Bioenergetics
What is bioenergetics?
The study of how energy is captured, transferred, and utilized in biological systems
Where is ~95% of the body’s creatine stored?
Skeletal muscle
What is another name for the immediate energy system?
The phosphagen system
Where does the Krebs cycle occur?
In the mitochondria
Where does the ETC occur?
Inner mitochondrial membrane
What is the primary energy currency in the body?
Adenosine Triphosphate
What is the enzyme that catalyzes the ATP resynthesis reaction using phosphocreatine?
Creatine Kinase
What molecule donates a phosphate to regenerate ATP during maximal effort?
Phosphocreatine (PCr)
What molecule must acetyl-CoA combine with to enter the cycle?
Oxaloacetate
How many ATP are formed per NADH vs. per FADH₂?
NADH = 3 ATP; FADH₂ = 2 ATP
Name two byproducts of macronutrient catabolism in addition to ATP.
CO₂ and H₂O
What performance adaptations are commonly seen with creatine supplementation?
↑ strength, ↑ lean body mass, ↑ anaerobic exercise capacity
What is the normal ratio of ATP to ADP in resting muscle?
Greater than 40:1
How many NADH and FADH₂ are produced per turn of the cycle?
3 NADH and 1 FADH₂
What is the role of oxygen in the ETC?
It is the final electron acceptor, forming water
Rank immediate, short-term, and long-term ATP resynthesis in terms of duration.
Immediate: 1–5 sec; Short-term: ~2 min; Long-term: >2 min
What is the typical percentage increase in muscle creatine stores with supplementation?
10–40%
What are the two main enzymes driving ATP resynthesis in the phosphagen system?
Creatine kinase & adenylate kinase (or myokinase)
What vitamin-derived cofactors are needed for NAD⁺ and FAD?
Niacin (NAD⁺) and Riboflavin (FAD)
What hypothesis explains how ATP is formed via proton gradients in the ETC?
The chemiosmotic hypothesis
Why is understanding ATP resynthesis essential for nutrition decisions in athletes?
To match metabolic demands with diet and avoid harming performance
What is the main myth about creatine disproven by research?
That it causes dehydration, hair loss, cramps, or kidney damage
What is the starting and end product of glycolysis?
Starts with 1 glucose (or glycogen), ends with 2 pyruvate (or lactate under anaerobic conditions)
What is the primary function of the Krebs cycle in energy metabolism?
To remove hydrogens/electrons and transfer energy to NADH & FADH₂ for the ETC
Why does oxidative phosphorylation stop without oxygen?
Because electrons cannot flow through the ETC without oxygen as the terminal acceptor