APK 2105C Lecture Notes - Lecture 44: Creatine Kinase, Anaerobic Glycolysis, Oxidative Phosphorylation
Chapter 12, Lecture 5
Muscle Physiology
• Skeletal muscle metabolism
o The mechanism for producing ATP in a myocyte will vary depending on the type
and the intensity of work
o Capillaries supply the muscle with nutrients
▪ Glucose
▪ Fatty acids
o How is ATP made in skeletal muscle cell
▪ Varies on type of exercise and how hard you’re working (intensity)
• The creatine-phosphate (CP) system
o When ATP utilization increases
▪ ATP decreases
• ATP is not stored in our cells—there’s SOME on hand, but it’s
made on demand
▪ ADP increases
o Substrate-level and oxidative phosphorylation need a few seconds to get up to
speed to supply the needed ATP
o CP + ADP → ATP + creatine
▪ Rxn happens with creatine kinase
▪ Creatine kinase dephosphorylates the CP and attaches it to the ADP
▪ This ATP fuels the cell until the rest of cellular respiration can happen
• Metabolism changes with intensity
o Gradual shift from one predominating
system to another
o Light exercise vs. intense exercise
▪ Light exercise
• CP is used up
immediately
• Anaerobic glycolysis
and oxidative
phosphorylation starts
before CP ends
• There is a gradual shift
from 1 ATP source to
another
• Can do sub maximal
activity for a long time because we get more oxygen and we can
do oxidative phosphorylation longer
▪ Intense exercise
• CP is used up within the first minute
• Anaerobic glycolysis spikes a lot and then ends
• Gradual incline in oxidative phosphorylation
• Cannot do this type for a long time because anaerobic glycolysis
(main source of ATP) cannot continue for a long time
• Clinical correlation = energy systems and activities
o As duration increases, intensity has to come down
o Submaximal exercise can be maintained for a long time
▪ More aerobic mechanisms to maintain ATP needs
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