3.2-Fed/Fast Cycle Flashcards
Big picture Q: What are the major suppliers for GNG? ALSO where do these come from?
Lactate! (Major one, from Muscle) AAs (Alanine from Muscle, Glutamate from diet, and Glutamine from diet), Glycerol (from Adipose)
About how many g of glucose does the brain consume per day? What percentage of total body glucose is this?
120g/day…60% of body’s glucose
Why doesn’t the CNS use fat for fuel?
It cannot cross the blood/brain barrier
What are the three major fuels for muscle?
glucose, fatty acids, ketone bodies
What is the main fuel for muscle during exertion? What about rest?
Glucose (glycolysis not CAC and beyond) during exertion and rest it uses FA’s
What is the heart’s main fuel? What are its two alternatives?
Fatty Acids, with ketone bodies and lactate as alternatives
Why is the amount of glucose in an adipose cell a major factor in determining whether FAs are released to the blood?
HAS TO DO WITH G-3-P: Low glucose=low G-3-P=get FAs out, High glucose = high G-3-P, time to store
What is the task of the kidney that requires a lot of energy?
Reabsorption of nutrients from blood
What main metabolic task does the kidney perform under starvation circumstances?
GNG, can be 1/2 of all blood glucose!!
About how much glucose is removed from blood by the liver?
About 2/3!!
What three things does the liver synthesize when there is an abundance of glucose around? ALSO what metabolic pathway does it perform to get NADPH?
Fatty Acids, Cholesterol, and Bile Salts….PPPathway!
What molecule prevents long chain FAs from entering the matrix?
Malonyl CoA. (wants to MAKE fat not break it down!)
What are FAs converted to in a starvation state?
Ketone Bodies! Remember, we can not make Glucose from acetyl-CoA!!
What is the primary use of dietary AAs that go to the liveR?
Protein Synthesis! Not necessarily catabolism
Which AAs have to be catabolised in the muscle because the liver cannot do it?
Leucine, IsoLeucine, Valine.. Because they are all branched!
Which product of ketone body formation cannot be used by the liver? (What a nice organ, it sends it to the brain :)
Ace-to-ace-tate
What 2 processes does the liver perform when entering our early fasting state?
Get glucose into the blood! Glycogenolysis and GNG!
What is the phenomena happening after 2 days of starvation and GNG starts to drop in production?
Ketone bodies are now being produced and the brain can run off those
What is the key pathway as we begin to go into prolonged starvation?
GNG
What is the very friendly thing that muscle does to help the body out in prolonged starvation?
Muscle initially loves using Ketone bodies, but going into prolonged starvation, muscle stops using them and gives them to the brain. This puts less strain on the liver to stop having to to GNG! (sparing the protein precursors)
During prolonged fasting: does the utilization of ketone bodies increase or decrease?
Decrease
During prolonged fasting: does utilization of ketone bodies in the brain increase or decrease?
Increase
During prolonged fasting: does the liver increase or decrease GNG?
Decrease (its expensive!)
During prolonged fasting: does muscle increase or decrease protein degradation?
Decrease (hold on to what you can!)
