Energy Sources & Their Metabolism Flashcards
Major dietary carbohydrates
Starch, cellulose, sucrose, lactose
Starch
Glucose polymer (alpha 1,4 linkages)
Cellulose
Glucose polymer (beta 1,4 linkages)
Sucrose
Glucose and fructose disaccharide
Lactose
Galactose and glucose disaccharide
Starch or Cellulose?
Humans do not have the enzyme to recognize the beta linkages in cellulose, so we cannot process it. However, alpha-amylase recognizes alpha linkages in starch so we can process it
Carbohydrate digestion
Enzymes: alpha-amylase, hydrolases
Where: small intestine
Other organs: mouth, stomach, pancreas
Lipid digestion
Enzymes: lipase, bile acids
Where: small intestine
Other organs: gallbladder, liver, pancreas, stomach
Protein digestion
Enzymes: peptidases, pepsin, HCl
Where: small intestine
Other organs: stomach, pancreas
Carbohydrate absorption
Broken up into glucose, galactose, fructose, and absorbed through villi of small intestine, GLUT transporters get them into the blood stream to be taken to other tissue
Lipid absorption
Broken up into monoacylglycerol and fatty acids, taken up by transporters on intestinal epithelial cells through facilitated diffusion, fatty acid and monoacylglycerol are recombined into a triglyceride and loaded on apoB48. This makes chylomicron, making the fats soluble in blood, where cells will have the means of extracting fatty acids from chylomicrons. The remnants go to the liver and turn into VLDL, cycles in the blood, then remnants of that go back to the liver (chylomicrons are made of fatty acids and cholesterol). LDL into extrahepatic tissue if it is needed, otherwise it goes to the liver.
Protein absorption
Broken down into amino acids, where specific substrates bind amino acid on intestinal lumen to create an Na+ gradient, which pulls in the amino acid through secondary diffusion. From there, it can use facilitated diffusion to get into the bloodstream
How do tissues get dietary fuel?
From either the upper or lower GI tract, nutrients go through the splenic vein or superior mesenteric vein (respectively) and into the hepatic portal vein. This takes them to the liver, where they go into the hepatic veins, to the inferior vena cava, which takes it to the heart. The heart pumps the nutrients out into the abdominal aorta and into the proper hepatic artery, where it ends up back at the liver.
Enzyme
Lowers the activation energy of a reaction
Why don’t we want equilibrium?
Because being at equilibrium means we are dead, our bodies work to maintain homeostasis instead
