Metabolism

Question 1

What are the different energy substrates?

Answer 1

• Carbohydrate
• Fats
• Protein
• ATP
• Oxidative system
• ATP- PCr system
• Glycolytic system
• Oxidative system

Question 2

What are the 3 types of ATP users and what roles do they play?

Answer 2

• Myosin ATPase: All cross bridges locked in rigour conformation, no force generation, no lengthening
• Na+ - K+ ATPase: Cannot maintain resting membrane potential, cells swells and rupture, Ca+ ATPase- no force production/ fatigue

Question 3

What are the 3 types of ATP synthesis pathways and what roles do they play?

Answer 3

• ATP- Pcr system: Creatine kinase reactions- anaerobic met. Rapid (3-15 seconds), Anaerobic, substrate-level metabolism. Because ATP stores are very limited, this pathway is used to reassemble ATP. Pcr: ATP recycling; PCr energy cannot be used for cellular work. Replenishes ATP stores during rest and recycles ATP during exercise until used up.
• Glycolytic system: 2 versions: anaerobic and aerobic glycolysis, both breaks down of glucose to pyruvic acid, Anaerobic, break down of 6 C molecule (glucose) to a 3 (molecule), 10 chemical reactions in the cell cytoplasm. For 1 molecule of glucose; uses 2 molecules of ATP, resynthesis of 4 molecules of ATP, net gain of 2 ATP- 15 seconds to 2 minute.
• Oxidative system: Aerobic, ATP yield dependent on substrate. Duration: Steady supply for hours, in mitochondria not cytoplasm involving: Krebs cycle and electron transport chain.

Question 4

What are the pros and cons for the Glycolytic system?

Answer 4

Cons:
- low ATP yield, ineffective use of substrate
- Lack of 02 converts pyruvic acid to LA
- LA acid impairs glycolysis, muscle contraction
Pros
- Allows muscles to contract when O2 limited
- Permits shorter term, higher intensity exercise than oxidative metabolism can sustain

Question 5

What role does carbohydrate play?

Answer 5

• All carbohydrates converted to glucose
  
  • 4.1 kcal/g
  • Primary ATP substrate for muscles, brain
  • Extra glucose stored as glycogen in liver, muscles
• Glycogen converted back to glucose when needed to make more ATP
• Glycogen stores limited (2500 kcal): dietary carbohydrate needed in order to replenish

Question 6

What role does Fat play?

Answer 6

• Efficient substrate, efficient storage
  - 9.4 kcal/g
  - 70,000 + kcal stored in the body
• Energy substrate for prolonged, less intense exercise
  - Yields substrate for prolonged, less intense exercise

Question 7

What role does Fat play?

Answer 7

• Efficient substrate, efficient storage
  - 9.4 kcal/g
  - 70,000 + kcal stored in the body
• Energy substrate for prolonged, less intense exercise
  - Yields substrate for prolonged, less intense exercise
  - Must be broken down into FFA’s of glycerol
  - Only FFA’s are used to make ATP

Question 8

What role does Protein play?

Answer 8

• Energy substrate during starvation
  - 4.1 kcal/g
  - converted into glucose (glucogenesis)
  - conversion into FFA’s (lipogenesis)
  - For energy storage
  - For cellular energy substrate

Question 9

What role does ATP play?

Answer 9

• ATP stored in small amounts until needed (5-6 mol/kg at rest)
  eg. Max sprint at 900 W (300% VO2 max)
  Rate of ATP use= 3.7 mmol ATP /kg/s 2 seconds
  Sub-max exercise at 200 W (75% VO2 max)
  Rate of ATP use= 0.4 mmol ATP /kg/ s 15 seconds
• Break down of ATP to release energy
  
  • ATP+ water+ ATPase = ADP + Pi + energy
• Synthesis of ATP from by-products
  
  • ADP + Pi energy= ATP
  • Can occur in either absence or presence of O2