Lipid Metabolism Practice Questions

Q: Rothera's test is used for detection of:

Ketones. ***Ketones*** - **Rothera's test** is a qualitative test used to detect the presence of **ketone bodies**, primarily **acetoacetate and acetone**, in urine. - A positive test typically indicates **ketosis**, which can occur in conditions like **diabetic ketoacidosis** or prolonged fasting. *Proteins* - **Proteins** in urine are typically detected using tests such as the **sulfosalicylic acid (SSA) test** or **urine dipstick protein tests**. - **Rothera's test** does not react with proteins. *Fatty acid* - **Fatty acids** in urine are not routinely tested for specific detection with a single spot test like **Rothera's test**. - **Rothera's test** is specific for ketone bodies, not fatty acids. *Glucose* - **Glucose** in urine is commonly detected using **urine dipstick tests** which rely on the **glucose oxidase enzymatic reaction**. - **Rothera's test** does not detect glucose.

Q: A female child presents with hypertension, hyperpigmentation and virilization, she is most likely to be suffering from deficiency of?

11 beta hydroxylase deficiency. ***11 beta hydroxylase deficiency*** - This deficiency leads to an accumulation of **11-deoxycorticosterone (DOC)**, a potent mineralocorticoid that causes **hypertension**. [1] - The excess adrenal androgens (due to shunting of precursors down the androgen pathway) cause **virilization** and **hyperpigmentation** from increased ACTH stimulating melanocortin receptors. [1] *3 beta hydroxylase* - This deficiency causes a severe form of **congenital adrenal hyperplasia (CAH)** with impaired synthesis of all adrenal steroids. [1] - It presents with **salt wasting** and **ambiguous genitalia** in females due to lack of cortisol, aldosterone, and sex steroids. *21 alpha hydroxylase* - The most common form of CAH, resulting in decreased **cortisol** and **aldosterone**, and increased adrenal androgens. - It presents with **salt wasting** or **virilization** (depending on severity), but typically **hypotension** rather than hypertension. *17 alpha hydroxylase* - This deficiency impairs the synthesis of **cortisol** and **androgens**, leading to an accumulation of **mineralocorticoid precursors** like DOC. - Patients present with **hypertension**, **hypokalemia**, and **sexual infantilism** (lack of pubertal development) rather than virilization.

Q: Which of the following is a 17β-OH steroid?

Androgen. ***Androgen*** - **Testosterone** is the classic example of a **17β-hydroxysteroid**, containing a hydroxyl group (-OH) at the **17β-position** of its steroid nucleus. - Other androgens like **androstenediol** and **dehydroepiandrosterone (DHEA)** derivatives also possess the **17β-OH configuration**. - This structural feature is essential for **androgen receptor binding** and biological activity in target tissues. - The 17β-hydroxyl group distinguishes active androgens from their inactive 17-ketosteroid metabolites. *Estrogen* - **Estradiol**, the primary estrogen, also contains a **17β-hydroxyl group**, making it technically a 17β-OH steroid. - However, in the context of steroid chemistry and clinical biochemistry, **testosterone** (androgen) is more commonly referenced as the prototypical **17β-hydroxysteroid**. - Both androgens and estrogens can be 17β-OH steroids, but androgens are the primary class associated with this terminology in medical literature. *Progesterone* - **Progesterone** is a C21 steroid with a **ketone group at C3 and C20**, not a hydroxyl group. - At position 17, progesterone has an **acetyl side chain** (CH3CO-), not a hydroxyl group. - It lacks the 17β-OH configuration that characterizes androgenic and estrogenic steroids. *None of the options* - This is incorrect because **androgen** (specifically testosterone) is a well-established **17β-hydroxysteroid**. - The measurement of **17-ketosteroids** (oxidized metabolites of 17β-OH steroids) in urine was historically used to assess androgen production.

Q: Which of the following is caused by congenital 17 hydroxylase deficiency:

Hypertension. ***Hypertension*** - **Congenital 17-hydroxylase deficiency** leads to impaired synthesis of **cortisol** and **sex steroids**, resulting in an accumulation of **mineralocorticoid precursors (corticosterone and deoxycorticosterone)** [1]. - Increased levels of these mineralocorticoids cause **sodium and water retention**, leading to **hypertension** and **hypokalemia**. *Virilism* - **17-hydroxylase deficiency** impairs **androgen synthesis**, preventing the development of male secondary sexual characteristics [2]. - Individuals with this deficiency often present with **female external genitalia** regardless of their genetic sex, or **under-virilization** in genetic males, not virilism [2]. *Hyperkalemia* - The excess mineralocorticoids (deoxycorticosterone) in **17-hydroxylase deficiency** promote **sodium reabsorption** and **potassium excretion** in the kidneys [1]. - This leads to **hypokalemia**, which is the opposite of hyperkalemia. *Hermaphroditism* - **17-hydroxylase deficiency** affects the development of gonads and internal reproductive organs depending on genetic sex. - Genetic males (**XY**) with this deficiency typically develop **female external genitalia** (pseudohermaphroditism or 46, XY DSD), while genetic females (**XX**) typically present as normal females but with **primary amenorrhea** [2]. This genetic condition does not result in true hermaphroditism (presence of both ovarian and testicular tissue) [2].

Q: Bile salts undergo conjugation for enhanced solubility:

After conjugation with taurine and glycine. ***After conjugation with taurine and glycine*** - This statement accurately describes the most common conjugation pathway for bile acids, increasing their **amphipathic properties** and solubility. - Conjugation with these amino acids forms **bile salts** (e.g., glycocholate, taurocholate), which are essential for **micelle formation** and fat digestion. - This is the primary mechanism by which bile acids become bile salts with enhanced solubility. *After conjugation with betaglucuronic acid* - While bile acids do undergo conjugation for increased solubility, they are primarily conjugated with glycine or taurine, not beta-glucuronic acid. - Conjugation with beta-glucuronic acid is a common detoxification pathway for many xenobiotics and bilirubin, but not the primary method for bile acids. *After conjugation with derived proteins* - Bile salts are primarily steroid derivatives and are not conjugated with derived proteins. - The purpose of conjugation is to increase hydrophilicity, which proteins would not achieve in this context. *After conjugation with lysine* - Lysine is an amino acid but is not involved in the conjugation of bile acids. - Bile acid conjugation specifically uses the amino acids glycine and taurine.

Q: Active metabolite in the synthesis of fatty acids is:

Malonyl CoA. ***Malonyl CoA*** - **Malonyl CoA** is the immediate **two-carbon donor** in fatty acid synthesis, formed from acetyl CoA and bicarbonate. - It adds **two-carbon units** to the growing fatty acid chain during each cycle of synthesis, making it the primary active metabolic form in this process. *Stearate (an end product of fatty acid synthesis)* - **Stearate** is a **saturated fatty acid end product** (C18:0) of fatty acid synthesis, not an active metabolite that directly participates in the elongation process. - While it is a result of fatty acid synthesis, it does not serve as a building block for further elongation in the manner of malonyl CoA. *Acetyl CoA (a precursor in fatty acid synthesis)* - **Acetyl CoA** is the **initial precursor** for fatty acid synthesis, which is then carboxylated to form malonyl CoA. - It is not the *active* two-carbon donor during the elongation steps of fatty acid synthesis itself, but rather the substrate for malonyl CoA synthesis. *Palmitate (an end product of fatty acid synthesis)* - **Palmitate** is the **primary 16-carbon saturated fatty acid** and is the usual end product of *de novo* fatty acid synthesis in humans. - Like stearate, it is an end product and does not serve as an active metabolic intermediate for chain elongation during the synthesis process itself.

Q: Which apolipoprotein is most strongly associated with increased risk of Alzheimer's disease?

APOE4. APOE4 - The APOE4 allele is the strongest genetic risk factor for late-onset Alzheimer's disease, increasing risk and lowering the age of onset in a gene-dose dependent manner. - Individuals with one copy of APOE4 have a 2-3 times increased risk, and those with two copies have an 8-12 times increased risk compared to those with APOE3. APOE3 - APOE3 is the most common allele and is considered a neutral risk factor for Alzheimer's disease. - It plays a normal role in lipid metabolism and brain function without significantly increasing or decreasing AD risk. APOC3 - APOC3 is involved in triglyceride metabolism and is primarily linked to cardiovascular disease risk, not Alzheimer's disease. - While it modulates lipid levels, it does not have a direct, strong genetic association with AD pathogenesis. APOE2 - APOE2 is associated with a reduced risk of Alzheimer's disease, offering a protective effect against its development. - It is thought to improve the clearance of amyloid-beta (A̠) plaques, a hallmark of AD pathology.

Q: In a preterm baby with respiratory distress syndrome, which of the following lipids would be deficient?

Lecithin. ***Lecithin*** - **Lecithin** (also known as **phosphatidylcholine**) is the primary component of **surfactant** in the lungs, which reduces surface tension and prevents alveolar collapse. - In **preterm babies**, insufficient production of lecithin due to immature lung development leads to **respiratory distress syndrome (RDS)**. *Cardiolipin* - **Cardiolipin** is a major phospholipid found in the **inner mitochondrial membrane**, crucial for oxidative phosphorylation. - Deficiency is associated with mitochondrial disorders like **Barth syndrome**, not primary respiratory distress. *Sphingomyelin* - **Sphingomyelin** is a significant component of **cell membranes** and **myelin sheaths**, important for nerve insulation. - While present in the lungs, its primary role is not in surface tension reduction, and its deficiency is not directly linked to RDS. *Phosphatidylinositol* - **Phosphatidylinositol** is a precursor for various **signaling molecules** and plays a role in cell membrane structure. - While involved in cellular processes, it is not the critical surfactant component whose deficiency causes RDS.

Q: Type-I hyperlipoproteinemia is caused by deficiency of:-

Lipoprotein lipase. ***Lipoprotein lipase*** - **Type I hyperlipoproteinemia**, also known as **familial lipoprotein lipase deficiency**, is caused by a genetic defect leading to **deficiency or defect in lipoprotein lipase (LPL)** or its cofactor **apolipoprotein C-II**. - LPL is crucial for the **hydrolysis of triglycerides** in chylomicrons and VLDL at the capillary endothelium. - This enzymatic deficiency leads to **massive accumulation of chylomicrons** and severe hypertriglyceridemia (often >1000 mg/dL). - Clinical features include **eruptive xanthomas, lipemia retinalis, hepatosplenomegaly**, and **recurrent pancreatitis**. *Elevated triglycerides in plasma* - This is indeed the **most prominent laboratory finding** in Type I hyperlipoproteinemia, with triglyceride levels often exceeding 1000-2000 mg/dL. - However, this is the **consequence/manifestation** of the LPL deficiency, not the underlying cause. - The question asks what causes Type I hyperlipoproteinemia, which is the enzyme deficiency itself. *Elevated LDL* - Type I hyperlipoproteinemia typically has **normal or even reduced LDL levels**. - **Elevated LDL** is characteristic of **Type IIa hyperlipoproteinemia (familial hypercholesterolemia)**, which involves defects in LDL receptor or ApoB-100. - Type I primarily affects **chylomicron metabolism**, not LDL. *Elevated cholesterol* - Cholesterol levels are typically **normal or only mildly elevated** in Type I hyperlipoproteinemia. - The triglyceride elevation is disproportionately massive compared to any cholesterol elevation. - Significant isolated cholesterol elevation points to Type IIa or IIb dyslipidemias.

Q: Retinitis pigmentosa is associated with deficiency of:

DHA. ***DHA*** - **Docosahexaenoic acid (DHA)** is the major polyunsaturated fatty acid in the **retinal photoreceptor outer segments** and is crucial for their function. - Deficiency in DHA has been linked to several retinal degeneration disorders, including **retinitis pigmentosa**, suggesting its importance in maintaining retinal health. *Timnodonic acid* - This is an older term for **eicosapentaenoic acid (EPA)**, which is an omega-3 fatty acid. - While EPA is beneficial for overall health, it is **not the primary fatty acid** associated with the direct structural and functional health of retinal photoreceptors as DHA is. *Eicosa pentaenoic acid* - **Eicosapentaenoic acid (EPA)** is an omega-3 fatty acid found in fish oil, known for its anti-inflammatory properties. - While important for general health, EPA is **not as abundant or critical for retinal structure and function** as DHA. *Arachidonic acid* - **Arachidonic acid (AA)** is an omega-6 fatty acid found in cell membranes and is a precursor to pro-inflammatory mediators. - While present in the retina, AA is generally **not associated with a protective or causative role in retinitis pigmentosa** in the same way DHA is.

Question 1

Rothera's test is used for detection of:

Accepted Answer

Ketones

Answer

Proteins

Answer

Fatty acid

Answer

Glucose

Question 2

A female child presents with hypertension, hyperpigmentation and virilization, she is most likely to be suffering from deficiency of?

Accepted Answer

11 beta hydroxylase deficiency

Answer

3 beta hydroxylase

Answer

21 alpha hydroxylase

Answer

17 alpha hydroxylase

Question 3

Which of the following is a 17β-OH steroid?

Accepted Answer

Androgen

Answer

Estrogen

Answer

Progesterone

Answer

None of the options

Question 4

Which of the following is caused by congenital 17 hydroxylase deficiency:

Accepted Answer

Hypertension

Answer

Virilism

Answer

Hyperkalemia

Answer

Hermaphroditism

Question 5

Bile salts undergo conjugation for enhanced solubility:

Accepted Answer

After conjugation with taurine and glycine

Answer

After conjugation with derived proteins

Answer

After conjugation with lysine

Answer

After conjugation with betaglucuronic acid

Question 6

Active metabolite in the synthesis of fatty acids is:

Accepted Answer

Malonyl CoA

Answer

Stearate

Answer

Acetyl CoA

Answer

Palmitate

Question 7

Which apolipoprotein is most strongly associated with increased risk of Alzheimer's disease?

Accepted Answer

APOE4

Answer

APOE3

Answer

APOC3

Answer

APOE2

Question 8

In a preterm baby with respiratory distress syndrome, which of the following lipids would be deficient?

Accepted Answer

Lecithin

Answer

Cardiolipin

Answer

Sphingomyelin

Answer

Phosphatidylinositol

Question 9

Type-I hyperlipoproteinemia is caused by deficiency of:-

Accepted Answer

Lipoprotein lipase

Answer

Elevated triglycerides in plasma

Answer

Elevated LDL

Answer

Elevated cholesterol

Question 10

Retinitis pigmentosa is associated with deficiency of:

Accepted Answer

DHA

Answer

Timnodonic acid

Answer

Eicosa pentaenoic acid

Answer

Arachidonic acid

Lipid Metabolism — MCQs

Lipid Metabolism — MCQs

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