Lesson 14: Fuel Use Quiz

Lactate If exercise intensity is very high and adequate amounts of oxygen are not available, pyruvate can be converted into lactate, which may be transported out of the active cell and used for energy by other cells in the body. This allows for the continued production of pyruvate via anaerobic glycolysis, resulting in a steady supply of ATP.

During high-intensity workouts, when there is inadequate oxygen, pyruvate converts into _______________.

Plasma free fatty acids During low-intensity exercise, plasma free fatty acids are the primary source of fat energy. Furthermore, as the duration of the exercise increases, there is a progressive rise in the role of plasma free fatty acids as a fuel source.

During low-intensity exercise, _______________ is/are the primary source of fat energy.

Mitochondria; cytoplasm Aerobic glycolysis is a metabolic pathway that occurs within highly specialized cell structures called the mitochondria, which are often called the powerhouses of the cell. Anaerobic glycolysis occurs within the cytoplasm of the cell and involves the incomplete breakdown of glucose to a simpler substance called pyruvate.

Aerobic glycolysis occurs in the cells' _______________, and anaerobic glycolysis occurs in the cells' _______________.

The breakdown of fatty acids to produce ATP Beta oxidation, also called fatty acid oxidation, occurs within the mitochondria and is an aerobic pathway that breaks down fatty acids to produce ATP.

Beta oxidation is a result of _______________.

Low-intensity; high-intensity Blood glucose plays a greater role in energy metabolism during low-intensity exercise, as the body's ability to deliver glucose is comparable to the rate of glucose utilization. However, muscle glycogen is the primary source of carbohydrate during high-intensity exercise, as the rate of glucose utilization far exceeds the rate of glucose delivery.

Blood glucose is efficient in fueling _______________ exercise, whereas muscle glycogen is more efficient in fueling _______________ exercise.

Muscle glycogen During the first hour of submaximal endurance exercise, such as a half-marathon, much of the carbohydrate metabolized by muscle comes from muscle glycogen.

During the first hour of a half-marathon, carbohydrate metabolism is fueled by _______________.

FALSE During high-intensity exercise, the total number of calories burned is much higher than during low-intensity exercise, and negates the higher percentage coming from fat. During low-intensity bouts, a higher percentage of calories is coming from fat, but the total number of fat calories is less than during high-intensity workouts. It is important to remember that the total number of calories burned is what determines weight loss, regardless of the source of those calories.

Low-intensity exercise is the best way to lose weight because it burns a higher percentage of fat than exercise at a higher intensity

Oxygen Oxidative glycolysis, which occurs within the mitochondria, is limited mainly by the capacity of the cardiorespiratory system to deliver oxygen to the active cells.

Oxidative glycolysis occurs as a result of sufficient _______________ in the mitochondria.

Phosphogen system The phasphagen system is instantaneously available for muscular contraction and is essential during short-term, high-intensity activities such as sprinting or strength-training exercises like a plyometric jump squat.

The primary energy system used during a plyometric jump squat is the ______________

Protein Of the three macronutrients, relatively little protein is used for energy production except in extreme cases of caloric restriction. Protein is principally used in the growth and repair of tissue or is excreted.

Very little of the __________ a person consumes is used for energy production.

Carbohydrate Carbohydrate serves as the major food fuel for the metabolic production of adenosine triphosphate (ATP), which is a chemical compound required for all cellular work. Importantly, carbohydrate is the only macronutrient whose stored energy generates ATP anaerobically. This is crucial during maximal exercise that requires rapid energy release above levels supplied by aerobic metabolism.

What is the only macronutrient whose stored energy generates adenosine triphosphate (ATP) anaerobically?

Glucose During exercise, some of the lactate that is produced by skeletal muscles is transported to the liver via the blood. The liver then converts the lactate back to glucose and releases it into the bloodstream to be transported back to the skeletal muscles to be used as an energy source. The cycle of lactate-to-glucose between the muscle and the liver is called the Cori cycle. This process works to preserve the body's glucose levels and to ensure that the muscles have adequate fuel to perform work.

When lactic acid accumulates in the body during exercise, the liver converts it to _______________ as a way to continue fueling the muscle.

Phosphagen system The total amount of ATP and creatine phosphate (CP) stored in muscle is very small, and thus the amount of energy available for muscular contraction is extremely limited. There is probably enough energy available from the phosphagens for only about 10 seconds of all-out exertion, if there were not continual resynthesis of ATP.

Which of the primary energy systems supplies enough energy for no more than 10 seconds of all-out exertion?

Carbohydrate Compared to fatty-acid metabolism, glucose metabolism requires less oxygen, so the body will use more glucose and less fat for energy production as exercise intensity increases. The respiratory exchange ratio is a marker of the proportion of fat or carbohydrate that is being used for fuel at different exercise intensities. At higher intensities, carbohydrate becomes the primary source of fuel.

_______________ is the primary nutrient utilized during high-intensity exercise.