L34- Integration of Metabolism Flashcards
What is the preferred metabolic fuel for skeletal muscle at rest?
Fatty acids.
What is the preferred metabolic fuel for skeletal muscle at work?
Glucose.
What is the preferred metabolic fuel for the heart?
Fatty acids.
What is the preferred metabolic fuel for the brain?
Glucose (and ketone bodies during starvation).
Which type of enzymatic regulation typically involves a fast response that can change the concentration and activity of enzymes already present and functioning?
Allosteric regulation.
Addition or removal of a phosphate group to an enzyme is an example of what type of enzymatic regulation?
Covalent regulation.
What type of enzymatic regulation involves synthesis or degradation of enzymes?
Inducible enzyme regulation.
Name seven enzymes that are activated during a state of starvation.
Gluconeogenesis enzymes: glucose-6-phosphatase, fructose-2,6-bisphosphatase, pyruvate carboxykinase, phosphoenolpyruvate carboxykinase (PEPCK). FA oxidation enzymes: hormone-sensitive lipase, carnitine acyl transferase. Glycogenolysis enzymes: glycogen phosphorylase. Note that for our purposes, all other enzymes are active during the well-fed state.
Which pancreatic hormone is released by the beta-cells of the pancreas after a meal?
Insulin.
Which pancreatic hormone is released by the alpha-cells of the pancreas during starvation?
Glucagon.
What is the metabolic function of insulin?
It promotes fuel storage and tissue growth after a meal.
What is the metabolic function of glucagon?
It mobilizes fuels during a state of starvation (between meals).
What is the metabolic function of epinephrine?
It mobilizes fuels during acute distress.
Which hormone changes the kind of metabolic fuels recruited for energy over long term starvation?
Cortisol.
What metabolic pathways are positively affected by insulin?
Glycogen storage in liver and muscle, fatty acid storage and synthesis, amino acid uptake and protein synthesis.
What metabolic pathways are positively affected by glucagon?
Gluconeogenesis, glycogenolysis, fatty acid oxidation and release from adipose tissue.
What metabolic pathways are positively affected by epinephrine?
Glycogenolysis, and fatty acid oxidation and release from adipose tissue. Note that epinephrine does not affect gluconeogenesis.
What metabolic pathways are positively affected by cortisol?
Amino acid mobilization and breakdown, gluconeogenesis (from amino acid breakdown), and fatty acid oxidation and release from adipose tissue.
Glucagon and epinephrine bind to a 7-transmembrane receptor and activate a signaling cascade that typically involves which secondary messenger?
cAMP (via activation of adenyl cyclase).
The insulin receptor belongs to which class of receptors?
Tyrosine kinase receptors.
True or False. Akt is involved in the insulin signaling cascade and regulates the translocation of the GLUT4 receptor to plasma membranes.
True.
What are the three domains of steroid hormone receptors?
Hormone binding domain, DNA binding domain, and transcriptional activation domain.
Which protein associated with steroid hormone receptors prevents nuclear translocation when the receptor is not bound to a hormone?
Heat shock protein 90 (hsp90).
What is our primary storage fuel?
Triglycerides (fat).
How long does it take for an individual to deplete liver glycogen stores?
12-18 hours.
Stored triglycerides can provide fuel for up to how many days in a starving individual?
60
What fuels are used to provide energy during the first phase of starvation?
Exogenous fuels. This is the post-prandial well-fed phase.
What fuels are used to provide energy during the post-absorptive state (the second phase of starvation)?
Liver glycogen.
What fuels are used to provide energy during the third phase of starvation?
Amino acids, glycerol and lactate (maintains blood glucose via gluconeogenesis).
During which phase of starvation does the brain begin to adapt to ketone bodies as fuel to provide energy?
Fourth phase.
Which organs keep producing glucose via gluconeogenesis during the fifth state of starvation?
The liver and kidneys.
Which tissues are completely dependent on glucose as a source for energy?
Red blood cells, the brain, the lens of the eye, the medulla of the kidneys and exercising muscle.
True or False. The brain adapts to ketone bodies in individuals with uncontrolled diabetes.
False. The brain does not adapt to ketone bodies to derive energy in diabetics.
What happens to the total amount of nitrogen excreted as urea during starvation?
It increases during early starvation and then decreases during prolonged starvation.
What happens to the amount of nitrogen excreted as ammonia during starvation?
It increases.
Why is it beneficial that nitrogen excreted as ammonia increase during starvation?
It conserves important cations such as sodium and potassium.
The excretion of nitrogen as urea increases during early starvation and then decreases as starvation continues. What is the reason for this trend?
The rate of gluconeogenesis from amino acids decrease during prolonged starvation.
