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Flashcards in Lecture 6 Deck (26)

What are the main carbohydrate fuels for contracting skeletal muscles?

Muscle glycogen and blood glucose are the major carbohydrate fuels for contracting skeletal muscle.


How are Muscle Glycogenolysis, muscle glucose uptake, CHO oxidation and liver glucose output influenced by exercise?

They are influenced by the intensity and duration of exercise.


How is muscle glycogenolysis maintained?

Muscle glycogenolysis is regulated by local and hormonal factors


How is the regulation of the liver output of glucose?

Liver glucose output is regulated by redundant controls; this ensures that optimal function is maintained.


What does training make the body consume for energy?

Training reduces reliance of the body on carbohydrates and instead directs metabolism to rely on fatty acid oxidation


How is glycogen broked down?

glycogen phosphorylase breaks down glycogen


What happens to lactate after it is produced?

lactate leaves the muscle but it can be taken up and converted to pyruvate and oxidised


What happens to glucose when it is phosphorylated?

Hexokinase phosphorylates glucose which is irreversible meaning the glucose is destined to be metabolised as soon as it's phosphorylated by hexokinase.


How does an increase in exercise intensity influence muscle glycogen breakdown?

With increase in exercise intensity an increase in glycogen breakdown follows. At high intensity this glycogen is broken down to lactate


How is glycogen breakdown influenced by duration of exercise?

glycogen breakdown decreases with duration of exercise


What are the main factors regulating glycogenolysis?

Ca2+ (calcium activates glycogen phosphorlyase) and Pi (lots of ATP breakdown means more breakdown desired)
Adrenaline (High levels mean high intensity exercis)


What are other factors regulating glycogenolysis?

More glycogen in the muscle increases glycogen breakdown.
Free Fatty Acid reduction can increase glycogenolysis and vice versa
High temperature increases adrenaline meaning more glycogen is broken down.


What does training do to glycogen breakdown and anaerobic respiration?

Training reduces glycogen breakdown at a given intensity. It also reduces anaerobic respiration.


What factors effect glucose uptake?

Glucose uptake increases with an increase in intensity and with duration.


How is glucose uptake regulated?

Glucose uptake is limited by rate of diffusion which is affected by:
Blood glucose concentration
Amount of receptors
Blood flow
Metabolic rate


How do glycogen levels affect glucose uptake?

More glycogen = Less glucose uptake


Is insulin necessary for glucose uptake during exercise?



What is the effect of adrenaline on glucose uptake?

No known effect of adrenaline on glucose uptake


How are liver glucose output and glucose uptake by muscles related?

Liver glucose output is closely matched with glucose uptake this is to maintain stable levels of glucose in the blood. This effect falls with duration.


Does gluconeogenesis occur in exercising muscles?

During exercise gluconeogenesis only happens in the liver.
**** needs verifying ****


Interesting Fact

1 hour of exercise drops glycogen by about 50%


What happens to liver gluconeogenesis during exercise?

When liver is low on glycogen it increases gluconeogenesis.


What substrates can be used for gluconeogenesis?

Amino acids, glycerol, pyruvate, and lactate can be used to produce more glycogen by gluconeogenesis


What factors are involved in the regulation of liver glucose output during exercise?

Feedforward and feedback mechanisms (liver output increases in anticipation of exercise)
Insulin & glucagon
sympathetic nerves
Liver glycogen (more glycogen = more release of glycogen into the blood)
Blood glucose (if glucose enters the body via gut then liver doesn't need to release glucose either)


How does training affect glucose uptake, oxidation and gluconeogenesis?

After becoming trained there is a reduction in glucose uptake at a given exercise intensity. A reduction in glucose oxidation follows. Gluconeogenesis is also reduced.


What happens to PDH activity with increased intensity and duration of exercise?

Increase in exercise intensity there is an increase in PDH activation. With duration PDH activity decreases due to lower dependence on carbohydrate metabolism.