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Flashcards in Lecture 22 Deck (16)

What is de novo synthesis?

De novo synthesis is the synthesis of non-essential amino acids.


How is oxidation of amino acids measured?

Stable isotopes can be used to measure oxidation of amino acids using 13C labelled amino acids.


What results can be used to understand protein metabolism?

Ratio of 13CO2/12CO2 in breath and labelled/unlabelled amino acids in plasma.

More 13C in breath means more oxidation of infused tracer.


What happens to muscle protein synthesis during exercise?

Decrease of protein synthesis occurs during exercise.


What is the normal turnover rate in muscles? Is this a high value?

Turnover rate is typically 1-2% per day in muscles. This turnover is high in absolute terms due to amount of protein in muscle.


What happens during exercise and post exercise to explain the changes that occur in muscle size?

During exercise protein degradation is higher than protein synthesis but after exercise in resting periods protein synthesis increases significantly more than degradation rate.


How does endurance exercise affect untrained athletes?

Endurance exercise does not stimulate myofibrillar hypertrophy in untrained athletes but it does in trained athletes.


How does resistance training affect untrained athletes?

both myofibrillar and mitochondrial hyertrophy occurs in untrained athletes that do resistance training


How does endurance training affect trained athletes?

>mitochondrial hypertrophy

no change in myofibrillar hypertrophy


How can a muscle building stimulus increase protein synthesis?

Stimulus increases transcription of certain genes and mRNA.

improvement in translation efficiency can increase protein synthesis.


Why are Eif3s and Eif4s used when determinin muscle protein synthetic rate?

Eif3s and Eif4s are factors of translation initiation and researchers look for these to measure translation initiation.


What kind of effect does S6K1 have?

Effect of exercise on S6K1 is fibre-type specific. (Type 2 hypertophy)


Why does activity of the mTOR pathway decrease during exercise?

AMPK activity increases during exercise


What does rapamycin administration in humans do to skeletal muscle protein synthesis?

rapamycin administration in humans blocks contraction-induced increase in skeletal muscle protein synthesis.


Why does sarcopenia occur?

Protein synthetic response is reduced in elderly.

Aging causes a loss of muscle and increase in fat mass

activity of mTOR is essential for anabolic response to exercise and in elderly the effect of mTOR is decreased.


What happens to cancer patients after food intake?

The increase in protein synthesis after food intake is blunted in cancer patients.