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Gastrointestinal and Nutrition Physiology

Energy metabolism Practice Questions

38 free Energy metabolism practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

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Question 1 of 38 Medium

The preferred energy source for colonic epithelial cells (colonocytes) is:

  1. A Glucose
  2. B Fatty acids from the diet
  3. C Circulating amino acids
  4. D Short-chain fatty acids

Correct answer: Short-chain fatty acids

Colonocytes preferentially oxidize short-chain fatty acids, especially butyrate, as their main fuel. These are produced by bacterial fermentation of dietary fiber.

Question 2 of 38 Medium

Which macronutrient provides the highest energy yield per gram?

  1. A Carbohydrates
  2. B Proteins
  3. C Fats
  4. D Alcohol

Correct answer: Fats

Fats provide approximately 9 kcal per gram, which is more than carbohydrates or proteins. This high energy density reflects their reduced chemical state.

Question 3 of 38 Medium

After a carbohydrate-rich meal, the primary hormone promoting energy storage is:

  1. A Glucagon
  2. B Insulin
  3. C Cortisol
  4. D Epinephrine

Correct answer: Insulin

Insulin is released in response to elevated blood glucose after meals. It promotes glucose uptake and storage as glycogen and fat.

Question 4 of 38 Medium

The main pathway responsible for ATP generation from glucose in enterocytes is:

  1. A Glycolysis
  2. B Gluconeogenesis
  3. C Pentose phosphate pathway
  4. D Urea cycle

Correct answer: Glycolysis

Glycolysis breaks down glucose to generate ATP. It is a primary energy-producing pathway in many cells, including enterocytes.

Question 5 of 38 Medium

Which organ plays a central role in integrating absorbed nutrients for energy metabolism?

  1. A Pancreas
  2. B Liver
  3. C Spleen
  4. D Kidney

Correct answer: Liver

The liver processes absorbed carbohydrates, fats, and proteins. It regulates glycogen storage, lipid synthesis, and amino acid metabolism.

Question 6 of 38 Medium

During fasting, the gastrointestinal tract's contribution to systemic energy balance primarily involves:

  1. A A sharp, sustained increase in insulin secretion
  2. B Enhanced absorption of ingested dietary nutrients
  3. C Mobilizing stored energy via hepatic pathways
  4. D A marked, generalized rise in intestinal motility

Correct answer: Mobilizing stored energy via hepatic pathways

During fasting, the liver maintains blood glucose through glycogenolysis and gluconeogenesis. This supports systemic energy needs.

Question 7 of 38 Medium

Which process converts excess dietary glucose into fatty acids for long-term energy storage?

  1. A Breakdown of stored glycogen
  2. B Breakdown of stored fat (lipolysis)
  3. C De novo lipogenesis
  4. D Oxidation of fat (beta-oxidation)

Correct answer: De novo lipogenesis

De novo lipogenesis converts excess glucose into fatty acids. This occurs primarily in the liver and adipose tissue.

Question 8 of 38 Medium

The primary energy substrate transported from the intestine to the liver after fat digestion is:

  1. A Free fatty acids carried directly in portal blood
  2. B Chylomicron triglycerides via lymphatics
  3. C Ketone bodies
  4. D Glycerol bound to circulating serum albumin

Correct answer: Chylomicron triglycerides via lymphatics

Dietary fats are packaged into chylomicrons and transported via lymphatics. They enter systemic circulation before reaching the liver.

Question 9 of 38 Medium

Which gastrointestinal hormone increases postprandial energy utilization by stimulating insulin release?

  1. A Gastrin
  2. B Secretin
  3. C Cholecystokinin, released after fatty meals
  4. D Glucose-dependent insulinotropic peptide

Correct answer: Glucose-dependent insulinotropic peptide

Glucose-dependent insulinotropic peptide enhances insulin secretion after meals. It links nutrient absorption to energy storage.

Question 10 of 38 Medium

Amino acids absorbed from the intestine are primarily used for energy when:

  1. A Dietary fat intake happens to be high
  2. B Carbohydrate intake remains more than sufficient
  3. C Energy demand outstrips carbohydrate and fat
  4. D Circulating insulin levels are persistently elevated

Correct answer: Energy demand outstrips carbohydrate and fat

Amino acids are used for energy when other fuels are insufficient. They undergo deamination and enter metabolic pathways.

Question 11 of 38 Medium

Which pathway primarily generates ATP from fatty acids absorbed in the intestine?

  1. A Glycolysis
  2. B Beta-oxidation
  3. C Gluconeogenesis
  4. D Cori cycle

Correct answer: Beta-oxidation

Beta-oxidation breaks down fatty acids into acetyl-CoA. This fuels the citric acid cycle and ATP production.

Question 12 of 38 Medium

The postprandial increase in metabolic rate is known as:

  1. A Basal metabolic rate
  2. B Specific dynamic action
  3. C Resting energy expenditure
  4. D Adaptive thermogenesis

Correct answer: Specific dynamic action

Specific dynamic action refers to the increased energy expenditure after eating. It reflects energy costs of digestion and metabolism.

Question 13 of 38 Medium

Which nutrient has the highest thermic effect during digestion and metabolism?

  1. A Carbohydrates
  2. B Fats
  3. C Proteins
  4. D Alcohol

Correct answer: Proteins

Proteins have the highest thermic effect. Their digestion and metabolism require significant energy expenditure.

Question 14 of 38 Medium

Glucose absorbed from the intestine enters the circulation primarily via:

  1. A Lymphatic vessels
  2. B Portal vein
  3. C Hepatic artery
  4. D Inferior vena cava

Correct answer: Portal vein

Glucose enters the portal vein after absorption. It is delivered directly to the liver for metabolic processing.

Question 15 of 38 Medium

Which factor most directly increases intestinal energy absorption efficiency?

  1. A Reduced surface area
  2. B Increased villus height
  3. C Decreased blood flow
  4. D Reduced enzyme activity

Correct answer: Increased villus height

Increased villus height enhances absorptive surface area. This improves nutrient and energy absorption.

Question 16 of 38 Medium

The primary fate of glycerol derived from intestinal fat digestion is:

  1. A Direct oxidation within skeletal muscle
  2. B Conversion to glucose in the liver
  3. C Storage as glycogen inside the intestine
  4. D Excretion unchanged in the urine

Correct answer: Conversion to glucose in the liver

Glycerol is transported to the liver where it can be converted to glucose. This contributes to energy metabolism.

Question 17 of 38 Medium

Which condition most directly impairs gastrointestinal energy absorption?

  1. A Hyperthyroidism
  2. B Short bowel syndrome
  3. C Obesity
  4. D Long-standing hypertension

Correct answer: Short bowel syndrome

Short bowel syndrome reduces absorptive surface area. This limits nutrient and energy uptake.

Question 18 of 38 Medium

During prolonged fasting, the gastrointestinal contribution to energy metabolism shifts toward:

  1. A A sustained rise in intestinal glucose absorption
  2. B Markedly enhanced luminal digestion of dietary fat
  3. C Reduced digestion, relying on hepatic metabolism
  4. D A sustained rise in intestinal protein absorption

Correct answer: Reduced digestion, relying on hepatic metabolism

Prolonged fasting reduces digestive activity. Energy homeostasis relies on hepatic glycogenolysis and gluconeogenesis.

Question 19 of 38 Medium

Which gastrointestinal hormone reduces food intake and influences energy balance by promoting satiety?

  1. A Gastrin, an acid stimulant
  2. B Ghrelin
  3. C Cholecystokinin
  4. D Secretin

Correct answer: Cholecystokinin

Cholecystokinin promotes satiety after meals. It reduces food intake and influences energy balance.

Question 20 of 38 Medium

The primary metabolic role of dietary fiber in energy metabolism is to:

  1. A Provide readily available direct glucose
  2. B Substantially increase dietary fat absorption
  3. C Produce short-chain fatty acids via fermentation
  4. D Directly stimulate pancreatic insulin secretion in the fed state

Correct answer: Produce short-chain fatty acids via fermentation

Dietary fiber is fermented by gut bacteria to short-chain fatty acids. These provide energy to colonocytes and influence systemic metabolism.

Question 21 of 38 Medium

Which organ plays the central role in integrating absorbed nutrients for energy metabolism?

  1. A Pancreas
  2. B Liver
  3. C Kidney
  4. D Colon

Correct answer: Liver

The liver processes absorbed nutrients and regulates their storage, conversion, and release. It is the key organ in maintaining energy homeostasis.

Question 22 of 38 Medium

Amino acids are primarily used for energy under which condition?

  1. A Fed state
  2. B Postprandial state
  3. C Prolonged fasting
  4. D After exercise only

Correct answer: Prolonged fasting

During prolonged fasting, amino acids are used for gluconeogenesis to maintain blood glucose levels. This occurs when carbohydrate reserves are depleted.

Question 23 of 38 Medium

Which hormone primarily promotes energy storage after a carbohydrate-rich meal?

  1. A Glucagon
  2. B Insulin
  3. C Amylin
  4. D Epinephrine

Correct answer: Insulin

Insulin promotes storage of glucose as glycogen and fat. It facilitates uptake of glucose into cells and inhibits breakdown pathways.

Question 24 of 38 Medium

Which macronutrient provides the highest energy per gram?

  1. A Carbohydrates
  2. B Proteins
  3. C Dietary fats
  4. D Vitamins

Correct answer: Dietary fats

Fats provide approximately 9 kcal per gram, which is higher than carbohydrates and proteins (4 kcal/g each).

Question 25 of 38 Medium

Which hormone promotes satiety and reduces food intake?

  1. A Ghrelin
  2. B Leptin
  3. C Orexin
  4. D Motilin

Correct answer: Leptin

Leptin is released from adipose tissue and signals satiety to the hypothalamus. It reduces appetite and regulates energy balance.

Question 26 of 38 Medium

The primary energy source for the enterocytes lining the small intestine is:

  1. A Glucose
  2. B Fatty acids
  3. C Glutamine
  4. D Lactate

Correct answer: Glutamine

Glutamine is the preferred fuel of the enterocyte, taken up from both the gut lumen and the blood, and its carbon skeleton feeds the citric acid cycle to support the rapid turnover of the intestinal lining. Glucose, the intuitive answer, is largely passed on to the rest of the body rather than burnt by these cells, and colonocytes further down the gut are the ones that rely on short-chain fatty acids such as butyrate.

Question 27 of 38 Medium

During prolonged fasting, the gastrointestinal system contributes to energy metabolism mainly by:

  1. A Increasing digestion
  2. B Enhancing nutrient absorption significantly
  3. C Reducing activity and conserving energy
  4. D Increasing hormone secretion

Correct answer: Reducing activity and conserving energy

During fasting, gastrointestinal activity decreases to conserve energy. Nutrient absorption is minimal due to lack of intake.

Question 28 of 38 Medium

After fat digestion, the primary form of lipid transported from the intestine is:

  1. A Free fatty acids
  2. B Cholesterol
  3. C Triglycerides
  4. D Chylomicrons

Correct answer: Chylomicrons

Chylomicrons transport dietary lipids from the intestine through the lymphatic system into the bloodstream.

Question 29 of 38 Medium

Which pathway is the main source of ATP from glucose in enterocytes?

  1. A Lipolysis
  2. B Glycolysis
  3. C Gluconeogenesis
  4. D Pentose phosphate pathway

Correct answer: Glycolysis

Glycolysis is the primary pathway for ATP generation from glucose. It occurs in the cytoplasm of enterocytes.

Question 30 of 38 Medium

What is the primary fate of glycerol derived from triglyceride digestion?

  1. A Stored as fat
  2. B Used for protein synthesis and repair
  3. C Excreted in urine
  4. D Converted to glucose in the liver

Correct answer: Converted to glucose in the liver

Glycerol is transported to the liver and used in gluconeogenesis or glycolysis. It contributes to glucose production.

Question 31 of 38 Medium

Which nutrient has the highest thermic effect during metabolism?

  1. A Carbohydrates
  2. B Fats
  3. C Minerals
  4. D Proteins

Correct answer: Proteins

Proteins have the highest thermic effect due to the energy required for their digestion, absorption, and metabolism.

Question 32 of 38 Medium

Which pathway generates ATP from fatty acids?

  1. A Beta-oxidation
  2. B Glycolysis
  3. C Gluconeogenesis
  4. D Lipogenesis

Correct answer: Beta-oxidation

Beta-oxidation breaks down fatty acids into acetyl-CoA, which enters the Krebs cycle to generate ATP.

Question 33 of 38 Medium

What is the primary metabolic role of dietary fiber?

  1. A Direct ATP production
  2. B Increase dietary fat absorption rate
  3. C Enhance protein digestion
  4. D Produce short-chain fatty acids

Correct answer: Produce short-chain fatty acids

Dietary fiber is fermented by gut bacteria to produce short-chain fatty acids, which can be used as an energy source.

Question 34 of 38 Medium

Which process converts excess glucose into fatty acids for storage?

  1. A Lipogenesis
  2. B Glycogenolysis
  3. C Gluconeogenesis
  4. D Proteolysis

Correct answer: Lipogenesis

Lipogenesis converts excess glucose into fatty acids, which are stored as triglycerides in adipose tissue.

Question 35 of 38 Medium

Which gastrointestinal hormone enhances insulin secretion after a meal?

  1. A Secretin
  2. B GIP
  3. C Motilin
  4. D GLP-1

Correct answer: GLP-1

GLP-1 is an incretin hormone that enhances insulin secretion in response to oral glucose intake.

Question 36 of 38 Medium

During fasting, the primary source of glucose is:

  1. A Glycogen stores and gluconeogenesis
  2. B Dietary intake
  3. C Protein synthesis
  4. D Fat storage in adipose tissue reserves

Correct answer: Glycogen stores and gluconeogenesis

During fasting, glucose is maintained by glycogen breakdown and gluconeogenesis in the liver.

Question 37 of 38 Medium

Which condition most directly impairs nutrient absorption in the intestine?

  1. A Celiac disease
  2. B Hypertension
  3. C Diabetes mellitus
  4. D Hyperthyroidism

Correct answer: Celiac disease

Celiac disease damages the intestinal villi, reducing surface area and impairing nutrient absorption.

Question 38 of 38 Medium

Glucose absorbed from the intestine enters the bloodstream primarily via:

  1. A Portal vein
  2. B Lymphatics
  3. C Thoracic duct
  4. D Systemic arteries

Correct answer: Portal vein

Glucose is transported directly into the portal vein and delivered to the liver for processing.

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