multiple choices

Which of the following statements accurately compares the ATP yield from fatty acids and carbohydrates? a) Per gram, carbohydrates produce approximately 2.25 times more ATP than fatty acids. b) Per gram, fatty acids produce approximately 2.25 times less ATP than carbohydrates. c) Per gram, fatty acids produce approximately 2.25 times more ATP than carbohydrates. d) Per gram, the ATP yield from fatty acids and carbohydrates is roughly equivalent. Answer: c)

In the absence of sufficient oxygen, which metabolic pathway allows the body to produce some ATP from glucose? a) Beta-oxidation b) Krebs cycle c) Glycolysis followed by lactic acid fermentation d) Electron transport chain Answer: c)

Which of the following represents the correct order of energy partitioning, starting from the total energy in the diet? a) Gross energy → Metabolizable energy → Digestible energy → Net energy b) Gross energy → Digestible energy → Net energy → Metabolizable energy c) Gross energy → Digestible energy → Metabolizable energy → Net energy d) Digestible energy → Gross energy → Net energy → Metabolizable energy Answer: c)

What is the primary function of amino acids absorbed from the small intestine in animals? a) To be stored for later use as an energy reserve. b) To be directly utilized for ATP production in the mitochondria. c) To serve as building blocks for protein synthesis. d) To be efficiently converted into glucose via glycogenesis. Answer: c)

Which hormone primarily stimulates the synthesis of triglycerides (lipogenesis) in adipose tissues during the fed state? a) Glucagon b) Epinephrine c) Insulin d) Cortisol Answer: c)

The breakdown of triglycerides into glycerol and free fatty acids is stimulated by which hormone during the fasted state? a) Insulin b) Growth hormone c) Glucagon d) Thyroid hormone Answer: c)

Excessive mobilization of fatty acids from adipose tissues in dairy cows can lead to the liver producing ketone bodies, potentially resulting in which metabolic disorder? a) Diabetes mellitus b) Acidosis c) Ketosis d) Milk fever Answer: c)

Which characteristic distinguishes lipids from carbohydrates at a basic chemical level? a) Lipids contain nitrogen, while carbohydrates do not. b) Lipids are hydrophilic, while carbohydrates are hydrophobic. c) Lipids contain significantly more carbon and hydrogen bonds per unit weight. d) Carbohydrates are composed of fatty acids and glycerol. Answer: c)

Triglycerides are classified as which type of glycerol-based lipid? a) Compound lipid b) Phospholipid c) Simple lipid d) Glycolipid Answer: c)

In the omega nomenclature system for fatty acids, where does the carbon numbering begin? a) At the carboxyl end. b) At the glycerol backbone attachment point. c) At the methyl end. d) At the double bond closest to the carboxyl group. Answer: c)

Which of the following is an omega-3 fatty acid? a) Oleic acid (18:1 ω-9) b) Linoleic acid (18:2 ω-6) c) α-Linolenic acid (18:3 ω-3) d) Arachidonic acid (20:4 ω-6) Answer: c)

What is the primary function of mixed micelles in lipid digestion and absorption in monogastric animals? a) To emulsify large fat globules in the intestinal lumen. b) To hydrolyze triglycerides into fatty acids and glycerol. c) To transport fatty acids and monoglycerides across the unstirred water layer to the enterocytes. d) To package triglycerides into chylomicrons for lymphatic transport. Answer: c)

In ruminant animals, why does the consumption of diets rich in unsaturated fatty acids not necessarily lead to a high proportion of unsaturated fatty acids in their body fat? a) Because unsaturated fatty acids are preferentially used for ATP production. b) Because rumen microorganisms efficiently biohydrogenate unsaturated fatty acids into saturated fatty acids. c) Because the absorption of unsaturated fatty acids from the small intestine is limited. d) Because the mammary gland selectively incorporates saturated fatty acids into milk fat. Answer: b)

What is the initial step in the biohydrogenation of unsaturated fatty acids in the rumen? a) Hydrolysis of triglycerides. b) Oxidation of fatty acids. c) Isomerization of double bonds. d) Esterification with glycerol. Answer: c)

Which volatile fatty acid (VFA) is primarily utilized by the rumen epithelium for ATP production and is converted to beta-hydroxybutyrate (BHB) before entering the bloodstream? a) Acetate b) Propionate c) Butyrate d) Valerate Answer: c)

In ruminants, the majority (around 80%) of the glucose required by the animal is supplied by: a) Direct absorption of glucose from the small intestine. b) Breakdown of glycogen stores in the liver. c) Gluconeogenesis in the liver from propionate. d) Fermentation of carbohydrates in the large intestine. Answer: c)

Which enzyme is crucial for the transfer of acetyl-CoA from the mitochondria to the cytoplasm for de novo fatty acid synthesis in non-ruminant animals? a) Fatty acyl-CoA synthetase b) Citrate synthase c) ATP citrate lyase d) Hormone-sensitive lipase Answer: c)

In the process of triglyceride synthesis, glycerol must first be converted to: a) Free glycerol b) Fatty acyl-CoA c) Glycerol-3-phosphate d) Acetyl-CoA Answer: c)

Beta-oxidation is a metabolic process that occurs in the ________ and results in the breakdown of fatty acids into ________. a) Cytoplasm; glucose molecules b) Mitochondria; acetyl-CoA c) Endoplasmic reticulum; pyruvate molecules d) Nucleus; amino acid molecules Answer: b)

Which enzyme catalyzes the activation of free fatty acids by attaching coenzyme A, requiring the expenditure of ATP? a) Lipoprotein lipase b) Hormone-sensitive lipase c) Fatty acyl-CoA synthetase (thiokinase) d) Pancreatic lipase Answer: c)

In ruminants, why is acetate considered a primary precursor for fatty acid synthesis in adipose and mammary tissues? a) Because ruminants have a high rate of glucose absorption from the small intestine. b) Because the liver efficiently converts acetate to glucose for peripheral tissues. c) Because ruminants have limited activity of ATP citrate lyase, sparing glucose for other essential functions. d) Because acetate directly enters the mitochondria for fatty acid synthesis. Answer: c)

The conversion of starch to propionate in the rumen of a dairy cow is an example of: a) Gluconeogenesis b) Glycogenolysis c) Fermentation d) Lipogenesis Answer: c)

Which vitamin plays a crucial role in the conversion of propionate to phosphoenolpyruvate (PEP) during gluconeogenesis in ruminants? a) Vitamin A b) Vitamin D c) Vitamin B12 d) Vitamin E Answer: c)

Lactose, the primary sugar in milk, is synthesized in the mammary cells of cows from which two building blocks? a) Glucose and fructose b) Galactose and fructose c) Glucose and galactose d) Sucrose and lactose Answer: c)

Which of the following enzymes is responsible for digesting triglycerides within circulating lipoproteins, releasing fatty acids for uptake by tissues? a) Pancreatic lipase b) Lingual lipase c) Hormone-sensitive lipase d) Lipoprotein lipase (LPL) Answer: d)

The conversion of glucose to glucose-6-phosphate by hexokinase is important for which reason? a) It is the rate-limiting step of glycolysis. b) It facilitates the transport of glucose out of the cell. c) It prevents glucose from returning to the blood, trapping it within the cell. d) It directly produces a significant amount of ATP. Answer: c)

Glycogenolysis, the breakdown of glycogen to release glucose, is primarily stimulated by which hormone? a) Insulin b) Glucagon c) Cortisol d) Growth hormone Answer: b)

In protein metabolism, the removal of an amino group from an amino acid is known as: a) Transamination b) Deamination c) Peptide bond formation d) Protein hydrolysis Answer: b)

Carnivorous animals rely heavily on which metabolic process to maintain stable blood glucose levels due to their low carbohydrate intake? a) Glycogenesis b) Lipogenesis c) Gluconeogenesis d) Glycogenolysis Answer: c)

Treating feeds with formaldehyde can protect unsaturated fatty acids from biohydrogenation in the rumen by primarily inhibiting which process? a) Hydrogenation b) Isomerization c) Lipolysis d) Absorption Answer: c