Dietary Fiber and Complex Carbohydrates — MCQs
To reduce mortality by CHD, best strategy -
Which of the following is true regarding nicotine substitution therapy?
History of dislike for sweet food items is typically present in:
All of the following are examples of Dietary fibre except for which of the following?
In a well-fed state, acetyl CoA obtained from diet is least used in the synthesis of
Substance utilized for a barium meal follow-through study is:
What type of carbohydrate is inulin classified as?
Dietary fibres have :
Which is not a dietary fiber ?
Muscle biopsy shows ragged red fibers on modified Gomori trichrome stain. Which enzyme defect is most likely?
Dietary Fiber and Complex Carbohydrates Indian Medical PG Practice Questions and MCQs
Question 1: To reduce mortality by CHD, best strategy -
- A. Secondary prevention
- B. Primordial prevention (Correct Answer)
- C. Tertiary prevention
- D. None of the options
Explanation: ***Primordial prevention*** * This strategy aims to prevent the **development of risk factors** for CHD in the first place, thus preventing the disease itself. * It focuses on promoting healthy lifestyles and environments from early life, targeting populations rather than individuals. *Secondary prevention* * This involves actions taken after an individual has developed **risk factors** for CHD or has been diagnosed with the disease, to prevent recurrence or worsening. * Examples include medication (e.g., statins, antiplatelets) for people with high cholesterol or a history of heart attack. *Tertiary prevention* * This strategy aims to reduce the **impact of an existing disease** on a patient's daily life and prevent further complications, disability, or death. * For CHD, this would include cardiac rehabilitation, surgical interventions like CABG, and managing co-morbidities to improve quality of life and prolong survival. *None of the options* * Given that primordial prevention directly addresses the prevention of risk factors and thus the disease itself, it is the most effective strategy for **reducing overall mortality** at the population level. * Therefore, one of the provided options is indeed the best strategy.
Question 2: Which of the following is true regarding nicotine substitution therapy?
- A. Preferably given by gastrointestinal route.
- B. Varenicline comes with a black box warning of cardiovascular death
- C. There should be a 15-minute gap between nicotine gum and coffee/soda/acidic food as they decrease its absorption (Correct Answer)
- D. Nicotine chewing gum is better for constant use as it gives 25% higher blood level than lozenges
Explanation: ***There should be a 15-minute gap between nicotine gum and coffee/soda/acidic food as they decrease its absorption*** - **Acidic beverages** like coffee, soda, and fruit juices can alter the pH of the mouth and stomach, which significantly **reduces the absorption of nicotine** from gum. - This recommendation ensures optimal **nicotine delivery** and effectiveness of the therapy in reducing withdrawal symptoms. *Preferably given by gastrointestinal route* - Nicotine has poor bioavailability when taken orally due to **extensive first-pass metabolism** in the liver. - Nicotine substitution therapies are therefore preferentially administered via **transdermal**, **buccal** (gum, lozenges), or **nasal routes** to bypass first-pass metabolism and achieve therapeutic blood levels more effectively. *Varenicline comes with a black box warning of cardiovascular death* - Varenicline (Chantix) previously had a black box warning for **neuropsychiatric side effects**, including suicidal ideation and depression, which has since been removed due to further studies. - It does not carry a black box warning specifically for **cardiovascular death**, though cardiovascular events have been a subject of study, particularly in patients with pre-existing cardiovascular conditions. *Nicotine chewing gum is better for constant use as it gives 25% higher blood level than lozenges* - While both nicotine gum and lozenges are effective, the **blood levels achieved are comparable**, and the choice often depends on patient preference and proper technique. - Nicotine gum is best used with a **"chew and park" technique** to allow buccal absorption, and constant chewing can lead to excessive swallowing of nicotine, causing gastrointestinal upset.
Question 3: History of dislike for sweet food items is typically present in:
- A. Glycogen storage disease
- B. Diabetes mellitus
- C. Galactosemia
- D. Hereditary fructose intolerance (Correct Answer)
Explanation: ***Hereditary fructose intolerance*** - Patients with hereditary fructose intolerance develop severe symptoms like **nausea, vomiting, abdominal pain, and hypoglycemia** after ingesting fructose, leading to an aversive response and **dislike for sweet food items**. - This aversion is a protective mechanism, as avoiding fructose-containing foods (including many sweets) prevents the accumulation of toxic metabolites due to a deficiency in **hepatic aldolase B**. *Glycogen storage disease* - While glycogen storage diseases can cause hypoglycemia, they typically do not lead to a specific **aversion to sweet foods**. - The primary defect is in **glycogen synthesis or breakdown**, leading to symptoms like hepatomegaly, muscle weakness, and exercise intolerance. *Diabetes mellitus* - Patients with diabetes mellitus often have a **craving for sweet foods** due to uncontrolled blood glucose levels and insulin resistance, rather than a dislike. - The condition is characterized by **hyperglycemia** and may involve polydipsia, polyuria, and polyphagia. *Galactosemia* - Galactosemia involves an inability to metabolize galactose, leading to symptoms such as **vomiting, lethargy, and jaundice** upon milk ingestion [1]. - While patients will avoid milk, their aversion is not generally to all sweet foods, as sweet foods do not always contain galactose [1].
Question 4: All of the following are examples of Dietary fibre except for which of the following?
- A. Starch (Correct Answer)
- B. Pectin
- C. Lignin
- D. Cellulose
Explanation: ***Correct: Starch*** - **Starch** is a **polysaccharide** that serves as a **storage carbohydrate** in plants and is readily digestible by human enzymes, breaking down into glucose. - While it's a carbohydrate found in plant foods, it does not fit the definition of dietary fibre which is generally resistant to human digestive enzymes. *Incorrect: Pectin* - **Pectin** is a type of **soluble dietary fibre** found in fruits, particularly apples and citrus. - It forms a gel in water, contributing to satiety and helping to **lower cholesterol** and **regulate blood sugar**. *Incorrect: Lignin* - **Lignin** is a **non-carbohydrate dietary fibre** that provides structural support in plants. - It is an **insoluble fibre** and is resistant to breakdown by digestive enzymes, aiding in bulk formation in stool. *Incorrect: Cellulose* - **Cellulose** is a major component of **plant cell walls** and is a type of **insoluble dietary fibre**. - It adds bulk to stool, promoting regularity and preventing constipation.
Question 5: In a well-fed state, acetyl CoA obtained from diet is least used in the synthesis of
- A. Citrate
- B. Acetoacetate (Correct Answer)
- C. Palmitoyl CoA
- D. Oxalosuccinate
Explanation: ***Acetoacetate*** - In a **well-fed state**, the body primarily uses glucose for energy, and acetyl CoA is channeled into fatty acid synthesis rather than **ketone body production** like acetoacetate. - **Acetoacetate** synthesis from acetyl CoA is significantly upregulated during periods of **fasting** or **starvation** to provide an alternative energy source for tissues like the brain. *Citrate* - **Citrate** is formed from acetyl CoA and oxaloacetate in the **citric acid cycle**, which is active in the well-fed state for energy production and providing precursors for biosynthesis. - Additionally, citrate is transported out of the mitochondria into the cytosol to serve as a precursor for **fatty acid synthesis**, consuming acetyl CoA. *Palmitoyl CoA* - **Palmitoyl CoA** is a 16-carbon saturated fatty acid which is synthesized from multiple units of acetyl CoA in the cytosol. - In a **well-fed state**, excess dietary carbohydrates and fats lead to abundant acetyl CoA, which is then readily converted into fatty acids and subsequently stored as **triglycerides**. *Oxalosuccinate* - **Oxalosuccinate** is an intermediate of the **citric acid cycle**, formed from isocitrate. While acetyl CoA is the starting point for the cycle, it is not directly converted into oxalosuccinate. - The citric acid cycle is highly active in the **well-fed state** to generate ATP and provide metabolic intermediates, meaning acetyl CoA is actively consumed within this pathway.
Question 6: Substance utilized for a barium meal follow-through study is:
- A. Barium sulphate (Correct Answer)
- B. Barium oxide
- C. Barium hydroxide
- D. Barium carbonate
Explanation: ***Barium sulphate*** - **Barium sulphate** is the compound used due to its high radiopacacity, allowing for clear visualization of the gastrointestinal tract on X-ray. - It is chemically inert and poorly absorbed in the gastrointestinal tract, minimizing systemic toxicity. *Barium carbonate* - Barium carbonate is **toxic** if ingested, primarily used in industrial applications and ceramics. - It is not suitable for medical imaging due to its solubility and potential for harmful systemic absorption. *Barium oxide* - Barium oxide is a **highly reactive** and corrosive substance, used in industrial applications. - Ingestion would cause severe irritation and chemical burns to the gastrointestinal tract. *Barium hydroxide* - Barium hydroxide is a strong base and is **corrosive**, making it unsuitable for internal consumption. - It can cause severe gastrointestinal irritation and systemic toxicity if ingested.
Question 7: What type of carbohydrate is inulin classified as?
- A. Glucosan
- B. Fructosan (Correct Answer)
- C. Galactosan
- D. Mannosan
Explanation: ***Fructosan*** - **Inulin** is a naturally occurring **polysaccharide** composed primarily of **fructose** units. - As such, it is classified as a **fructosan**, a type of **fructan**, meaning its main monosaccharide component is fructose. *Glucosan* - A **glucosan** is a polysaccharide primarily made up of **glucose** units, such as **starch** or **glycogen**. - Inulin's monomeric units are predominantly fructose, not glucose. *Galactosan* - A **galactosan** is a polysaccharide primarily composed of **galactose** units. - Inulin does not primarily consist of galactose units. *Mannosan* - A **mannosan** is a polysaccharide primarily composed of **mannose** units. - Inulin's structure is based on fructose, not mannose.
Question 8: Dietary fibres have :
- A. catabolic effect
- B. sometimes anabolic and sometimes catabolic effect, depending on the type
- C. anabolic effect
- D. no metabolic effect (Correct Answer)
Explanation: ***no metabolic effect*** - Dietary fibers are **indigestible polysaccharides** that cannot be broken down by human digestive enzymes. - Humans lack enzymes like **cellulase** necessary to hydrolyze the β-glycosidic bonds in dietary fiber. - Dietary fibers pass through the gastrointestinal tract **without being metabolized** by human cells, meaning they do not participate in anabolic or catabolic pathways. - While gut bacteria can ferment some fibers producing short-chain fatty acids (SCFAs), this is **bacterial metabolism**, not human metabolism. - The physiological effects of fiber (improved bowel motility, reduced cholesterol absorption, glycemic control) are **mechanical and physicochemical**, not metabolic. *catabolic effect* - Catabolic processes involve **breakdown of molecules with energy release** (e.g., glycolysis, lipolysis). - Dietary fibers cannot undergo catabolism in humans because we lack the enzymes to break them down. - The fermentation by gut bacteria is not human catabolism. *anabolic effect* - Anabolic processes involve **synthesis of complex molecules** from simpler ones (e.g., protein synthesis, glycogenesis). - Dietary fibers are not absorbed or incorporated into human tissues, so they cannot participate in anabolic reactions. *sometimes anabolic and sometimes catabolic effect, depending on the type* - Regardless of fiber type (soluble or insoluble), **all dietary fibers remain non-metabolizable** by human enzymes. - Neither type undergoes anabolic or catabolic metabolism in human cells.
Question 9: Which is not a dietary fiber ?
- A. Lignin
- B. Pectin
- C. Cellulose
- D. Lactulose (Correct Answer)
Explanation: ***Lactulose*** - **Lactulose is NOT a dietary fiber** - it is a synthetic disaccharide used pharmaceutically as an osmotic laxative and for treating hepatic encephalopathy. - Unlike true dietary fibers, lactulose is a manufactured drug, not a naturally occurring food component. - While it is fermented by colonic bacteria (similar to fiber), it does not meet the definition of dietary fiber. *Lignin* - Lignin is a complex aromatic polymer that provides structural support to plant cell walls. - It is classified as a non-polysaccharide dietary fiber that is largely indigestible by human enzymes. - Contributes to fecal bulk and is considered an insoluble fiber. *Pectin* - Pectin is a soluble dietary fiber found naturally in fruits, particularly in apple peels and citrus fruits. - Forms a gel when mixed with water, slowing gastric emptying and aiding digestion. - Beneficial for gut health and blood glucose regulation. *Cellulose* - Cellulose is the most abundant dietary fiber and a major structural component of plant cell walls. - An insoluble fiber composed of β-1,4-linked glucose polymers that cannot be digested by human enzymes. - Contributes to stool bulk and promotes regular bowel movements.
Question 10: Muscle biopsy shows ragged red fibers on modified Gomori trichrome stain. Which enzyme defect is most likely?
- A. Complex IV
- B. Complex II
- C. Complex III
- D. Complex I (Correct Answer)
Explanation: ***Complex I*** - **Ragged red fibers** on modified Gomori trichrome stain are the pathological hallmark of **mitochondrial myopathies** [1] - **Complex I (NADH-CoQ reductase) deficiency** is the **most common cause** of mitochondrial disease, accounting for approximately 30-40% of all cases - Complex I deficiency is the **most frequent cause of ragged red fibers** in muscle biopsies - Associated clinical features include progressive muscle weakness, exercise intolerance, lactic acidosis, and encephalomyopathy (Leigh syndrome) [1] - The ragged red appearance results from subsarcolemmal accumulation of abnormal mitochondria attempting to compensate for defective oxidative phosphorylation *Complex II* - **Complex II (succinate dehydrogenase) deficiency** is a relatively rare cause of mitochondrial myopathy - More commonly associated with hereditary paraganglioma-pheochromocytoma syndromes and certain cancers - Can cause ragged red fibers but is much less common than Complex I deficiency - The only complex entirely encoded by nuclear DNA (not mitochondrial DNA) *Complex III* - **Complex III (ubiquinol-cytochrome c reductase) deficiency** is a rare cause of mitochondrial disease - Can present with myopathy and ragged red fibers, but accounts for only a small percentage of mitochondrial disorders - Associated with exercise intolerance and multisystem involvement when present *Complex IV* - **Complex IV (cytochrome c oxidase, COX) deficiency** can cause mitochondrial myopathy with ragged red fibers [1] - However, it is **less common than Complex I deficiency** as a cause of ragged red fibers - COX-deficient fibers can be identified using specific COX histochemical staining [1] - Associated with Leigh syndrome and other encephalomyopathies, but not the **most likely** cause when ragged red fibers are present **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1305-1306.
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