Multiple Choice Questions (MCQs)
- What is the primary energy source for cardiac metabolism under normal conditions?
a) Glucose
b) Lactate
c) Free Fatty Acids (FFA)
d) Amino Acids
Answer: c) Free Fatty Acids (FFA) - What percentage of myocardial cell volume is composed of mitochondria?
a) 20%
b) 35%
c) 50%
d) 60%
Answer: b) 35% - Which process is primarily responsible for converting ADP back into ATP during myocardial metabolism?
a) Beta-oxidation
b) Glycolysis
c) Oxidative Phosphorylation
d) Creatine Phosphate Hydrolysis
Answer: c) Oxidative Phosphorylation - What secondary fuel source is utilized by the myocardium during intense exercise?
a) Amino Acids
b) Lactate
c) Ketones
d) Pyruvates
Answer: b) Lactate - What metabolic pathway is primarily involved in oxidizing free fatty acids for ATP production?
a) Glycolysis
b) Beta-oxidation
c) Citric Acid Cycle
d) Oxidative Phosphorylation
Answer: b) Beta-oxidation - What is the function of creatine phosphate in cardiac metabolism?
a) Store oxygen for aerobic respiration
b) Facilitate rapid ATP regeneration
c) Provide lactate during exercise
d) Activate oxidative phosphorylation
Answer: b) Facilitate rapid ATP regeneration - Which of the following is a key feature of cardiac metabolism?
a) Reliance on anaerobic respiration
b) High resistance to fatigue
c) Predominantly using amino acids as fuel
d) Minimal mitochondrial density
Answer: b) High resistance to fatigue - What role do mitochondria play in myocardial cells?
a) Store glucose for energy
b) Facilitate anaerobic glycolysis
c) Support continuous ATP production through oxidative metabolism
d) Transport oxygen to myocardial fibers
Answer: c) Support continuous ATP production through oxidative metabolism - Which fuel sources are considered minor contributors to cardiac metabolism?
a) Free Fatty Acids and Glucose
b) Ketones, Amino Acids, and Pyruvates
c) Lactate and Glucose
d) Oxygen and Creatine Phosphate
Answer: b) Ketones, Amino Acids, and Pyruvates - Why is the myocardium highly resistant to fatigue?
a) It relies on anaerobic glycolysis.
b) It has a high mitochondrial density and efficient oxidative metabolism.
c) It stores large amounts of creatine phosphate.
d) It only uses glucose as its energy source.
Answer: b) It has a high mitochondrial density and efficient oxidative metabolism.
Fill in the Blanks
- The primary energy source for cardiac metabolism is ________.
Answer: Free Fatty Acids (FFA) - Approximately ________% of myocardial cell volume consists of mitochondria.
Answer: 35 - ________ is utilized by the heart during intense exercise or increased metabolic demand.
Answer: Lactate - Creatine phosphate facilitates rapid ________ regeneration during sudden energy demands.
Answer: ATP - The myocardium depends on ________ respiration for efficient energy production.
Answer: aerobic
True or False
- The heart primarily uses anaerobic metabolism to meet its energy demands.
Answer: False - Lactate serves as a secondary fuel source for the myocardium during exercise.
Answer: True - The high mitochondrial density in myocardial cells contributes to their resistance to fatigue.
Answer: True - Creatine phosphate acts as a long-term energy storage molecule for the heart.
Answer: False - Metabolic flexibility allows the heart to adapt to different fuel sources based on physiological needs.
Answer: True
Subjective Questions
- Discuss the importance of mitochondria in myocardial cells for cardiac function.
Answer: Mitochondria occupy approximately 35% of the volume in myocardial cells, making them crucial for cardiac function. They house enzymes for the citric acid cycle and oxidative phosphorylation, ensuring continuous ATP production to meet the heart’s high energy demands. This prevents myocardial fatigue and supports sustained contraction and relaxation. The high mitochondrial density is essential for the myocardium’s reliance on aerobic metabolism and resistance to fatigue. - Explain how metabolic flexibility benefits the myocardium during different physiological conditions.
Answer: Metabolic flexibility allows the myocardium to adapt to varying fuel availability and metabolic demands. Under normal conditions, free fatty acids are the primary energy source. During intense exercise or stress, the heart shifts to using lactate and glucose as secondary fuels. Minor contributors such as amino acids, ketones, and pyruvates provide additional energy under pathological conditions. This adaptability ensures that the heart can sustain its function under diverse physiological states, maintaining efficient energy production and contraction.