Lesson 14: Bioenergetics of Exercises + Fuel Use During Physical Activity Flashcards
ATP is stored within muscles but where does the majority of ATP used for muscle contraction come from?
the food we eat
What is ATP?
The immediate chemical energy needed for all cellular function
What does ATP stand for?
Adenosine Triphosphate
What is ATP the combination of?
Adenosine and 3 phosphate groups
Carbs/proteins/fats are digested down to their simplest forms and absorbed into the blood before transporting to metabolically active cells, from here, what/where do they go?
They either immediately enter the metabolic pathway for ATP Production or are stored for later use.
The protein we eat is usually used for growth and repair of cellular structures or excreted as waste, but can amino acids be converted to and used in?
Glucose in the liver through gluconeogenesis and used in the nerves/muscles.
In a state of starvation, what happens to protein?
It is catabolized and converted to glucose in the liver.
Why is energy released from ATP?
ATP is adenosine and 3 phosphate groups, there is special high-energy bonds between the phosphate groups that when broken, releases energy to the cell that can directly use it to perform cellular function.
If there is no ATP present in a muscle looking to contract, what will happen?
It won’t be able to contract until there is a source of ATP
Why is our human physiology organized to provide uninterrupted sources of ATP?
Due to our ancestors need to exercise in order to procure food, pursure mates and escape predators.
Why must ATP be continuosly resynthesized in one of the three energy systems?
Because although it can be stored in a cell, the amount of ATP that is stored and immediately available (for muscular contraction) is very limited and will only provide seconds of energy.
What two compounds are referred to as phosphagens when combined?
ATP and Creatine Phosphate
What is another high-energy phosphate compound found within muscle cells? (Not ATP)
Creatine Phosphate
When ATP is broken down for muscular contraction, what is it re-synthesized from?
the breakdown of creatine phosphate
The energy released from breaking the Creatine Phosphate’s bone is used to reconstitute ATP from what? (2)
Adenosine Diphosphate (ADP) and P.
Why can Creatine Phosphate levels drop very low in comparison to ATP Levels?
Due to CP constantly reconstructing ATP.
During heavy exercise, what combines to make ATP and AMP?
x2 ADP (adenosine diphosphate)
why is it important that ADP combines to make ATP and AMP?
it results as another pathway for rapid re-synthesization of ATP and because AMP is an important signalling molecule that tells your body to adapt to training in a way that increases production of ATP.
How many seconds of energy will the total of ATP and CP stored in a muscle provide during all-out exertion exercise when ATP is no continuosly resynthesized?
10 seconds
What is anaerobic glycolysis?
the anaerobic production of ATP from carbohydrates
How does anaerobic glycolysis make ATP?
it uses the energy contained in glucose
Anaerboic Glyoclysis provides a convenient intermediate/halfway energy system between the __________ system and ________ ________ of ATP.
phosphagen
aerobic production
When is anaerobic glycolysis required?
when energy is needed to perform activities that require large bursts of energy over a longer period of time than the phosphagen system will allow (around 1-3 mins)
Anaerobic glycolysis occurs within the _______1 of the ____2 and involves the incomplete breakdown of _______3 or _________4 to a simpler substance, _________5 to be used in the mitochondria by the aerobic energy system.
1 cytoplasm 2 cell 3 glucose 4 glycogen 5 pyruvate
What is pyruvate?
pyruvate is a key intermediate compound in several metabolic pathways throughout the cell
If energy is very high and there are little amounts of oxygen available, what can pyruvate be converted into and transported to do?
Pyruvate will be converted into lactate and will transport out of the active cell to be used for energy by other cells in the body.
What does continuous production of pyruvate via anaerobic glycolysis result in?
a steady stream of ATP
What is lactate accumulation attributed to changes in?
muscle pH (acidity)
What does changes in muscle pH contribute to?
muscle fatigue
If the circulatory system and other inactive structures cannot maintain a good ratio of lactate in the muscle, what will occur?
Muscle fatigue will occur and therefore painful symptoms like ‘the burn’
Is it aerobic or anaerobic glycolysis that provides the main source of ATP during high-intensity exercise?
anaerobic
Can anaerobic glycolysis be used continusly or only for a specified amount of time during sustained activity?
sustained amount of time
What is the aerobic production of ATP used for?
activities that require a sustained amount of energy production
Aerobic metabolic pathways need a continous supply of oxygen delivered by the circulatory system, without oxygen, they cannot produce ATP - why?
because the metabolic fuels (carbs and fats) are burned in the presence of oxygen and the energy produced from burning these is what provides ATP.
What is the efficiency of cellular respiration? And what is most of it wasted as?
25%, most of it is wasted as heat.
Where does Aerobic Glycolysis/Oxidative Glycolysis occur and why?
in the mitochondria because they contain oxidative enzymes that are needed by the cell to utilize oxygen.
What is Aerobic/Oxidative Glycolysis limited by?
the capacity of the cardiorespiratory system to deliver oxygen to the active cells.
When sufficient oxygen is available, what is pyruvate converted into?
acetyl-CoA
In Aerobic/Oxidative Glycolysis, once pyruvate is converted to acetyl-CoA, what happens next?
the acetyl-CoA enters the Kreb’s cycle and electron-transport system to then produce ATP, CO2 and H2O.
What are fatty acid oxidation and beta oxidation?
they are metabolic pathways that occur within the mitochondria and require a continuous supply of oxygen to produce ATP.
Why is fat such an excellent source of stored energy?
because the aerobic metabolism of fat produces a large amount of ATP.
at rest, what does the body use for energy production?
glucose and fatty acids (via aerobic pathways)
During exercise and as intensity increases, does the body utilize glucose or fat more and why?
It utilizes glucose more for energy production as glucose metabolism requires less oxygen than fatty-acid metabolism.
What is the Respiratory Exchange Ratio (RER)?
a marker of the proportion of fat or carbohydrates that is being used for fuel at different exercise intensities.
How is Respiratory Exchange Ratio measured?
By evaluating both concentrations of CO2 produced and O2 consumed in expired air during steady state exercises.
What is the Respiratory Exchange Ratio formula?
RER = Co2 divided by O2 consumed
When the Respiratory Exchange Ratio value is at 1, the source of fuel is 100% ?
carbohydrates
when the Respiratory Exchange Ratio value is 0.7, the source of fuel is primarily 100 ?
fat
At rest, the Respiratory Exchange Ratio averages at 0.75, what percent of fat and carbohydrates are used here for fuel?
85% fat
15% carbs
As exercise intensity increases so does the Respiratory Exchange Ratio, what shift is reflected in this increase?
A shift from primarily fat metabolism to primarily carbohydrate metabolism
When is protein broken down for energy ue?
In extreme, sustained exercise events such as ultramarathons or in a clinical condition such as diabetes.
Why is assessing an individuals oxygen consumption a great measure of their ability to perform sustained endurance exercises?
Because the primary mechanism for creating energy is from the OXIDATION of glucose and fatty acids.
The more O2 taken in, transported and utilized = the more physical work can be done.
How can O2 consumption be determined?
by measuring the volume of air that an individual is breathing and the concentrations of O2 and Co2 exhaled.
What is Vo2 Max?
The amount of oxygen consumed at max levels of exertion.
How is Vo2 Max/Maximal Aerobic Capacity calculated?
Millilitres of oxygen consumed per KG of body weight per minute.
Why is the Vo2 Max measurement a relative measurement?
because the O2 consumption is divided by body weight
How can O2 consumption also be represented in absolute terms?
Liters of O2 consumed per minute - opposed to ml.
What is o2 consumption used to calculate?
the amount of calories that are expended during an activity.
How many kcals are approximately burned for every litre of O2 consumed?
5kcals
What is the metabolic pathway of triglycerides?
They are hydrolyzed to glycerol and free-fatty-acids and the long-chain fatty acids must be reduced to 2-carbon structures via beta-oxidation. They’re then converted to acetyl-CoA before entering in to the Kreb’s cycle.
Why must long-chain fatty acids be reduced to 2 carbon structures before converting to Acetyl-CoA?
because Acetyl-CoA is a small carbon structure.
Can Pyruvate reverse its formation into Acetyl-CoA?
No, this is an irreversible reaction.
What can excess carbs that aren’t used for energy be converted to and what process can they enter?
They can be converted to glycerol and enter the beta-oxidation process in reverse.
Excess carbs can enter the beta-oxidation process in reverse and manufacture 2 components needed to make ?
triglycerides
What is an important precursor for the manufacture of an intermediate product of the Kreb’s cycle that facilitates fat metabolism?
pyruvate
Reduction in pyruvate as seen in carb-restricted diets will impeded what?
the body’s ability to properly metabolize fats
Accumulation of partially metabolized fats will result in the manufacturing of ________ _______ as as way for the body to rid of the accumulated acetyl-CoA.
ketone bodies
What are ketone bodies?
water-soluble molecules that contain the ketone group produced by the liver from fatty acids
Proteins must undergo _______ to remove the amino group before metabolizing in the body?
deamination
What is deamination?
the removal of an amino group from a molecule
Amino Acids are either glucogenic or ketogenic, what are these based on?
The AA’s point of entry into the pathways.
Glucogenic Amino Acid’s can be converted to _______1 and generate _______2 via _____________.3
1 pyruvate
2 glucose
3 gluconeogenesis
Ketogenic Amino Acid’s are converted to _________1 and enter the ______ ______2 for energy.
1 acetyl-CoA
2 Kreb’s cycle
Out of carbohydrates, fats and proteins - which are primary sources for energy and which is not? Why?
Carbohydrates and fats are primary sources of energy whereas protein is used for repair and growth of muscles and only used for energy in severe cases such as starvation mode.
What is the pathway of fats?
It is broken down into fatty acids and either stored as adipose tissue or used to produce energy.
What is the pathway of carbohydrates?
They are broken into glucose and either immediately used for energy in the form of ATP or stored as glycogen in the muscles and liver. If there is an excess amount it is stored as adipose tissue.
What is the pathway of protein?
It is broken down into amino acids and primarily used to aid growth and repair of tissues. Any protein not used is then exreted as waste.
What is anaerobic glycolysis the breakdown of? And what is not present?
The breakdown of glucose ithout oxygen.
What does anaerobic glycolysis serve as an intermediate energy system between?
the phosphagen system and aerobic production of ATP
Anaerobic glycolysis breaks down pyruvate, what is this then used for?
It can either be used by the aerobic energy system or converted to lactate.
When does pyruvate convert to lactate?
When exercise intensity is very high and oxygen ability is limited.
Where is lactate transported when exercise intensity is high?
Out of the active cell to be used for energy in other cells.
What does pyruvate do when lactate is removed from the cell during anaerbic glycolysis?
It continues to create ATP production and creates a steady supply.
What is aerobic glycolysis limited by?
the amount of oxygen that is delivered to the active cells by the cardiorespiratory system.
When oxygen is present, what does glucose break pyruvate into?
acetyl-CoA
The anaerobic breakdown of fat can also produce ATP/energy, what is this process called?
fatty-acid oxidation or beta-oxidation
Ture or false, the body stores all 3 macros in various locations and releases them as energy depending on the type of activity performed?
True
What macronutrient is the only one whose stored energy generates ATP anaerobically?
Carbs
Anaerobic glycolysis of carbohydrates is crucial during what type of exercise?
maximal exercise that requires rapid energy release above levels supplied by aerobic metabolism
Where are blood glucose levels regulated primarily through?
through the glycogen that’s stored within the liver
What happens when the blood glucose levels are low?
glycogen from the liver is broken into glucose through glycogenolysis and is released into the bloodstream to be carried to the contracting muscle for fuel use.
Where does carbohydrate use come from during exercise?
the glycogen (that is) stored in the muscle tissue as well as from blood glucose
True or false, the intensity and duration of exercise is what determines the relative contribution of muscle glycogen and blood glucose?
True
During low-intensity exercise, is blood glucose or muscle glycogen higher for energy metabolism and why?
Blood glucose is higher as the body’s ability to deliver glucose is comparable to the rate of glucose utilization.
During high-intensity exercise, is blood glucose or muscle glycogen the primary source of fuel and why?
Muscle glycogen is the primary source as the rate of glucose utilization exceeds the rate of glucose delivery.
Why is there a higher rate of glucose utilization during high-intensity exercise?
Because there is an increased rate of glycogenolysis in the muscle
Why is there an increased rate of glycogenolysis during high-intensity exercise?
This is due to the recruitment of fast-twitch muscle fibers and elevated epinephrine levels.
True or false, epinephrine stimulates the production and release of both liver and skeletal muscle glycogen?
True
At what point does a higher rate of glucose utilization occur at? (Vo2 Max)
at 60% of a persons VO2 max or above.
Where does the carbs that are metabolized by muscle during the first hour of submaximal endurance exercise come from?
muscle glycogen
As exercise duration exceeds an hour, what happens to muscle glycogen levels and blood glucose?
muscle glycogen levels begin to decline and blood glucose (from glycogenolysis in the liver) becomes an important fuel source
What is fat used for exercise stored as?
Triglycerides in adipocytes
What are adipocytes?
fat tissues
True or false, the role of fat as an energy source is determined by its availability to the muscle cell?
true
What must triglycerides first be broken into for it to be metabolized and what is the process used called?
They must be broken into free-fatty-acids and glycerol via lipolysis.
Once Triglycerides have been broken into FFAs, what are they further converted to before entering the Kreb’s cycle?
They are converted to Acetyl Coenzyme A AKA Acetyl-CoA.
During low-intensity exercise, what is the primary fuel source from fat?
the circulating FFAs from adipocytes
The metabolism of _______ _______ increases alongside exercise intensity (fat.)
muscle triglycerides
When the VO2 Max reaches 65-85%, where does fast as a muscle energy source come from?
It comes equally between plasma FFAs and muscle triglycerides
At the beginning of exercise, plasma FFAs and muscle triglycerides are equally used, but what happens are duration increases?
There is a progressive rise in plasma FFAs used for fuel
During long-duration and low-intensity exercise, blood epinephrine levels rise and promote what process?
lipolysis
What is lipolysis?
Lipolysis is the process by which fats are broken down in our bodies through enzymes and water, or hydrolysis
What must protein be converted to before being used as energy and supplied to muscles?
amino acids
True or false, once converted, amino acids are supplied to the muscle tissue from the fiber’s own blood and amino acid pool?
true
True or false, skeletal muscle cannot directly metabolize certain amino acids to produce ATP?
False - they can
What is a fundamental different between glucose found in muscles vs glucose found in liver cells?
Muscle glucose is trapped within the cell and is not able to be released for circulation
During exercise, how can glucose stored within the inactive muscle be delivered to the exercising muscle?
via the glucose-alanine pathway
In the non-exercising muscles, what is glucose partially metabolized to and what does that manufacture?
it is partially metabolized to pyruvate to manufacture the amino acid Alanine.
Where does Alanine travel to once manufactured in a non-exercising muscle? And what happens next?
It travels to the liver where the amino group is removed and pyruvate is re-converted back to glucose to be released to the exercising muscle.
During prolonged endurance exercise, amino acids are freed from their parent proteins, what does this cause a spike in?
in the skeletal muscle amino-acid pool
What does a spike in the skeletal muscle amino-acid pool result in?
a small increase in the use of amino acids for fuel for exercise
What does the increased conversion of amino acids to glucose during exercise help to prevent?
Hypoglycemia and the oxidation of certain amino acids that can provide energy for muscular contraction
True or false, only one of the 3 different energy groups works at one time to produce ATP.
False - whilst there are 3 different energy systems, they work at the same time and one of them will dominante at specific times.
What is the dominant energy system at the onset of exercise?
phosphagen
What is the dominant energy system during endurance activities (but prior to achieving steady state)?
fast glycolytic (lactate) system
What is the dominant energy system during exercise in which the intensity approaches anaerobic threshold?
fast glycolytic (lactate) system
What is the dominant energy system during endurance activities after the anaerobic system has fatigued?
aerobic/oxidative system
Lactate is both used in ______________ in the liver and as a direct fuel source for _______ ________ and heart.
gluconeogensis
skeletal muscle
Where is lactate that is produced by skeletal muscles during exercises transported to? And what happens next?
It is transported to the liver via the blood and converted back to glucose to then be released back into the blood for transport back to the active skeletal muscles for ATP production.
What is the cori cycle?
the cycle of lactate-to-glucose between the muscle and liver.
What does the Cori Cycle preserve to do?
the Cori Cycle works to preserve the body’s blood glucose levels and ensures the muscles have adequate fuel to perform.
What energy systems are dominant between 0-30 seconds, 20-120 secs and 110-150+ secs of exercise?
0-30 seconds Phosphagen
20-120 anaerobic glycolysis
110-150+ aerobic/oxidative
What is a diabetic client MOST likely to experience if he or she takes too much insulin prior to an exercise session?
Hypoglycemia
