diseases: CO inhibits Complex IV (cytochrome c oxidase) by binding to the ferrous iron (Fe²+) of the heme center, blocking the transfer of electrons to oxygen. This halts the entire electron transport chain and oxidative phosphorylation.
22(ii) Mechanism of Valinomycin in disrupting Oxidative Phosphorylation: c) Acting as a potassium ionophore, dissipating the membrane potential
Valinomycin is a classic example of an ionophore uncoupler. It acts as a K⁺ ionophore - it carries potassium ions across the inner mitochondrial membrane, dissipating the electrochemical membrane potential (the electrical component of the proton motive force), thereby uncoupling ATP synthesis from electron transport. It does NOT transport protons directly (that would be a protonophore like DNP).
Q23 - Atherosclerosis
23(i) Initial triggering event (Response-to-Injury hypothesis): b) Chronic endothelial cell injury
The Response-to-Injury hypothesis states that atherosclerosis begins with chronic, repetitive injury to the vascular endothelium (from risk factors like hypertension, dyslipidemia, smoking, hyperglycemia). This initiates the inflammatory cascade. Rupture of the internal elastic lamina and thrombosis are later events.
23(ii) Modification of LDL for macrophage scavenger receptor recognition: c) Oxidation
LDL must be oxidized (oxidative modification) to be recognized by scavenger receptors (SR-A, CD36) on macrophages. Native LDL is not taken up by scavenger receptors. Oxidized LDL is the form that leads to foam cell formation in the subendothelial space.
Q24 - 3-day-old infant: Hyperammonemia, elevated orotic acid, undetectable citrulline
24(i) Enzyme deficiency: a) Carbamoyl phosphate synthetase I (CPS-I)
The key clues: undetectable citrulline (citrulline is made downstream of CPS-I and ornithine transcarbamylase) and normal anion gap. Wait - undetectable citrulline with elevated orotic acid points to OTC deficiency, not CPS-I. However, CPS-I deficiency also causes undetectable citrulline but with LOW/normal orotic acid. Here, orotic acid is markedly elevated - this is the key differentiator:
- CPS-I deficiency: low orotic acid (no excess carbamoyl phosphate to shunt into pyrimidine pathway)
- OTC deficiency: high orotic acid (carbamoyl phosphate accumulates and spills into cytoplasm)
Given elevated orotic acid: the answer is actually d) Ornithine transcarbamylase (OTC) deficiency. [The question stem says citrulline is undetectable AND orotic acid elevated - classic OTC deficiency.]
24(ii) Biochemical reason for elevated orotic acid: a) Accumulation of carbamoyl phosphate in the mitochondria which leaks into the cytosol
Per Basic Medical Biochemistry: when OTC is deficient, carbamoyl phosphate accumulates in mitochondria, leaks into the cytosol where CPS-II (the cytoplasmic enzyme) uses it to flood the pyrimidine synthesis pathway, producing excess orotic acid.
Q25 - Type 1 DM patient with DKA (glucose 500, pH 7.1, elevated ketones)
25(i) Primary mechanism of increased ketogenesis: c) Increased glucagon/insulin ratio leading to increased adipose tissue lipolysis
In DKA, absolute insulin deficiency with high glucagon causes: (1) massive lipolysis releasing free fatty acids, (2) increased fatty acid oxidation, (3) acetyl-CoA overflow into ketone body synthesis. Malonyl-CoA (option b) is actually LOW in DKA (not high), which removes the brake on carnitine acyltransferase, facilitating fatty acid entry into mitochondria.
25(ii) Why brain cannot use ketone bodies effectively at high concentrations: b) Lack of succinyl-CoA:acetoacetate CoA-transferase (thiophorase) in liver, not the brain
Wait - this is about the brain. The brain DOES have thiophorase (unlike the liver). The correct answer is b) Lack of succinyl-CoA:acetoacetate CoA-transferase (thiophorase) in liver, not the brain - but this is actually why the liver cannot use ketone bodies. The brain has this enzyme. At very high ketone concentrations in DKA, the brain IS actually using ketone bodies - the inability relates to the enzyme capacity being overwhelmed. The best answer from the choices: (b) - the liver lacks thiophorase (that's why it produces but doesn't use ketones), but the question asks about the brain at high concentrations. At extremely high concentrations, the limiting factor is thiophorase activity. Answer (b) is the most biochemically precise.
Q26 - Exercise energy metabolism
26(i) First 5-10 seconds of high-intensity explosive exercise: d) Phosphagen system
The phosphagen system (ATP-PCr system / creatine phosphate system) provides immediate ATP for the first 5-10 seconds of maximal explosive activity (sprinting, weightlifting) without requiring oxygen. Anaerobic glycolysis takes over from ~10 seconds to 2 minutes.
26(ii) Crossover Concept - fuel shift as exercise intensity increases: b) From predominantly fats to predominantly carbohydrates
The Crossover Concept states that at low exercise intensities, fat oxidation predominates. As intensity increases, there is a "crossover" to greater reliance on carbohydrates (glucose/glycogen). High-intensity exercise exceeds the capacity of fat oxidation and relies on rapid glycolysis.
Q27 - 10-day-old infant: Jaundice, cataracts, hepatomegaly, aminoaciduria, symptoms worsen with milk
27(i) Enzyme deficiency: b) Galactose-1-phosphate uridyltransferase (GALT)
Per Robbins & Kumar: "Galactosemia is an autosomal recessive disorder of galactose metabolism resulting from a mutation in the gene encoding the enzyme galactose-1-phosphate uridyltransferase (GALT)." Symptoms worsen with milk (lactose = glucose + galactose). Classic features: jaundice, cataracts, hepatomegaly, E. coli sepsis, aminoaciduria. Galactokinase deficiency only causes cataracts.
27(ii) Direct cause of cataract formation: c) Accumulation of Galactitol
Per Biochemistry Lippincott: "Excess galactose is converted to galactitol by aldose reductase. This causes liver damage, brain damage, and cataracts." Galactitol accumulates in the lens (it cannot be further metabolized), draws in water by osmosis, and causes cataract formation. Galactose-1-phosphate is responsible for liver/brain toxicity.
Summary Table
| Q | Part | Answer |
|---|---|---|
| 18 | (i) | c) Acute Intermittent Porphyria |
| 18 | (ii) | d) Uroporphyrinogen I synthase |
| 19 | (i) | c) Xeroderma Pigmentosum |
| 19 | (ii) | d) Nucleotide excision repair |
| 20 | (i) | b) Increases permeability of inner mitochondrial membrane to protons |
| 20 | (ii) | c) Decreases proton motive force and decreases ATP yield |
| 21 | (i) | c) Hyperphagia, obesity |
| 21 | (ii) | b) High leptin levels with leptin resistance |
| 22 | (i) | c) Inhibition of Cytochrome oxidase |
| 22 | (ii) | c) Acting as a potassium ionophore, dissipating membrane potential |
| 23 | (i) | b) Chronic endothelial cell injury |
| 23 | (ii) | c) Oxidation |
| 24 | (i) | d) Ornithine transcarbamylase |
| 24 | (ii) | a) Accumulation of carbamoyl phosphate leaking into cytosol |
| 25 | (i) | c) Increased glucagon/insulin ratio - increased lipolysis |
| 25 | (ii) | b) Lack of thiophorase (succinyl-CoA transferase) in liver |
| 26 | (i) | d) Phosphagen system |
| 26 | (ii) | b) From fats to carbohydrates |
| 27 | (i) | b) Galactose-1-phosphate uridyltransferase |
| 27 | (ii) | c) Accumulation of Galactitol |
Reading File
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Finding Sources
I have enough library support. Here is the complete answer key with full explanations:
Complete Answer Key - Biochemistry MCQs (Set 2)
Q18 - Infant with milky lipemic plasma, elevated VLDL and chylomicrons, normal LDL
18(i) Underlying cause: d) Chylomicrons
In the fasting state, normal LDL with elevated triglycerides and a milky plasma appearance points to persistence of chylomicrons - which should be cleared after fasting. This is Familial Lipoprotein Lipase (LPL) deficiency (Type I hyperlipoproteinemia). Chylomicrons are the main particle responsible for the milky/creamy plasma appearance. VLDL would be elevated too, but the primary cause of the milky appearance is chylomicrons.
18(ii) Lipoprotein particle primarily responsible for milky appearance: d) Chylomicrons
Chylomicrons are the largest and lightest lipoproteins, rich in dietary triglycerides. Their accumulation turns plasma creamy/milky (lactescent). LDL is normal in LPL deficiency because it is derived downstream.
18(i) Enzyme or cofactor deficiency: c) Hepatic Lipase / LPL
The correct answer from the options is: b) Lipoprotein Lipase (LPL) - LPL is the enzyme that hydrolyzes triglycerides in chylomicrons and VLDL at the capillary endothelium. Its deficiency causes massive hypertriglyceridemia. ApoC-II (option d) is the cofactor/activator of LPL - its deficiency also causes the same picture.
From the options given:
- 18(i) underlying cause of milky plasma: d) Chylomicrons
- 18(ii) lipoprotein responsible for milky appearance: d) Chylomicrons
- The deficiency enzyme/cofactor: both LPL and ApoC-II are correct. From the choices - b) Lipoprotein Lipase (LPL) is the enzyme; d) its activator ApoC-II is the cofactor. The question asks which enzyme/cofactor - answer is b) LPL as the enzyme, or d) ApoC-II as the activator/cofactor. Since the question specifically says "enzyme or cofactor," if it's asking about CETP (cholesteryl ester transfer protein) - that is not involved here. Answer: b) Lipoprotein Lipase (LPL) for enzyme deficiency.
Q19 - Rotenone experiment on isolated mitochondria
19(i) Primary functional effect of rotenone on electron flow and proton gradient:
b) Electron transfer from NADH to Coenzyme Q is halted, causing a drop in proton-motive force
Rotenone is a specific inhibitor of Complex I (NADH:ubiquinone oxidoreductase). It blocks the transfer of electrons from NADH to Coenzyme Q (ubiquinone). Since Complex I is the entry point for NADH electrons and pumps 4 H⁺ per 2 electrons, its inhibition reduces proton pumping and lowers the proton-motive force.
- Option (a): electrons do NOT flow backward to reduce O₂ directly - that's not the mechanism
- Option (c): electrons do NOT jump from Complex I to Complex III - they go NADH→CoQ→Complex III→Cyt c→Complex IV
- Option (d): pH of the matrix would become MORE acidic relative to the IMS collapse scenario, not highly alkaline
19(ii) If succinate is added when Complex I is entirely destroyed - expected outcome:
c) The entire ETC pathway will be rescued and ATP synthesis will resume because electrons from succinate enter the ETC
Succinate enters at Complex II (Succinate Dehydrogenase) which directly reduces CoQ. Complex II bypasses Complex I entirely. So if Complex I is destroyed, succinate can still feed electrons to CoQ → Complex III → Cyt c → Complex IV → O₂, restoring ATP synthesis (though at reduced efficiency since Complex I normally contributes ~40% of the proton gradient).
- Option (a) is wrong - no electron transport will NOT occur; succinate provides an alternative entry point
- Option (b) - ATP synthesis will be rescued, not at 100% because Complex I is gone, but it WILL resume
- The best answer is c) - ETC will resume via the succinate/Complex II pathway
Q20 - 50-year-old man: Bronze skin pigmentation, diabetes mellitus, liver cirrhosis
20(i) Mineral involved: b) Iron
The triad of bronze skin + diabetes mellitus + liver cirrhosis = Hemochromatosis (iron overload). Excess iron deposits in skin (bronze discoloration due to hemosiderin + increased melanin), pancreas (diabetes), and liver (cirrhosis). This is the classic "bronze diabetes."
- Copper causes Wilson disease (Kayser-Fleischer rings, liver + neuro)
- Selenium deficiency causes Keshan disease (cardiomyopathy)
- Zinc deficiency causes acrodermatitis enteropathica
20(ii) Hormone that regulates absorption of the mineral: a) Hepcidin
Hepcidin is the master regulator of iron homeostasis. It is a peptide hormone produced by the liver that:
- Binds to ferroportin (the iron exporter on enterocytes and macrophages)
- Causes ferroportin internalization and degradation
- Reduces iron absorption from the gut and iron release from stores
In hereditary hemochromatosis, hepcidin is deficient/non-functional, leading to unregulated iron absorption.
Q21 - Glycogen Phosphorylase activation in liver in response to glucagon
21(i) How Glycogen Phosphorylase is abruptly activated (cascade): c) By proteolytic cleavage of the zymogen
Wait - Glycogen Phosphorylase is NOT a zymogen. It is activated by covalent modification (phosphorylation), not proteolytic cleavage. The correct cascade is:
- Glucagon → Gs-coupled receptor → adenylate cyclase → cAMP ↑ → PKA activation → Phosphorylase kinase phosphorylation → Glycogen Phosphorylase b phosphorylated → Glycogen Phosphorylase a (active)
So the answer is d) By the binding of a phosphate group (covalent modification - phosphorylation by phosphorylase kinase)
21(ii) Regulatory mechanism described (enzyme activated by covalent phosphate attachment) is known as:
c) Covalent modification
The activation of glycogen phosphorylase by phosphorylation is the classic example of covalent modification (specifically, phosphorylation at a serine residue by phosphorylase kinase). This converts the less active "b" form to the highly active "a" form.
- Allosteric regulation: binding of non-covalent effectors (AMP, ATP, glucose-6-phosphate)
- Feedback inhibition: product inhibits the pathway
- Isozyme conversion: different gene products
Q22 - Marathon runner using lipids in later stages of a race
22(i) Primary lipid storage in human adipose tissue: b) Triacylglycerols (Triglycerides)
Adipose tissue stores lipids almost exclusively as triacylglycerols (TAGs) - esters of glycerol with three fatty acid chains. Phospholipids are structural membrane components. Free fatty acids and cholesterol esters are present in small amounts but are not the primary storage form.
22(ii) Enzyme responsible for hydrolysis of stored triglycerides in adipocytes during exercise:
d) Hormone-sensitive lipase (HSL)
During exercise (especially prolonged endurance like a marathon), catecholamines and glucagon activate adenylate cyclase → PKA → Hormone-Sensitive Lipase (HSL) is phosphorylated and activated. HSL hydrolyzes stored triglycerides in adipocytes into free fatty acids + glycerol. These FAs are released into the blood bound to albumin and taken up by muscle for beta-oxidation.
- Lipoprotein lipase hydrolyzes triglycerides in circulating lipoproteins (chylomicrons, VLDL) at capillary endothelium - NOT stored TAGs
- Pancreatic lipase digests dietary fats in the intestine
Q23 - Patient given 0.45% Hypotonic Saline instead of 0.9% Normal Saline
23(i) Physiological change in red blood cells:
b) Water will move into the cells, causing them to swell and potentially lyse
0.45% NaCl is hypotonic relative to normal extracellular fluid (~0.9% / ~310 mOsm). When RBCs are placed in a hypotonic environment, osmotic pressure drives water INTO the cells (down the osmotic gradient from dilute solution outside → concentrated cell interior). This causes RBCs to swell → can progress to hemolysis (lysis = rupture = osmotic hemolysis).
23(ii) Membrane transport mechanism for water crossing the RBC membrane:
c) Simple diffusion directly through the lipid bilayer and via aquaporins
Water crosses cell membranes by:
- Aquaporins (AQP1 in RBCs) - protein channels highly specific for water - this is the primary, fast route
- Simple diffusion through lipid bilayer - minor contribution
The question asks which mechanism - the best answer is c) Simple diffusion directly through the lipid bilayer and via aquaporins. (Note: Some options might list "facilitated diffusion via aquaporins" alone - that is also acceptable. Aquaporin-mediated transport is technically "facilitated diffusion." Option b - facilitated diffusion via aquaporins - could also be correct depending on framing.)
Q24 - 7-year-old child: Chronic cholestatic liver disease, gait instability, loss of vibration sense, muscle weakness, lipid peroxidation of RBC membranes
24(i) Primary biochemical process that has failed:
c) Free radical scavenging in lipid membranes
The clinical picture - neurological degeneration (ataxia, loss of vibration sense), muscle weakness, and lipid peroxidation of erythrocyte membranes in a child with cholestatic liver disease = Vitamin E (tocopherol) deficiency.
Vitamin E is a fat-soluble vitamin absorbed with dietary fat (requires bile). Chronic cholestatic liver disease reduces bile flow → fat malabsorption → fat-soluble vitamin deficiency (A, D, E, K). Vitamin E's primary function is as a lipid-soluble antioxidant that scavenges free radicals in cell membranes, protecting polyunsaturated fatty acids from peroxidation.
- Hydroxylation of proline = Vitamin C (scurvy) - causes collagen defects
- γ-Carboxylation of glutamate = Vitamin K - causes coagulation defects
- Oxidative deamination of amino acids = not a deficiency disease mechanism here
24(ii) Cellular component most susceptible to damage:
b) Cell membrane polyunsaturated fatty acids (PUFAs)
Vitamin E deficiency leads to unchecked lipid peroxidation chain reactions in cell membranes. The primary targets are the polyunsaturated fatty acids (PUFAs) in phospholipid bilayers, especially those with multiple double bonds (arachidonic acid, DHA, EPA). Free radical chain reactions propagate through PUFA side chains, disrupting membrane integrity.
Q25 - 17-year-old girl: Angular stomatitis, glossitis, seborrheic dermatitis, corneal vascularization; poor intake of milk and dairy
25(i) Metabolic pathway most directly affected:
a) Oxidation-reduction reactions involving flavoproteins
The symptoms - angular stomatitis (cracks at mouth corners), glossitis (inflamed tongue), seborrheic dermatitis, corneal vascularization - are classic features of Vitamin B2 (Riboflavin) deficiency. Riboflavin is found abundantly in milk and dairy products.
Riboflavin is the precursor for FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide), which are essential cofactors (prosthetic groups) for flavoproteins involved in oxidation-reduction reactions throughout metabolism (Complex I, Complex II of ETC, fatty acid oxidation, amino acid metabolism, etc.).
25(ii) Enzyme activity most likely to be impaired:
b) FAD (Flavin Adenine Dinucleotide)
Riboflavin deficiency impairs all FAD- and FMN-dependent enzymes. From the choices:
- NADPH - cofactor of many reductases (riboflavin is not its precursor)
- FAD - directly derived from riboflavin. All FAD-dependent enzymes (succinate dehydrogenase, acyl-CoA dehydrogenase, etc.) are impaired
- Coenzyme A - derived from pantothenate (Vit B5)
- Biotin - separate vitamin
Answer: b) FAD
Q26 - Carbohydrates and isomerism: D-Glucose and D-Galactose
26(i) Correct relationship between D-Glucose and D-Galactose:
d) C-4 Epimers
D-Glucose and D-Galactose differ ONLY at Carbon-4 (the -OH group is axial in galactose vs equatorial in glucose). Compounds that differ at only ONE chiral carbon are called epimers. Since they differ at C-4, they are C-4 epimers. They are NOT enantiomers (mirror images would require ALL stereocenters to be reversed).
26(ii) True about anomers EXCEPT:
d) In mutarotation, Dextrorotatory sugar is converted to levo rotatory
Anomers are:
- (a) TRUE: Formed due to cyclization of linear carbohydrates (ring closure creates a new chiral center at C-1 = anomeric carbon) ✓
- (b) TRUE: Due to formation of a new asymmetric carbon (C-1 becomes chiral) ✓
- (c) TRUE: Mutarotation is a property of anomers (interconversion of α and β forms in solution) ✓
- (d) FALSE: In mutarotation, the optical rotation reaches an equilibrium value between α and β forms. It is NOT simply "dextrorotatory converting to levo." For glucose: α-D-glucose (+112.2°) and β-D-glucose (+18.7°) both reach equilibrium at +52.7° - both are dextrorotatory. The statement in (d) is incorrect/oversimplified.
Answer: d) is FALSE (the exception)
Q27 - 14-year-old boy: Generalized weakness, epileptic seizures, abdominal pain, hepatomegaly, Kayser-Fleischer rings
27(i) Biochemical defect:
c) Decreased copper binding protein (Ceruloplasmin)
The Kayser-Fleischer rings (copper deposits in Descemet's membrane of cornea) + hepatomegaly + neurological symptoms (seizures, weakness) = Wilson's Disease (Hepatolenticular Degeneration).
Wilson's disease is caused by a defect in the ATP7B gene (copper-transporting ATPase) → copper cannot be incorporated into ceruloplasmin or excreted into bile → copper accumulates in liver, brain, cornea, kidneys.
The biochemical hallmark: decreased serum ceruloplasmin (the copper-binding protein) because copper cannot be incorporated into it properly, so it is rapidly degraded.
- Dietary copper intake is normal (not decreased)
- Absorption is normal (not decreased)
- Excretion is actually DECREASED (copper is retained, not excreted more)
27(ii) Penicillamine acts by:
d) Increasing excretion of copper
Penicillamine (D-penicillamine) is a copper chelator. It binds free copper in tissues and plasma, forming a soluble complex that is excreted in the urine. This is how it removes excess copper from the body. It does NOT:
- Increase copper absorption (that would worsen the disease)
- Increase binding to ceruloplasmin
- Increase copper transport
Answer: d) Increasing excretion of copper
Summary Table
| Q | Part | Answer |
|---|---|---|
| 18 | (i) Deficient enzyme/cofactor | b) Lipoprotein Lipase (LPL) |
| 18 | (ii) Lipoprotein causing milky plasma | d) Chylomicrons |
| 19 | (i) Rotenone effect | b) Electron transfer NADH→CoQ halted, proton-motive force drops |
| 19 | (ii) Succinate added - outcome | c) ETC rescued, ATP synthesis resumes via Complex II |
| 20 | (i) Mineral in bronze skin + DM + cirrhosis | b) Iron (Hemochromatosis) |
| 20 | (ii) Hormone regulating iron absorption | a) Hepcidin |
| 21 | (i) Glycogen Phosphorylase activation | d) Covalent modification (phosphorylation) |
| 21 | (ii) Name of regulatory mechanism | c) Covalent modification |
| 22 | (i) Primary lipid storage in adipose | b) Triacylglycerols |
| 22 | (ii) Enzyme hydrolyzing stored TAGs | d) Hormone-sensitive lipase |
| 23 | (i) RBC response to hypotonic saline | b) Water moves in → cells swell and lyse |
| 23 | (ii) Water transport mechanism | c) Simple diffusion + aquaporins (or b: facilitated via aquaporins) |
| 24 | (i) Biochemical process failed | c) Free radical scavenging (Vitamin E deficiency) |
| 24 | (ii) Most susceptible cellular component | b) Cell membrane polyunsaturated fatty acids |
| 25 | (i) Pathway most affected (riboflavin deficiency) | a) Oxidation-reduction via flavoproteins |
| 25 | (ii) Enzyme cofactor impaired | b) FAD |
| 26 | (i) D-Glucose vs D-Galactose relationship | d) C-4 Epimers |
| 26 | (ii) False statement about anomers | d) Mutarotation converts dextro to levo |
| 27 | (i) Wilson disease - biochemical defect | c) Decreased copper binding protein (ceruloplasmin) |
| 27 | (ii) Penicillamine mechanism | d) Increasing excretion of copper |
This is a shared conversation. Sign in to Orris to start your own chat.