ES - Bioenergetics and Metabolism - Characteristics of Energy Systems

Question 1

Explain ATP-PCr (Phosphagen) energy system.
Relies on?
Enzyme?

Answer 1

Provides ATP primarily for short-term, high intensity activities (resistance training, sprinting) and is highly active to at start of all exercises regardless of intensity,

Relies on hydrolysis of ATP and breakdown of another high-energy phosphate, Creatine Phosphate (CP)

Enzyme that catalyzes the synthesis of ATP from CP and ADP is Creatine Kinase.

Question 2

ATP-PCr equation

Answer 2

ADP + CP ATP + Creatine

CP supplies phosphate group that combines w/ ADP to replenish ATP.

Question 3

Under what volume and intensity conditions would ATP-PCr contribute the most to energy demands?

Answer 3

Volume: 0-6s
Intensity: Extremely high
Rate of ATP production: Fast

Question 4

Amount of ATP in body stores

Answer 4

approx. 80-100g (~3 oz) at any given time.
Cannot be completely depleted (req. for basic cell functions)
Decrease up to 50%-60% of pre-exercise levels during exercise.
Type II fibers have more higher concentration of CP than Type I.

Question 5

Glycolytic energy system.

Enzyme?

Answer 5

breakdown of carbs, either glycogen stored in muscle or glucose delivered in blood, to resynthesize ATP.
Involves multiple enzyme catalyzed reaction, so ATP resynthesis is not as rapid as w/ single-step ATP-PCr. However, the capacity to produce ATP is much higher due to a larger supply of glycogen and glucose compared to CP.

Enzyme: lactate dehydrogenase

Question 6

Adenylate Kinase Reaction to replenish ATP

Answer 6

aka Myokinase
2ADP ATP + AMP
AMP is also a powerful stimulant of glycolysis

Question 7

2 directions to glycolysis after pyruvate is established

Answer 7

Anaerobic: Pyruvate converted to lactate in sarcoplasm.
Aerobic: Pyruvate shuttle into mitochondria to undergo Krebs cycle.

Question 8

Anaerobic Glycolysis (Fast)

Answer 8

End product is pyruvate. From there:
pyruvate is converted to lactate, resulting in faster ATP resynthesis via rapid regeneration of NADH+. However, it’s limited in duration b/c of subsequent H+ production and resulting decrease in cytosolic pH.

At higher intensity exercise (e.g. resistance training), pyruvate and NADH will increase above what can be handled by pyruvate dehydrogenase and will then be converted into lactate and NAD+.

Question 9

Anaerobic Glycolysis equation

Answer 9

Glucose + 2Pi + 2ADP —> 2Lactate + 2ATP + H2O

Question 10

Aerobic Glycolysis (Slow)

Answer 10

when the resultant pyruvate is shuttled into mitochondria to undergo Krebs cycle.
ATP resynthesis rate is slower b/c of numerous reactions, but can occur for a longer duration if exercise intensity is low enough.

If energy demands are lower and oxygen is present in sufficient quantities in cell, pyruvate can be further oxidized in mitochondria.

Question 11

Under what volume and intensity conditions would glycolytic energy system contribute the most to energy demands?

Answer 11

Volume: 6s-3min
Intensity: very high-moderate
Rate of ATP production: Fast=2, Slow=3

Question 12

Cause of fatigue during glycolysis

Answer 12

aka Metabolic Acidosis
Lactate is not the cause.
Proton (H+) accumulation during fatigue reduces intracellular pH, inhibits glycolytic reactions, and directly interferes w/ muscle’s excitation-contraction coupling; possibly by inhibiting Ca binding to troponin or by interfering w/ crossbridge recycling.

Question 13

Lactate as an energy substrate

Answer 13

used as energy in Type I and cardiac muscle fibers

Used in formation of glucose form non-carb sources (gluconeogenesis) during extended exercise and recovery.

Question 14

Concentrations of blood lactate at different stages of rest and exercise

Answer 14

Normal range in blood at rest: 0.5-2.2 mmol/L
Wet muscle: 0.5-22 mmol/kg of wet muscle
Severe fatigue during exercise may occur at: 20-25 mmol/L

Question 15

Lactate and exercise intensity and rate of lactate production

Answer 15

Increases depending on exercise intensity, muscle fiber type, exercise duration, training status, and initial glycogen levels.

Maximal rate of lactate production for:
Type II fibers: 0.5 mmol.g.s
Type I fibers: 0.25 mmol.g.s

Question 16

Cori Cycle

Answer 16

the process of transporting lactate in the blood to the liver, where it’s converted to glucose.

Question 17

Blood lactate concentrations normally return to pre-exercise levels within…
Passive v. Active recovery on lactate clearance…
Peak blood lactate occurs when?

Answer 17

1 hour after activity, depending on the duration and intensity of the exercise, training status, and type of recovery (passive v. active).

Light post-exercise activity increase lactate clearance rates
ex. 200y maximal-effort swim resulted in greater clearance than a passive recovery in competitive swimmers.

Peak blood lactate concentrations occur approx. 5 minutes after exercise completion, a delay attributed to time required to buffer and transport lactate from tissue to blood.

Question 18

Glycolysis Leading to Krebs

Answer 18

if oxygen is sufficient in mitochondria, pyruvate is not converted to lactate; it’s transported to mitchondria along w/ reduced (H+ added) 2NADH.
When pyruvate enters mitochondria, it’s converted into acetyl-CoA by pyruvate dehydrogenase complex, resulting in loss of carbon as CO2.
Acetyl-CoA can then enter Krebs for further ATP resynthesis. NADH enter ETC to also be used to resynthesize ATP.

Question 19

Aerobic Glycolysis equation

Answer 19

Glucose + 2Pi + 2ADP + 2NADH+ —> 2Pyruvate + 2ATP + 2NADH + H2O

Question 20

2 primary mechanisms for resynthesizing ATP during metabolism

Answer 20

Substrate-level Phosphorylation

Oxidative Phosphorylation

Question 21

Phosphorylation

Answer 21

process of adding an inorganic phosphate (Pi) to another molecule
ex. ADP + Pi + —> ATP is phosphorylation of ADP to ATP

Question 22

Oxidative Phosphorylation

Answer 22

resynthesis of ATP in the ETC.

Question 23

Substrate-level phosphorylation

Answer 23

the direct resynthesis of APT from ADP during single reaction in metabolic pathways.

Question 24

2 steps in glycolysis that result in substrate-level phosphorylation of ADP to ATP.

Answer 24

1,3 bisphosphatglycerate + ADP + Pi —-Phosphoglycerate—> 3-phosphoglycerate + ATP

Phosphoenolpyruvate + ADP + Pi —Pyruvate kinase—> Pyruavte + ATP

Question 25

Number of ATP resyntehsized during glycolysis from blood glucose and muscle glycogen

Answer 25

BG: 4
MG: 3

Question 26

Role of the glycolysis regulatory enzymes: hexokinase, PFK, and pyruvate kinase

Answer 26

Hexokinase: catalyzes the phosphorylation of glucose to glucose-6-phosphate. Is allosterically inhibited by increasing concentrations of glucose-6-phosphate in sarcoplasm.

PFK: commits the cell to metabolize glucose rather store it as glycogen. As ATP concentrations increase, PFK activity decreases, which decreases conversion of fructose-6-phosphate to fructose 1 ,6-phosphate, thus decreasing glycolytic pathway.

Pyruvate kinase: allosterically inhibited by ATP and acetyl-CoA and activated by high concentrations of AMP and fructose-1, 6-biphosphate.

Question 27

Lactate Threshold
Def?
Corresponds w/?
Begins at % of O2 uptake for untrained and trained?

Answer 27

exercise intensity or relative intensity at which blood lactate begins an abrupt increase above baseline concentrations.Represents significant increased reliance on anaerobic mechanisms for energy production.
Corresponds well w/ ventilatory threshold (breaking point in relationship between ventilation and VO2).
Typically begins at 50%-60% of maximal O2 uptake in untrained and at 70%-80% in aerobically trained.

Question 28

Onset of blood lactate accumulation (OBLA)

Answer 28

second increase in rate of lactate accumulation at higher levels of intensity when blood lactate concentration reaches 4 mmol/L.

Question 29

Training near or above LT or OBLA pushes the LT or OBLA curve to the?

Answer 29

Right b/c lactate accumulation. occurs later at higher intensifies (i.e. higher VO2).
This shift probably occurs as a result of changes in hormone release, like reduced catecholamine release at higher exercise intensities and increased mitochondrial content that allows for grater production of ATP thru aerobic mechanisms.

Question 30

Oxidative (Aerobic) System
Fuels?
Protein use?

Answer 30

primary source of ATP during lower intensity exercises using primarily carbs and fats as substrates.
Protein for energy increases during longer bouts of starvation (>90 min. of exercise).

Question 31

Substrates uses at different intensities

Answer 31

ATP produced at Rest: ~70% fats, 30% carbs.
Onset of activity: shift from fats to carbs
High intensity aerobic exercise: 100% carbs, minimal fats and protein usage.
Prolonged, sub-max, steady-state: gradual shift from carbs to fats. Very small extent of protein usage.

Question 32

Glucose and Glycogen Oxidation

Answer 32

If 02 is preset is sufficient quantities, the end product of glycolysis (pyruvate) isn’t converted to lactate but is transported to mitochondria, where it’s converted to acetyl-CoA, which enters Krebs.

Question 33

Fat Oxidation

Answer 33

Triglycerides stored in fat cells can be broken down by an enzyme, hormone-sensitive lipase, to produce FFA and glycerol.
FFAs enter mitochondria, where they undergo beta-oxidation (FFAs are broken down, resulting in acetyl-CoA and hydrogen protons).
Acetyl-CoA enters Krebs directly which hydrogen atoms are carried by NADH and FADH2 to ETC.
Results in hundreds of ATP molecule (1 triglyceride = 300+ ATP).

Question 34

Protein Oxidation

Answer 34

broken down into amino acids, which can further be converted into glucose (gluconeogenesis), pyruvate, or various Krebs intermediates to produce ATP.
Minimal contributions during short-term exercise but may contribute 3%-18% of energy req. during prolonged activity.

Question 35

Effect of Event Duration and Intensity on Primary Energy System Used
Duration - Intensity - Primary energy system

Answer 35

0-6s - extremely high - phosphagen system
6-30s - very high - phosphagen and fast glycolysis
30s-2min - high - fast glycolysis
2-3 min - moderate - fast glycolysis and oxidative system
>3 min - low - oxidative system

Question 36

Rankings of rate and capacity of ATP production

System - Rate of production - Capacity of Production

Answer 36

*System - Rate of production - Capacity of Production
*1= fastest/greatest, 5=slowest/least
Phosphagen - 1 - 5
Fast glycolysis - 2 - 4
Slow glycolysis - 3 - 3
Oxidation of carbs - 4 - 2
Oxidation of fats - 5 - 1

Question 37

Under what volume and intensity conditions would the aerobic energy system contribute the most to energy demands?

Answer 37

Volume: >3 min
Intensity: Low