Flashcards in BIOL 0800 Reading- Chapter 16 Deck (105)
What is the absorptive state?
When ingested nutrients enter the blood from the GI tract
What is the postabsorptive state?
When the GI tract has no more nutrients, and the body's own stores supply energy
What is the different in absorption of carbs/amino acids vs fats?
Fats are absorbed first through the lymph, rather than the blood, in the form of chylomicrons
What is the body's main energy source during the absorptive state?
What is the major consumer of glucose? Why?
Skeletal muscle, because it makes up the majority of the body mass
What mostly happens to glucose in adipocytes?
Turned into triglycerides to be stored as fat: as alpha-glycerol phosphate and fatty acids
What happens to glucose in the liver?
Either turned into glycogen or fatty acids/alpha-glycerol phosphate for storage as triglycerides; triglycerides then packaged into VLDLs for transport to bloodstream
What happens to glucose in the skeletal muscles?
Used up, or turned into glycogen for energy storage for later
What is a VLDL?
Very low density lipoprotein: combination of lipid and protein made in the liver from glucose
What happens to VLDLs in the bloodstream?
Hydrolyzed monoglycerides by lipoprotein lipase for entry into capillaries (otherwise, too big)
Where is lipoprotein lipase located?
On the blood-facing side of the capillary walls, especially in adipose tissue
What happens to the VLDL after the lipoprotein lipase in the capillaries disintegrate it into monoglycerides (glycerol plus fatty acid) and fatty acids?
Fatty acids go into adipocytes to be rebound with alpha-glycerol phosphate to reform into triglycerides; monoglycerides taken up by the liver for metabolism
What happens to absorbed lipids in the blood stream?
Broken down by lipoprotein lipase in adipose-tissue capillaries; fatty acids go into adipocytes for combination with alpha-glycerol phosphate to be stored as triglycerides
Why is glucose critical for lipid absorption?
Because the adipocytes have no other way to get alpha-glycerol phosphate but from breaking down glucose: need it to combine with fatty acids to make triglycerides
What are the three sources of fatty acids in the adipose-tissue triglycerides?
1) glucose enters adipocytes, broken into FAs; 2) glucose enters liver, converted to VLDLs, enters adipocytes, broken into FAs; 3) lipids enter lymph and then adipocytes, broken into FAs
Which cells use/produce cholesterol?
Most cells use it, but cells in the liver and GI tract lining can produce cholesterol to enter the blood
What happens to cholesterol in the liver?
Some secreted into bile to the GI tract; most metabolized into bile salts for secretion into SI
What is the major cholesterol-control organ?
How does ingested cholesterol inhibit liver cholesterol synthesis?
Inhibits the enzyme HMG-CoA reductase: critical for liver cholesterol synthesis
How does cholesterol usually circulate?
As part of different lipoprotein complexes: chylomicrons, VLDLs, HDLs, and LDLs
What are the main cholesterol carriers?
LDLS: deliver cholesterol to the body
How do LDLs bring cholesterol to the body?
Bind to receptors, taken in by endocytosis, release cholesterol to tells
How do HDLs function in terms of cholesterol transport?
Remove cholesterol from blood/tissue; deliver to liver for secretion into bile/conversion to bile salts; ALSO deliver cholesterol to steroid-producing endocrine cells
What kind of lipoprotein complex carries cholesterol to steroid-producing endocrine cells?
What is a major indicator for propensity for atherosclerosis?
Ratio of LDL to HDL: want the number to be low; more HDL than LDL
How does estrogen affect cholesterol levels?
Decreases them because lower LDL and raises HDL
What happens to some amino acids after absorption, by way of the liver?
Used in liver for protein synthesis; OR converted to alpha-keto acids by deamination
What is an alpha-keto acid?
A deaminated amino acid; removed amino groups used to form urea in the liver
What happens to alpha-keto acids after they are synthesized from amino acids?
Enter into Krebs cycle to be catabolized for liver cell energy; can be converted into fatty acids to produce fat in liver