Nutrition Metabolism Review Flashcards
What is the main function of the GI system?
Extracts chemical energy from food and makes it available for work in different tissue so fate body, and at different times throughout the day.
How is glucose stored?
- Glycogen
- TAG
How are fats stored?
-TAG
How are amino acids stored?
They aren’t usually stored unless turned into muscle –> protein synthesis
What are the four important metabolic states (normal physiological states)?
- Fed
- Fasted
- Starved
- Hypercatabolic
What is the fed state?
Lasts 2-4 hours after a meal
What is the fasted state?
Overnight without eating
What is the starved state?
Prolonged fasting
What is the Hypercatabolic state?
Trauma, sepsis, etc.: not related to meals
What is the teleological statement about organ responses to feeding (what the body wants)?
After eating, body wants to store calories that exceed its immediate energy needs, so that it can withstand periods of nutrient unavailability. The body stores excess calories as carbohydrate, fat and protein.
What is the mechanistic statement about organ responses to feeding (how it happens)?
After eating, nutrients stimulate the release of specific hormones, such as insulin, that upregulate biosynthetic pathways in different tissues
What is the most important hormone regulating storage pathways in the fed state?
Insulin
What cell release insulin?
Pancreatic beta cells
What is insulin release from pancreatic beta cells directly responsive to?
The concentration of glucose in the blood.
What is the function of insulin?
Insulin inhibits the release of glucagon, the major regulator of catabolism in the fasted state.
What determines the ratio of insulin to glucagon?
Relative amount of carbohydrates in the meal
What do high carbs or high protein in a meal determine?
High carbs –> more insulin
High protein –> less insulin, more glucagon
What is the primary organ responsible for maintaining glucose homeostasis?
Liver
After eating a carbohydrate rich meal, what two things happen?
- biosynthetic pathways that produce glucose (glycogenolysis, gluconeogenesis) are inhibited.
- Metabolic pathways that store glucose (fatty acid biosynthesis, cholesterol biosynthesis, protein synthesis, glycogenogenesis) are activated.
After eating a protein rich meal, what happens?
Elevated amino acids in the blood increase the secretion of glucagon by pancreatic alpha cells.
What are excess amino acids used for by the liver (when you have elevated amino acids in blood)?
Used in liver for gluconeogenesis.
How does the brain respond to feeding?
Oxidizes glucose to CO2 to make ATP through oxidative phosphorylation.
How do RBCs respond to feeding?
Ferments glucose to pyruvate; exports lactate
How do white adipose cells respond to feeding?
Ferments glucose to glycerol 3-phosphate, the backbone for triacylglycerol synthesis.
How does skeletal muscle respond to feeding?
Glycolysis, fatty acid beta oxidation, glycogenogenesis, protein synthesis
How does cardiac muscle respond to feeding?
Fatty acid beta oxidation (60-80%); Oxidation of glucose and lactate (20-40%).
How do Intestinal epithelial cells respond to feeding?
Convert glutamine, glutamate and aspartate from the diet to alpha-ketoglutarate.
How do Colonocytes respond to feeding?
Use short chain fatty acids produced by gut bacteria.
What is the main function of the liver in feeding?
Liver increases production and export of glucose for use by other tissues.
What does glycogenolysis use?
Hepatic glycogen stores
What does gluconeogenesis use?
Carbon skeletons from amino acids, lactate, and glycerol to produce glucose.
Where does the ATP powering gluconeogenesis come from?
FAD(2H) and NADH reduced by fatty acid beta oxidation
What is the acetyl CoA produced by fatty acid beta oxidation used for?
It’s a substrate for ketone body synthesis.
What do gut epithelial cells use as their primary fuel in the fasted state?
They still use glutamine as their primary fuel in the fasted state, but it comes from the blood, not the lumen of the gut.
What will RBC always ferment, no matter the metabolic state?
RBC will always ferment glucose to lactate.
