W2 - Anaerobic energy provision

Question 1

How is energy provided for cells?

What ATPase enzyme sits on myosin head(can only accept ATP to provide energy)

Answer 1

• ATP provides the chemical energy that can be converted into other forms of energy used by living cells
  
  • Energy for muscle contraction: ATP hydrolysed by myofibrillar ATPase
  • Myosin head becomes detached from the actin which releases energy (formation of ADP)

Question 2

Why is the regeneration of ATP important?

Answer 2

• ATP storage in the cell is very limited (~2 seconds worth of maximum contractions)
  
  • Body must constantly synthesise new ATP (if not: → Rigor mortis)
    –> NO ATP available causes myosin heads to stay attached to the actin

Question 3

What are the main ATP pathways?

Answer 3

• ATP-PCr system (anaerobic metabolism)
• Glycolytic system (anaerobic metabolism) → measured through lactate
• Oxidative system (aerobic metabolism) → measured through VO2/oxygen

Question 4

Describe the ATP-PCr system

Answer 4

Used in activities that need maximal muscle force production e.g.: weightlifter/sprinter
* ATP yield: 1 mol ATP per mol of substrate (PCr)
* Recycling ATP during exercise until used up (~3-15 s maximal exercise) ~ breakdown & resynthesis
* PCr energy cannot be used for cellular work BUT can be used to reassemble ATP

Question 5

Describe the relationship between creatine vs. exercise intensity

Answer 5

As exercise intensity increases, creatine content decreases as muscle phosphocreatine declines
–> Up to VO2Max, ATP is untouched (ATP can easily be replenished)
–> The more anaerobic resources used = lactate increase but PCr stores are lost
Both creatine kinase and Myokinase enzymes increase in anaerobic muscles

Question 6

What are some issues with using creatine as a supplement?

Answer 6

• PCr + ADP + H+ → Cr + ATP
  
  • ADP increases can be delayed
    – Cross-bridge cycling slowing improved
    – Osmotic activity of creatine: Higher cell water content → weight gain, attracts water causing the cell to increase in size and weight (potential reason why creatine is not excessively high in sprinters)

Question 7

Explain the Myokinase reaction that takes place during high intensity exercise

Answer 7

Only active when exercise intensity is very high (drop in pH which activates this reaction)
* ADP + ADP → ATP + AMP (at the cost of 31 kJ/mol ADP) - if exercise intensity is very high AMP is also high Limited capacity to produce ATP
* AMP is activator of enzymes involved in glycogen breakdown
* Only important during high intensity exercise (activated when pH falls)

Question 8

Describe what happens in the glycolytic system

Answer 8

• Breakdown of glucose/glycogen via glycolysis
  
  • Most frequently studied glycolytic enzymes are: phosphorylase, phosphofructokinase (PFK), and lactate dehydrogenase (LDH)
  • PFK and phosphorylase are essential to the anaerobic yield of ATP, training might enhance glycolytic capacity and allow the muscle to develop greater tension for a longer period of time.
  • ATP yield: 2 to 3 mol ATP per mol of substrate (glucose or glycogen, respectively) – or 1-1.5 mol ATP per mol of lactate if all pyruvate is converted to lactate
  • Breaking up glycogen already gives us a phosphorylized glucose molecule, which is why less ATP has to be invested into the breakdown of Glycogen
  • Duration: 15 s to 2 min

Question 9

What is the rate limiting enzyme in glycolysis?

What are the two rate limiting enzymes in the Krebs cycle?

Answer 9

Phosphofructokinase (PFK)

Citrate synthase
Succinate dehydrogenase

Question 10

How does PFK control the Glycolytic system?

Answer 10

glycolytic system –> better breakdown of glucose into pyruvate
–> Rate-limiting enzyme
* decrease ATP (increase ADP) → PFK activity increase
* increase ATP → PFK activity decrease
- Also regulated by products of Krebs cycle (increased products causes an increase in PFK)

Question 11

How does Creating Kinase control the ATP-PCr system?

Answer 11

controls rate of ATP production in ATP-PCr system
–> Negative feedback system:
* When ATP levels decrease (ADP increase), CK activity increase
* When ATP levels increase, CK activity decrease –> no need to regenerate ATP

Question 12

How far can you run from using energy only from…

1. PCr breakdown
2. Anaerobic Glycolysis
3. Oxidative Metabolism (glucose)
4. Oxidative Metabolism (fat)

Answer 12

= 100m
= 300m
= Half marathon
= approx. 1360km (170hrs at a slow jog)

Question 13

What test is used to determine peak power and fatigue index?

Answer 13

Wingate testing: anaerobic variables
* Wingate test (30-s all-out sprint) on cycle ergometer
* Applying the correct load (traditionally: ~7.5% of body mass)
* Determination of peak power, fatigue index

Question 14

What is the formula for fatigue index?

Answer 14

FI = (peak power-lowest power)/peak power * 100

Question 15

Where does the energy source come from during the Wingate test?

Answer 15

• This paper ESTIMATED PCr and glycolytic contribute. PCr was assumed to contribute 100% until peak power was achieved, then assumed to decline linearly until the 10-s point

Question 16

Name two reasons for the predominance of PCr-ATP metabolism and glycolysis early on in the Wingate test

Answer 16

• Fast energy ( many ATP molecules per time)
  
  • Metabolic Inertia ( aerobic metabolism slower to start “oxygen takes time to reach the muscle)

Question 17

What is the calculation of anaerobic energy contribution (“ATP turnover”) Through a muscle sample

Answer 17

-2(delta ATP) -1(delta ATP) + 1.5(delta Lactate) + 1.5(delta Pyruvate)