Chapter 3 Bioenergetics of Exercise and Training Flashcards
What are exergonic reactions?
Energy releasing reactions and are generally catabolic
What are endergonic reactions?
Require energy and include anabolic (build up) and the contraction of muscle
What are the Anaerobic energy processes?
Phosphagen and Glycolytic
What are the 3 Aerobic energy processes?
Krebs Cycle, Electron Transport Chain and Oxidative system
What is the final chemical action during hydrolysis of ADP?
The hydrolysis of ADP breaks the terminal bond, releases energy and leaves AMP, P and H+
The replenishment of ATP in human skeletal muscle is accomplished by three basic energy systems
Phosphagen, glycolytic, and oxidative
T/F Are all three energy systems active during at any given time?
TRUE. All three energy systems are active at any given time; however the magnitude of the contribution of each system to overall work primarily dependent on the intensity of the activity and secondarily on the duration.
What is the chemical process during the phosphagen energy system?
ADP + CP»_space;»>««
The Creatine Kinase Reaction
Provides energy at a high rate; however, because CP is stored in relatively small amounts the phosphagen system cannot be the primary supplier of energy for continuous, long duration activities.
How much ATP can the body store at any given time?
80-100g (about 3 ounces) which does not represent a significant energy reserve for exercise. In addition, ATP stores cannot be completely depleted due to the necessity for basic cellular function.
What enzyme is powerful enough to stimulate Glycolysis?
Adenylate Kinase also called Myokinase
The reactions of the phosphagen system are largely controlled by?
The Law of Mass Action or the Mass Action Effect
The law of mass action states
That the concentrations of reactants or products (or both) in solution will drive the direction of the reactions.
What is Glycolysis?
Glycolysis is the breakdown of carbohydrate (sugar)-either glycogen stored in the muscle or glucose delivered in the blood to resynthesize ATP.
Why does glycolysis produce ATP at a slower rate compared to the phosphagen system?
The process of glycolysis involves multiple enzyme dependent reactions
During Glycolysis the capacity to make is much higher due to ?
A larger supply of glycogen and glucose compared to CP
Where does phosphagen and glycolysis take place?
In the sarcoplasm of the cell
What is the end result of glycolysis
Pyruvate
What are the two directions that pyruvate can proceed
1) Pyruvate can be changed to lactate in the sarcoplasm
2) Pyruvate can be shuttled into the mitochondria
Anaerobic Glycolysis
When Pyruvate is converted to lactate, ATP resynthesis occurs at a faster rate via the rapid regeneration of NAD+, but is limited in duration due to the subsequent H+ production and resulting decreases in pH
Aerobic/ Slow Glycolysis
The ATP resynthesis rate is slower because of the numerous reactions, but can occur for a longer duration if the exercise intensity is low enough.
The fate of pyruvate is ultimately controlled by
the energy demands within the cell.
The formation of lactate from pyruvate is catalyzed by the enzyme _______ ________
Lactate Dehydrogenase
Proton H+
accumulation during fatigue reduces the intracellular pH, inhibits glycolytic reactions and directly interferes with muscle excitation -contraction coupling-possibly by inhibiting calcium binding to troponin
Metabolic Acidosis
The process of an exercise induced decrease in pH
Why doesn’t lactate cause Metabolic Acidosis
Lactate is utilized as an energy substrate, specifically in type 1 and cardiac fibers. It is also used during the formation of glucose from non carbohydrate sources during extended exercise and recovery. The process is called Glyconeogenesis
Cori Cycle
Lactate can be cleared by oxidation with the muscle fibers in which it was produced, or it can be transported in the muscle fibers to be oxidized. Lactate can also be transported in the blood to the liver, where it is converted to glucose.
Blood Lactate Concentration Levels
Return back to normal, pre-exercise values within an hour after activity, depending on the duration and intensity of exercise, training status, and type of recovery.
Net reaction for glycolysis
Glucose +2Pi + 2ADP»_space;»> 2Lactate +2ATP +H2O
Net reaction for Pyruvate
Glucose +2Pi +2ADP + 2NAD+»_space;»> 2 Pyruvate +2ATP +2NADH + 2H2O
Two primary mechanisms for resynthesizing ATP during Metabolism
1) Substrate-level phosphorylation
2) Oxidative phosphorylation
Phosphorylation is the process of adding an ___________ ___________ to another molecule
Inorganic Phosphate
Oxidative Phosphorylation
refers to the resynthesis of ATP in the Electron Transport Chain
Substrate Level Phosphorylation
refers to the direct resynthesis of ATP from ADP during a single reaction in the metabolic pathways.
Step 1 for substrate level phosphorylation
Step 2 for substrate level phosphorylation
S1) 1,3-bisphosphoglycerate + ADP + Pi»»»»»3-phosphoglycerate +ATP
S2) Pi»»»»Pyruvate + ATP
The gross number of ATP molecules that are resynthesized as a result of substrate-level phosphorylation during glycolysis is ___
4
The enzyme that converts fructose-6-phosphate to fructose -1,6-biphosphate
phosphofructokinase (PFK)
Which enzyme is responsible for the phosphorylation of blood glucose
Hexokinase
Two sources of glucose
Blood Glucose and Muscle Glycogen
Blood Glucose and Muscle Glycogen ATP Resynthesized
(BG)- 2 ATP are used and 4 ATP are resynthesized which results in a net resynthesis of 2 ATP molecules.
(MG)- Only 1 ATP is used and 4 ATP are resynthesized, which yields a net resynthesis of 3 ATP molecules
is stimulated to increase during intense muscle actions by high concentrations of ADP, Pi and ammonia and by a slight decrease in pH and AMP, all of which are signs of increased ATP hydrolysis and a need for energy
Glycolysis Stimulation
It is inhibited by markedly lower pH, ATP, CP, citrate and free fatty acids
Glysolysis Inhibition
Concentrations of Hexokinase, PFK and Pyruvate kinase. All three are regulatory enzymes in glycolysis, because each has an important allosteric (other site) binding sites.
Glycolysis regulation
Occurs when the end product of a reaction or series of reactions feeds back to regulate the turnover rate of key enzymes in the metabolic pathways.
Allosteric Regulation
Occurs when an end product binds to the regulatory enzyme and decreases it’s turnover rate and slows product formation
Allosteric Inhibition
Occurs when an “activator” binds with the enzyme and increases it’s turnover rate.
Allosteric Activation
Is the most important regulator of glycolysis because it is the rate limiting step.
Phosphofructokinase
Is an allosteric inhibitor of PFK; therefore, as intracellular ATP concentrations rise, PFK activity decreases and reduces the conversion of fructose 6 phosphate to fructose 1,6-biphosphate and, subsequently, decreases activity of the glycolytic pathway.
Adenosine Triphoshate
The exercise intensity or relative intensity at which blood lactate begins an abrupt increase above the baseline concentration has been termed the
Lactate Threshold
The ______ _______ represents a significantly increased reliance on anaerobic mechanisms for energy production to meet demand.
Lactate Threshold
The Lactate Threshold begins at ___ - ____ for Untrained individuals
50%-60%
The Lactate Threshold begins at ____ -____ for aerobically trained individuals
70%-80%
A second increase in the rate of lactate accumulation
onset of blood lactate accumulation (OBLA). Occurs when the concentration of blood lactate reaches 4 mmol/L
This system utilizes carbohydrates and fats as substrates
Oxidative System (>90 minutes of exercise)
At rest
70% of ATP is derived from fats and 30% from carbohydrate
The end product of Glycolysis when oxygen is sufficient, Pyruvate is
Transported to the Mitochondria
A series of reactions that continues the oxidation of the substrate from glycolysis and produces 2 ATP indirectly from guanine triphosphate (GTP)
Krebs Cycle
These molecules transport hydrogen atoms to the Electron Transport Chainto be used to produce ATP from ADP.
6 Molecules of NADH and 2 Molecules of reduced Flavin Adenine Dinucleotide (FADH2)
During the Krebs Cycle the hydrogen atoms are passed down the chain to form a proton concentration gradient, which provides the energy for ATP production, which oxygen serving as the final electron acceptor
A series of electron carriers known as Cytochromes
One molecule of NADH can produce
3 Molecules of ATP
One molecule of FADH can produce 3 molecules of ATP
2 Molecules of ATP
Krebs Cycle and Electron Transport Chain result in the production of ________ATP from the breakdown of one blood glucose molecule
38
If the initiation of glycolysis is muscle glycogen the net ATP production is ____, since the hexokinase reaction is not necessary with muscle with muscle glycogenolysis.
39
Triglycerides stored in fat cells can be broken down by an enzyme, hormone sensitive ______ to produce free fatty acids and glycerol.
Lipase
Beta Oxidation
Free fatty acids entering the mitochondria
Beta Oxidation
Hundreds of ATP molecules are produced
Leucine, Isoleucine, Valine
Branched Chain Amino Acids
Conversion of Isocitrate to a-ketoglutarate, a reaction catalyzed by the enzyme
isocitrate dehydrogenase
isocitrate dehydrogenase
Is stimulated by ADP and and allosterically inhibited by ATP
During exercise, the degree which anaerobic and oxidative systems contribute to the energy being produced is determined primarily by _______ _______ and secondarily by ______ _________
Exercise Intensity
and Exercise Duration
Energy Substrates
Molecules that provide starting materials for bioenergetic reactions, including phosphagens (ATP and CP) glucose, glycogen, lactate free fatty acids and amino acids
Post Exercise phosphagen repletion can occur in relatively short period; complete resynthesis of ATP appears to occur within ____ to ____ minutes and complete CP resynthesis can occur within ____minutes
3 to 5 minutes
8 minutes
Repletion of phosphagens is largely accomplished as a result of _____ ________ although glycolysis can contribute to recovery after high-intensity exercise.
Aerobic Metabolism
Glycogen Storage
300- 400 g of glycogen are stored in the body’s total muscle
70-80 g of glycogen are stored in the liver
The rate of glycogen depletion is related to _______ _______
Exercise Intensity
Post exercise glycogen repletion
Optimal if 0.7 to 3.0 of carbohydrate per kilogram of body weight is ingested every 2 hours following exercise
Is a measure of a person’s ability to take in oxygen
Oxygen Uptake
At the start of an exercise bout, however, some of the energy must be supplied through anaerobic mechanisms because the aerobic system responds slowly to the initial increase in the demand for energy
Oxygen deficit
After exercise oxygen uptake remains above pre exercise levels for a period of time that varies according to the intensity and length of exercise
Oxygen debt or Excess post exercise oxygen consumption
The EPOC is the
Oxygen uptake above resting values used to restore the body to the pre exercise condition
Contributions from Anaerobic mechanisms are primary up to ___ seconds
60 seconds
_____ has the greatest effect on EPOC
Intensity
30 second maximum cycling with 4 minutes of recovery
1:8 work to rest ratio
Which substance can be metabolized anaerobically?
Glucose
Which is the primary cause of metabolic acidosis?
ATP»»»ADP + Pi + H+
Which of the following energy systems produces ATP at the quickest rate ?
Phosphagen
Approximately how many net ATP are produced via the oxidative energy system from the metabolism of one glucose molecule?
38
Which of the following energy substrates cannot be depleted during extreme exercise intensities or durations?
ATP
