Intermediary Energetics & Metabolism Flashcards
What are the pathways of energy metabolism?
lipids are in general metabolized by Beta-oxidation
What is the role of glucose in energy metabolism?
Glucose has a central role
Blood glucose levels must be tightly regulated (by insulin & glucagon)
- important source of energy
- brain tissues cannot synthesize glucose so are dependent on blood glucose
What does insulin being anabolic mean?
it enables an animal to put on weight by increasing glucose and amino acid uptake by cells.
it stimulates the synthesis of:
- glycogen in the liver & muscles
- protein in muscle tissue
- triacylglycerols in adipose tissue
What happens after a meal vs after a short fast?
- immediately after a meal there will be an excess of carbs that will be broken down into their monomer sugars, which will be used for energy or stored as glycogen (if there is a big excess, it may be converted to lipid)
- if there is a short fast for a few hours, glucose from the meal has already been disposed of & used (then there may be a need to do gluconeogenesis to help maintain blood glucose levels)
How are lipids used as an energy source?
- lipids are broken down into free FAs until they can be used
- Acetyl CoA can be used to make a lot of ATP (OR in times of a slightly longer fast (run out of carb substrate to make glucose), then might go into the production of ketone bodies for use in the brain)
What happens during a medium fast?
- After the carbohydrate pool has been depleted, then lipids will come in to produce Acetyl CoA to make ketones
- but the glycerol backbone & odd-chain FAs cannot actually be made into Acetyl CoA (need to be made into pyruvate)
- gluconeogenesis can still occur & the protein pool can be used to make glucose too (but this tends to come later as the body wants to conserve your proteins)
What do AA do in the Kreb’s cycle?
- some AA are glucogenic only, some are ketogenic only, & some do both
- some have multiple steps
- some can make an intermediate in the TCA cycle or some can make pyruvate
What happens during prolonged starvation?
- carbs & fats are depleted
- start relying on the protein pool
- may even start to break down your skeletal muscle & cells
- you can maintain blood glucose (energy for the brain) via ketones until the protein pool runs out
What is the source of glucose, the consuming tissues, and the greatest brain nutrient in the post-prandial phase?
exogenous glucose source, all tissues are consuming, greatest brain nutrient = glucose
What is the source of glucose, the consuming tissues, and the greatest brain nutrient in the short to medium fast phase (ex: an overnight fast)?
Source is glycogen & gluconeogenesis, consuming tissues are all but muscle & liver, and the greatest brain nutrient is glucose
What is the source of glucose, the consuming tissues, and the greatest brain nutrient in the long fast phase (ex: a day or more w/o eating)?
glucose comes from gluconeogenesis, the consuming tissue is the brain, and the greatest brain nutrient is glucose
What is the source of glucose, the consuming tissues, and the greatest brain nutrient in the starvation phase?
there is no source of glucose so use ketone bodies instead, consuming tissue is the brain, and the greatest brain nutrient is ketone bodies
How does insulin respond to high & low glycemic index foods?
What happens with consumption of a high glycemic load meal?
-> high serum glucose and insulin -> rapid uptake of serum glucose and AAs -> high fat & protein deposition
What happens with consumption of a low glycemic load meal?
low serum glucose & insulin -> slow uptake of serum glucose & AAs -> low fat & protein deposition
What kind of diets have carnivores evolved for?
high protein, low carbohydrate
How have carnivores evolved for high protein, low carbohydrate diets?
- have high rates of gluconeogenesis, even after a meal
- some AAs, particularly arginine, can stimulate insulin release
How can carnivores appear ‘glucose intolerant’ if fed a high carbohydrate diet?
- postprandial hyperglycemia due to continued gluconeogenesis AND glucose surge w/ a meal
- tend to have v prolonged postprandial hyperglycemia
Why do we feed cats so much carbs?
b/c protein is expensive
Does glycemic index impact protein deposition in pigs?
low glycemic starch sources reduce protein deposition in pigs
How can eating things as a meal affect glycemic index?
Because fat and fiber can slow gastric emptying so only small amounts of the digestive stuff are getting into the intestine for absorption at time
