Chapter 4: Exercise Metabolism and Bioenergetics Flashcards
bioenergetics
the study of energy in the human body (aka energy meetabolism)
metabolism
all of the chemical reactions that occur in the body to maintain itself. metabolism is the process in which nutrients are acquired, transported, used, and disposed of by the body.
exercise metabolism
the examination of bioenergetics as it relates to the unique physiologic changes and demands placed on the body during exercise
substrates
the material or substance on which an enzyme acts
carbohydrates
organic compounds of carbon, hydrogen, and oxygen, which include starches, cellulose, and sugars, and are an important source of energy. all carbohydrates are eventually broken down in the body to glucose, a simple sugar.
glucose
- a simple sugar manufactured by by the body from carbohydrates, fat, and to a lesser extent protein, which serves as the body’s main source of fuel
- it is absorbed and transported in the blood, where it is circulated until it enters cells (with the aid of insulin) and is either used or stored as energy
glycogen
- the storage form of carbohydrates
- a string of glucose molecules that can be rapidly broken down into glucose and sued for energy during periods of prolonged or intense exercise
- the complex carbohydrate molecule used to store carbohydrates in the liver and muscles cells
- when carbohydrate energy is needed, glycogen is converted into glucose for use by the muscle cells
fat
one of the three main classes of foods and a source of energy in the body. fats help the body use some vitamins and keep the skin healthy. they also serve as energy stores for the body. in food, there are two types of fats, saturated and unsaturated.
triglycerides
- the chemical or substrate form in which most fat exists in food as well as in the body
- derived from fats eaten in foods or made in the body from other energy sources such as carbohydrates
protein
amino acids linked by peptide bonds, which consist of carbon, hydrogen, nitrogen, oxygen, and usually sulfur, and that have several essential biological compounds
gluconeogenesis
the formation of glucose from noncarbohydrate sources, such as amino acids
adenosine triphosphate
energy storage and transfer unit within the cells of the body
adenosine diphosphate
a high-energy compound occurring in all cells from which adenosine triphosphate (ATP) is formed
B-oxidation
the breakdown of triglycerides into smaller subunits called free fatty acids (FFAs) to convert FFAs into acyl-CoA molecules, which then are available to enter the Krebs cycle and ultimately lead to the production of additional ATP
excess postexercise oxygen consumption (EPOC)
the state in which the body’s metabolism is elevated after exercise
how does our body get energy from food?
- it must be converted into smaller units called substrates, including carbohydrates, proteins, and fats
- the energy stored in these substrate molecules is then chemically released in cells and stored in the form of a high energy compound called adenosine triphosphate (ATP)
what is the ultimate source of energy?
- the sun
- through photosynthesis, energy from the sun produces chemical energy and other compounds that are used to convert carbon dioxide into organic chemicals such as glucose
main sources of chemical energy for most organisms
- carbohydrates, fats, and protein
- the energy from the oxidation of carbohydrates, fats, and proteins sustains the biochemical reactions required for life
true or false: dietary food directly provides energy to sustain life and support physical activity
- FALSE; indirectly
- it first has to be broken down by the digestive system into substrates
what can a lack of carbohydrates cause?
- fatigue
- poor mental function
- lack of endurance and stamina
what is the primary end product after the digestion of carbohydrates?
the formation of glucose
what happens to calories that are consumed but not immediately needed by cells of tissues?
they are converted to triglycerides and transported to fat cells where they are stored
benefits of fats as a fuel source
most people have an inexhaustible supply of fat, which can be broken down into triglycerides and used for energy during prolonged physical activity or exercise
true or false: protein supplies the majority of energy during exercise
- FALSE
- protein rarely supplies much energy during exercise and in many descriptions is ignored as a significant fuel for energy metabolism
when does protein become a significant source of fuel?
- starvation
- during a negative energy balance, amino acids are used to assist in energy production
- this is called gluconeogenesis
what is one of the primary sources of immediate energy for cellular metabolism?
-stored in the chemical bonds of adenosine triphosphate (ATP)
what happens when the chemical bonds that hold ATP together are broken?
-energy is released for cellular work (ex. muscle contraction), leaving behind another molecule called adenosine diphosphate (ADP)
what is one of the functions of energy metabolism?
to harness enough energy to reattach a phosphate group to an ADP and restore ATP levels back to normal to perform more work
how to muscle contraction occur?
energy is used to form the myosin-actin cross-bridges that facilitate muscle contraction
how many ATPs are needed for one cycle of a cross-bridge?
2
muscle contraction steps
- enzyme separates a phosphate from the ATP, releasing energy
- energy allows the cross-bridge to ratchet the thin actin filament toward the center of the sarcomere
- another ATP is needed to release the cross-bridge so that it can flip back up and grab the next actin active site and continue the contractile process
- when all the ATP is completely depleted, there is no energy to break the connection between cross-bridges and actin active sites, and the muscle goes into rigor
any form of exercise can be defined by which 2 factors?
- intensity
2. duration
intensity and duration relationship
inverse (negative)
how much of the energy released from ATP is actually used for cellular work (ex. muscle contraction)?
about 40%
what happens to the rest of the energy from ATP?
it is released as heat
what happens when the enzyme ATPase combines with an ATP molecule?
- it splits the last phosphate group away, releasing a large amount of free energy, approximately 7.3 kcal per unit of ATP
- once the phosphate group has been split off, what remains is ADP and an inorganic phosphate molecule (Pi)
ATP equation
ATP <> ADP + Pi + energy release
what must happen before ATP can release additional energy again?
it must add back another phosphate group to ADP through a process called phosphorylation
3 metabolic pathways in which cells can generate ATP
- the ATP-PC system
- the glycolytic system (glycolysis)
- the oxidative system (oxidative phosphorylation)
ATP-PC system
the process of creating a new ATP molecule from a phosphocreatine molecule
which system is the simplest and fastest?
ATP-PC system
is the ATP-PC aerobic or anaerobic?
anaerobic (occurs without the presence of oxygen)
what type of exercise does the ATP-PC system provide energy for?
- high-intensity, short duration
- ex) heavy loads with only a few repetitions, or short sprinting events
true or false: the ATP-PC is only activated during exercise that lasts less than 15 seconds
FALSE: this system is activated at the onset of activity, regardless of activity, because of its ability to produce energy very rapidly in comparison with the other systems
during an all-out sprint, how many seconds could the ATP and PC stores supply energy for before complete exhaustion?
10-15 seconds
phosphagens
ATP and PC together
is glycolysis anaerobic or aerobic?
anaerobic
anaerobic glycolysis
the chemical breakdown of glucose to produce ATP
what must happen before glucose or glycogen can generate energy?
it must be converted into a compound called glucose-6-phosphate
how many molecules of ATP are required to convert glucose to glucose-6-phosphate?
1 ATP molecule
what is the end result of glycolysis?
2 ATP for each unit of glucose and 3 ATP from each unit of glycogen
pyruvic acid
produced in aerobic glycolysis
lactic acid
produced in anaerobic glycolysis
what duration of exercise can glycolysis produce energy for?
30-50 seconds
about 8-12 repetitions
the oxidative system
- uses substrates with the aid of oxygen to generate ATP
- aerobic
3 oxidative / aerobic systems
- aerobic glycolysis
- the krebs cycle
- the electron transport chain (ETC)
in the presence of oxygen, what is pyruvic acid converted into?
acetyl coenzyme A (acetyl CoA)
end product of aerobic glycolysis (acid)
pyruvic acid
end product of anaerobic glycolysis (acid)
lactic acid
acetyl CoA function
contributes substrates for use in the second process of oxidative production of ATP, called the Krebs cycle
what does the complete oxidation of acetyl CoA produce?
- 2 units of ATP
- carbon dioxide
- hydrogen
what is the function of the hydrogen ions released during glycolysis and the Krebs cycle?
- they combine with other enzymes
- in the third process of oxidation, they provide energy for the oxidative phosphorylation of ADP to form ATP (electron transport chain)
how many ATP does the complete metabolism of a single glucose molecule produce?
35-40 ATP
first step in the oxidation of fat
B-oxidation (beta oxidation)
how does the process of B-oxidation begin?
with the breakdown of triglycerides into smaller subunits called free fatty acids (FFAs)
what is the purpose of B-oxidation?
to convert FFAs into acyl-coA molecules, which then are available to enter the Krebs cycle and ultimately lead to the production of additional ATP
what is the preferred fuel substrate for the oxidative production of ATP?
carbohydrates
true or false: fats require more oxygen to produce ATP than carbohydrates
true
true or false: carbohydrate oxygen produces far more ATP per molecule of carbohydrate
FALSE: fat oxidation produces far more ATP per molecule compared with a molecule of carbohydrate
end results of aerobic metabolism of carbohydrates and fats
water and carbon dioxide
which is faster: the aerobic breakdown of glucose and fat, or the anaerobic metabolism of glucose
the anaerobic metabolism of glucose
which is faster: the anaerobic metabolism of glucose or the ATP-PC cycle
ATP-PC cycle
why is aerobic metabolism capable of producing energy for an indefinite period of time?
because everyone has an ample supply of storage fat
what are the most important factors for regulating energy utilization during exercise?
intensity and duration
immediate energy systems
ATP-PC
short-term energy systems
glycolysis
long-term energy systems
aerobic
after how many minutes of exercise are the majority of muscle glycogen stores depleted?
90 minutes
true of false: through a combination of training and high carbohydrate intake, it is possible to store significantly greater quantities of glycogen, perhaps up to 50% more, allowing athletes to exercise for longer periods before fatiguing or reaching a point of exhaustion
TRUE
what type of exercise are measurements made for the purpose of assessing exercise metabolism typically made during?
steady-state exercise
steady-state exercise
exercise performed at a constant pace (intensity)
indirect measurements for the bioenergetics of exercise
use various modes of exercise (e.g. treadmill, ergometer) while measuring the concentrations of oxygen and carbon dioxide and volume of expired air
physiologic functions to measure the bioenergetics of exercise
- heart rate
- blood pressure
- exercise load or work output
supine
lying down
true or false: the body prefers aerobic or oxidative metabolism
TRUE: because carbon dioxide and water are more easily eliminated
what does the body rely on at the start of exercise?
- the ATP-PC cycle (Resulting in a reduction of ATP and PC levels and an increase in ADP and creatine), since aerobic metabolic pathways are too slow to meet initial demands
- also from anaerobic metabolism of floccose early into the exercise period
amount of unmet energy demand
the difference between the oxygen consumption curve and total energy needs
what is leftover ATP used for?
- ATP above and beyond what is needed for recovery is produced to help reestablish baseline levels of ATP and PC
- also assists with clearing metabolic end products
how long does recovery of the ATP-PC cycle take?
approximately 90 seconds
true or false: if the period of high0intensity work is longer, the recovery period will take longer
true
recovery
- an aerobic event to set ATP-PC concentrations back toward normal
- the aerobic elimination of lactic acid
respiratory quotient (RQ)
the amount of carbon dioxide (CO2) expired divided by the amount of oxygen (O2) consumed
when is the RQ measured?
rest or at steady state of exercise
what is the RQ measured with?
a metabolic analyzer
what is needed to determine the relative contribution of fats and carbohydrates as fuel sources?
- RQ
- VO2
- VCO2
RQ of 1.0
carbohydrates are supplying 100% of the fuel for metabolism
RQ of 0.7
fats are supplying 100% of the fuel for metabolism
fat-burning zone myth
the inaccurate idea that people burn more fat at lower-intensity exercise because such east work does not require getting energy quickly from carbohydrates
