Mechanisms Flashcards
Glucose and monosaccharides circulate freely in the blood. What is a role of glucose?
Maintaining CHO oxidation in muscle.
Entry into cells facilitated by? Describe each.
Glucose transporters facilitate the transport of glucose across plasma membranes.
GLUT1 - ensures both RBC and brain gets adequate glucose levels.
GLUT2 - active when high levels of glucose in body (e.g. after eating).
GLUT3 - glucose transport in neurons.
GLUT4 - insulin regulated transport of glucose. Also most abdundant facilitative transporter in muscle.
SGLT1 - glucose re-absorption in kidney and intestine.
What is gluconeogenesis? Where does it occur?
Process of converting non CHO substrates (e.g. lactate) into glucose.
Occurs in liver and kidney.
Contributes to energy supply in post absorptive state.
What is glycogenesis?
If surplus glucose, metabolic flux through Kreb’s cycle is overwhelmed and ATP inhibits glycolysis.
What happens in the alanine-glucose cycle?
It is a series of reactions in which amino groups and carbons from muscle are transported to the liver.
When muscle degrades amino acids for energy needs, resulting nitrogen is transaminated to pyruvate to form alanine.
Alanine is shuttled to the liver, where the nitrogen enters the urea cycle and pyruvate is used to make glucose which is then taken to the rest of body.
Definition of gastric emptying?
Rate at which ingested foods are delivered to the small intestine and the extent to which they are modified by gastric secretions.
What is GI?
Measure of rate of digestion and absorption of CHO foods and the effect this has on blood glucose levels.
Study on GI?
Thomas et al. (1991):
Cyclists pedalled to exhaustion.
Those who ingested low GI pre exercise did best.
Because of slow release of glucose throughout exercise and there not being an insulin surge.
3 factors affecting CHO oxidation?
Exercise intensity - increased intensity = more CHO oxidation (levels off at 75% Vo2 max).
Muscle glycogen = lower levels of initial glycogen results in lower CHO oxidation.
Training - endurance training produces decreased reliance on CHO metabolism and increased fat metabolism.
