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?
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?
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: 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 6: 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 7: 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 8: 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 9: 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.
Question 10: Muscle biopsy shows ragged red fibers on modified Gomori trichrome stain. Which enzyme defect is most likely?
- A. Complex II
- B. Complex I (Correct Answer)
- C. Complex III
- D. Complex IV
Explanation: ***Complex I*** - **Complex I (NADH dehydrogenase) deficiency** is the **most common respiratory chain defect** causing mitochondrial myopathy with ragged red fibers - Accounts for approximately **30-40% of mitochondrial respiratory chain disorders** - **Ragged red fibers** on modified Gomori trichrome stain result from abnormal **subsarcolemmal accumulation of mitochondria** - Clinically presents with **progressive myopathy, exercise intolerance, lactic acidosis**, and may include encephalomyopathy (MELAS syndrome) [1] *Complex IV* - **Complex IV (cytochrome c oxidase/COX) deficiency** is another important cause of mitochondrial myopathy with ragged red fibers - While significant, it is **less common than Complex I deficiency** as a cause of RRF - COX-negative fibers can be identified by specific histochemical staining [1] *Complex III* - **Complex III (ubiquinol-cytochrome c oxidoreductase) deficiency** can cause mitochondrial myopathy - Less frequently associated with prominent ragged red fibers compared to Complex I or IV deficiencies - May present with exercise intolerance and myoglobinuria *Complex II* - **Complex II (succinate dehydrogenase) deficiency** is the rarest cause of mitochondrial myopathy among the respiratory chain complexes - More commonly associated with **paragangliomas and pheochromocytomas** (familial paraganglioma syndromes) - Ragged red fibers are uncommon in isolated Complex II deficiency **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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