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WorksheetsExercise and Bioenergetics Quiz
Total questions: 25
Worksheet time: 13mins
During high-intensity exercise, what is the primary immediate buffer of ATP concentration in skeletal muscle?
Mitochondrial oxidative phosphorylation
Phosphocreatine via the creatine kinase reaction
Anaerobic glycolysis via lactate dehydrogenase
Hepatic gluconeogenesis
Which step of glycolysis is considered the major rate-limiting (committed) step in skeletal muscle during exercise?
Glucose-6-phosphate to fructose-6-phosphate
Fructose-6-phosphate to fructose-1,6-bisphosphate (PFK-1)
1,3-bisphosphoglycerate to 3-phosphoglycerate
Phosphoenolpyruvate to pyruvate
In the creatine kinase reaction (PCr + ADP + H+ ↔ Cr + ATP), an accumulation of H+ during intense exercise tends to shift the equilibrium in which direction?
Toward ATP production
Toward PCr resynthesis
No effect; H+ is not involved
Toward Cr + ADP
Using contemporary P/O ratios (NADH ≈ 2.5 ATP, FADH2 ≈ 1.5 ATP), the net ATP yield from complete oxidation of palmitate (C16:0) is closest to:
84 ATP
96 ATP
106 ATP
129 ATP
Which pair of reactions in glycolysis produces ATP directly via substrate-level phosphorylation?
Hexokinase and phosphoglucose isomerase
PFK-1 and aldolase
Phosphoglycerate kinase and pyruvate kinase
Glyceraldehyde-3-phosphate dehydrogenase and enolase
What is the single best explanation for why RER can exceed 1.0 during severe exercise?
Fat oxidation produces more CO2 than O2 consumed
Increased protein oxidation elevates CO2
Bicarbonate buffering of H+ generates additional CO2 independent of mitochondrial oxidation
O2 uptake is capped, forcing anaerobic CO2 release from lactate
The lactate produced in fast-twitch fibers is best described as:
A metabolic dead-end that must be excreted
A substrate that can be oxidized in other tissues and fibers
A toxin that directly inhibits actin-myosin binding
The primary cause of delayed-onset muscle soreness
A decrease in mitochondrial coupling efficiency during exercise most directly implies:
Less O2 consumption for the same ATP production
More ATP produced per NADH oxidized
More O2 consumption for the same ATP production due to proton leak
Complete inhibition of the TCA cycle
Which regulatory change most directly increases carbohydrate oxidation at a given workload during acute exercise?
Inhibition of pyruvate dehydrogenase (PDH)
Activation (dephosphorylation) of PDH
Inhibition of glycogen phosphorylase
Inhibition of PFK-1 by AMP
When oxygen delivery is suddenly reduced at a fixed workload, which variable typically changes first to maintain ATP resynthesis?
Mitochondrial density
Rate of ATP utilization
Contribution from anaerobic glycolysis
Hemoglobin concentration
During moderate exercise, skeletal muscle GLUT4 translocation is increased mainly via:
Insulin signaling only (PI3K-Akt)
Contraction-mediated pathways involving AMPK and Ca2+ signaling
Cortisol receptor activation
Thyroid hormone receptor activation
Which hormone is most directly responsible for counterregulation of falling blood glucose during prolonged exercise (especially in individuals with type 1 diabetes)?
Leptin
Glucagon
Calcitonin
Aldosterone
IL-6 released from contracting skeletal muscle is best characterized as:
An adipokine that suppresses lipolysis
A myokine that can increase hepatic glucose output and lipolysis
A neurotransmitter that reduces ventilation
A steroid hormone from the adrenal cortex
The baroreflex 'resetting' observed during exercise is most consistent with:
Complete inactivation of baroreceptors
A shift of the operating point to defend a higher arterial pressure
Loss of sympathetic control of HR
Permanent reduction in vascular resistance post-exercise
Cortisol’s acute metabolic role during prolonged exercise is best described as:
Promoting glycogen synthesis in muscle
Supporting gluconeogenesis and mobilization of amino acids and fats
Blocking hepatic glucose output
Directly increasing muscle protein synthesis
Which second messenger is most directly increased by beta-adrenergic receptor activation in muscle and liver?
cAMP
IP3
cGMP
NADPH
According to the Fick principle, whole-body VO2 equals:
HR × SV
Q × (CaO2 − CvO2)
MAP ÷ TPR
SV ÷ HR
At maximal exercise, the largest contributor to increased cardiac output in untrained individuals is typically:
Increased stroke volume only
Increased heart rate only
Equal increases in HR and SV across all intensities
Reduced preload
The primary mechanism for increased venous return during rhythmic dynamic exercise is:
Reduced skeletal muscle pump
Increased blood viscosity
Skeletal muscle pump and respiratory pump
Decreased sympathetic venoconstriction
Functional sympatholysis refers to:
Sympathetic activation causing vasodilation in skin
Local metabolic vasodilation blunting sympathetic vasoconstriction in active muscle
Parasympathetic dominance at high intensities
Complete loss of vasomotor tone after exercise
Which local factor is most directly associated with exercise-induced vasodilation in active skeletal muscle?
Endothelin-1
Adenosine and increased K+ / H+ / CO2
Increased angiotensin II
Decreased nitric oxide
During steady-state submaximal exercise, mean arterial pressure (MAP) typically:
Decreases substantially due to vasodilation
Remains unchanged because Q and TPR do not change
Increases modestly because Q rises more than the fall in TPR
Falls to the level of diastolic pressure
The increase in a-vO2 difference during incremental exercise is primarily due to:
Lower arterial O2 content
Greater O2 extraction by working muscles (lower venous O2 content)
Reduced hemoglobin concentration
Reduced capillary density
A key reason stroke volume can plateau at higher intensities is:
Increased preload time due to longer diastole
Reduced venous return from muscle pump
Reduced ventricular filling time from high HR (shortened diastole)
Elimination of sympathetic inotropy
With upright dynamic exercise, cutaneous blood flow generally:
Falls continuously as intensity increases
Increases early, then may plateau or fall at very high intensities
Is unchanged because skin is not active tissue
Always exceeds muscle blood flow
