3.7 Gastrointestinal Physiology Metabolism Flashcards
metabolism means?
change
*refers to all the chemical and energy transformations that occur as the body is dealing with nutrients (carbs, fats, and protein) that have been absorbed
what are the two functional statres or periods of metabolism?
1) absorptive
2) postabsortive
define absorptive metabolism
right away
*ingested nutrients are entering the blood from the GI tract, utilized, and excess stored
define postabsorptive metabolism
hours after
*nutrients are taken from storage for use when the GI tract is empty
when are we in postabsorptive state of metabolism?
absorption of average meal is 4 hours after
* only during late morning, late afternoon, and during the night
the conversion of fructose to galactose is to maintain? happens where?
- maintains circulating glucose
- conversion in mucosal cells
- galactose to glucose happens in liver
cellular uptake of glucose is via? what parts of body do this?
1) via Na+ dependent secondary active transport (intestinal mucosa, kidney tubule cells, nerve/brain cells, liver)
2) via insulin dependent facilitated diffusion (most cells in body)
insulin dependent facilitated diffusion of glucose work?
1) insulin binds to receptors on cell membranes
2) promote that making of proteins that travel through cytoplasm
3) become transport protein in plasma membrane
4) helps transport glucose INSIDE via facilitated diffusion
what is insulin? Promotes what?
PROTEIN HORMONE
- hormone of excess= promotes storage
- promote glycogenesis
excess glucose is stored as? where?
- glycogen (liver and muscles)
- fat (adipocytes and liver)
- **stored as fat only after glycogen stores are saturated
normal intracellular glucose is low or high? Why?
low
*immediately used or converted to glycogenor fat
insulin > increase _____ > storage
glycogenesis
glucagon > increases _____ > mobilization
glycogenolysis
what does lipoprotein lipase do?
an enzyme on endothelial cells lining capillaries that promotes glucose intake by muscles, adipocytes, and liver
glycogenolysis in muscles
glycogen > glucose 6P = energy
- NONE released into blood
- phosphate group presens
glycogenolysis in liver
glycogen > glucose 6P = energy OR RELEASED into blood
*Glucose 6-Phosphatase
glycogenolysis in hormones
epinephrine and glucagon both increase glycogenolysis
- epi in muscle
- glucagon in liver
how do we get glucose from none CHO sources?
gluconeogenesis primarily in liver
*Ex: fat and protein
hormones in gluconeogenesis?
glucagon and glucocorticoids both increase gluconeogenesis
what is glucagons main role?
raise blood glucose levels
what is the “sparing effect”
Use CHO as first choice energy source to spare fat and protein usage
anaerobic glycolysis? produces
can utilize CHO anaerobically and produces lactic acid
removal of chylomicrons happens in what state? How?
absorptive state
* by adipose tissue for stoaage and by the liver for storage and synthesis of phospholipids
removal of chylomicrons from blood by adipose tissue?
lipoprotein lipase (an enzyme onendothelial cell surface of capillaries within adipose tissue) *taken up by adipose cell; hydrolyzed TG of chylomicrons into FA +glycerol and resynthesized to TG
removal of chylomicrons from blood via liver?
chylomircon remnants taken up ans released as something else bc they are rich in cholesterol and make VLDL
what activated lipoprotein lipase?
insulin
when glycogen stores are depleted, what is mobilized for energy? unique how?
fat
*unique bc it has the MOST energy stored
ketones used when? How?
1) low CHO
2) diabetic state
* taken up by cellsm converted to acetyl CoA, and then oxidized for energy (Krebs)
ketones made by?
fatty acids
protein metabolism: AA taken up how? stored?
taken up by secondary active transport couples to Na+ and immediatly made into protein and stored
growth hormone, insulin, estrogen, and testosterone all stimulate?
cellular uptake and storage (as proteins) of amino acids
plasma proteins are synthesized in liver except for?
- gamma globulin that are synthesized in lymphoid tissue
* *liver= albumin and alpha/beta
what hormone catabolizes steroids?
glucocorticoids
gluconeogenesis is converstion of aa to?
glucose (alanine and others)
ketogenesis is conversion of aa to?
fat (leucine, isoleucine, phenylalanine, tyrosine)
what is the most prevalent glucocorticoid in humans?
cortisol
