Knowledge Check Quizzes (Weeks 1-4)

During muscle contraction, myosin binds to troponin when Ca⁺⁺ is bound to actin.

False

During muscle contraction, Ca⁺⁺ binds to troponin, causing a confirmational change that moves tropomyosin away from the binding sites on actin.

True

Myosin heads have ATPase activity, resulting in the hydrolysis of ATP to ADP and Pi.

True

Release of Pi from the myosin head initiates the power stroke (i.e., the myosin head pulling on actin filaments to induce contraction).

True

NAD is the oxidized form of NADH.

True

NADH is the reduced form of NAD

True

An increase in myocellular ADP concentrations causes increased ATP resynthesis as a function of equilibrium reactions.

True

Both creatine kinase and adenylyl kinase enzymes will synthesize more ATP in response to an increase in ADP concentrations.

True

Our cells are remarkably adapted to defend against significant deviations in ATP and is the purpose of our bioenergetic pathways

True

Exercise is characterized by a rapid and prolonged decrease in cellular ATP concentration.

False

Glycolysis is the process of breaking down 6-carbon glucose into two 3-carbon pyruvate molecules.

True

Glycolysis occurs in the mitochondrial matrix

False; occurs in the cytosol of cells

Beta oxidation occurs in the cytosol.

False; occurs in the mitochondria.

When oxygen is limiting and free NAD is needed for continued glycolysis, pyruvate can be reduced to lactate.

True

Acetyl-CoA (2-carbons) is combined with oxaloacetate (4-carbons) to form 6-carbon citrate as the first step of the TCA cycle.

True

Fats, carbohydrates and proteins can all form acetyl-CoA, thereby contributing carbons to the TCA cycle.

True

Within the electron transport system, NADH donates electrons at complex IV.

False, NADH donates electrons at complex I.

Mitochondrial complexes I, III and IV use the energy from electron transfer to pump H+ against their electrochemical gradient, into the space between the inner and outer mitochondrial membranes.

True

Oxygen is reduced to H₂O at complex IV, serving as the final electron acceptor of the electron transfer system.

True

Oxygen consumption measured via indirect calorimetry reflects oxygen consumption at mitochondrial complex IV

True

VO₂max reflects with our maximal ability to engage in oxidative phosphorylation

True

Elevated post-exercise oxygen consumption (EPOC) is proportional to exercise intensity and is equal to O₂ deficit at the onset of exercise.

False, EPOC generally exceeds O₂ deficit due to the “slow components” that require continued ATP production and oxygen consumption as we cool down post exercise.

long duration exercise is predominately limited by how much fat we have stored.

False: We have enough stored fat energy to exercise for days on end! By contrast, stored carbohydrate is limiting.

Amino acids are the principal source of acetyl-CoA during exercise.

False; Protein contributes 3-5% of energy under most circumstances. We generally preserve amino acids for the building blocks of proteins

Fatty acids are the principal source of fuel during low-intensity exercise (e.g. 25% VO₂max).

True

VO₂ provides an indirect but highly accurate measurement of energy expenditure.

True

RER of 0.93 indicates oxidative phosphorylation is largely being fueled by carbohydrate oxidation

True

During exercise catecholamines can activate protein kinase A (PKA) which phosphorylates and thereby regulates enzymes important for control of glycogenolysis and lipolysis

true

Muscle cells engage in gluconeogenesis during exercise to maintain blood glucose concentration

false

Blood insulin levels are rapidly lowered after the onset of exercise

true

The liver can use lactate as gluconeogenic substrate

true

lipolysis is the process of breaking down glycogen into glucose

false

mechanical and chemical signals arising from muscle contraction facilitate nutrient transport

true

Glucose-6-phosphatase removes a phosphate from otherwise “trapped” glucose within the liver

true

Endurance athletes typically have a high proportion of type I muscle fibers.

true

Type IIa muscle fibers have the highest/fastest ATPase activity.

false

All muscle fibers of a given motor unit will be the same fiber type and they are receiving the exact same contractile stimulus.

true

Motor units are recruited according to the size principal, with smaller motor units recruited first

true

Type IIx muscle fibers are typically recruited prior to type I muscle fibers for any given task.

false

The muscle spindle reflex results in increased skeletal muscle contractile force generation.

true

The golgi tendon organ reflex results in skeletal muscle relaxation.

true