Digestion and Excretion

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Digestion and Excretion
2012-07-17 10:01:43

MCAT Biology
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  1. Order of anatomy of the digestive tract?
    Mouth --> Esophagus --> Stomach --> Small intestine --> Larhe intestine --> Rectum --> Anus 
  2. Where does digestion begin? What marcomolecule first begins digestion and with what enzyme?
    Digestion begins in the mouth ; Digestion of startch (carb) with alpha-amylase 
  3. What is the bolus transformed into in the stomach?
  4. What kind of glands does the stomach contain?
    Exocrine glands - known because they release enzymes 
  5. Where does protein digestion start and with what enzyme?
    In the stomach with pepsin 
  6. 4 cells in stomach and their actions
    1. Mucous cells - lubrication+protection from pH

    2. Chief cells - secrete pepsinogen 

    3. Parietal cells - secrete HCl 

    4. G cells  - secrete gastrin (stimulate parietal cells to secrete HCl) 
  7. Where does absorption occur?
    Small intestine 
  8. Parts of the small intestine and what occurs where
    1. Duodenum - most digestion 

    2. Jejunum - absorption 

    3. Ileum  - absorption 
  9. Surface of small intestinal wall
    Brush border (contains enzymes to break down carbs, proteins, and nucleotides)--> microvilli --> Villi (increase surface area for absorption) --> lacteal capillary network (site of nutrient absorption) -->

    Exocrine glands within villi = secrete 7.6 intestinal juice 
  10. Goblet cells 
    • Found in the small intestine, secrete mucus for protection 
  11. What is the pH in the small intestine and why does it have its value?
    pH of 6 

    Slightly basic compared to stomach because of bicarbonate ion  
  12. What does the pancreas secrete through its exocrine abilities?
    1. Bicarbonate ion to alter pH of duodenum 

    2. Trypsin, Chymotrypsin, Pancreatic amylase, Lipase, RiboandDeoxyribonuclease  
  13. All enzymes released from pancreas are released as...
    Zymogens! Activated by trypsin 
  14. How are carbohydrates absorbed?
    Broken down into di and trisaccharides by pancreatic amylase 

    Further broken to monosaccharides by brush border enzymes

    Absorbed as monosaccharides  
  15. Where is bile produced and stored? What are its functions?
    Produced by the liver and stored in the gall bladder

    Bile emulsifies fat in the small intestine, increasing its surface area and making it easier to be absorbed by enterocytes

    Bile does NOT digest fat at all  
  16. What is bilirubin?
    Endproduct of Hb degradation
  17. What are the major functions of the large intestine?
    • 1. Water absorption 
    • 2. Electrolyte absorption  
    • 3. Symbiotic hub for gut flora like E.Coli (produce Vitamins)  
  18. What composes healthy poop?
    • 1. Water 
    • 2. Dead bacteria
    • 3. Fat
    • 4. Inorganic matter
    • 5. Protein
    • 6. Roughage
  19. What do the hormones secreted by the small intestine do?
    Increase blood insulin levels , peptide hormones
  20. Carbohydrate absorption
    • 1. Broken down into monomers glucose, fructose, galactose 
    • 2. Absorbed via secondary active transport glucose absorbed into enterocyte with Na+) 
    • 3.  Glucose move out of cell via facilitated transport from intestinal lumen --> enterocyte ... but passive/facilitated diffusion from enterocyte --> blood
    • 4.  Carried to liver 
    • 5. If max [glycogen] reached by cells, converted to fatty acids
  21. Where does the conversion of glucose to fat take place?
    Liver + fat cells
  22. Protein absorption 
    • 1. Absorbed into enterocytes via active or facilitated transport 
    • 2. Cells immediately make protein from amino acids to keep amino acid [] low 
  23. What is ammonia converted to and by what?
    Converted to urea by the liver and then excreted by the kidney 
  24. Energy in protein, carbs, and fat 
    Fat > Carbs > Protein 
  25. Fat absorption
    • 1. Separated by bile micells and broken down by lipase and brush border enzymes 
    • 2. Once in cell, fats re-converted into triglycerides at sER 
    • 3. Attached to apoproteins = chylomicrons 
    • 4. Exocytosed by cells
    • 5. Move into lacteal of lymph system
    • 6. Enter thoracic duct  
    • 7. Jugular Vein 
    • 8. Absorbed into liver and other cells
  26. Blood supply to liver
    • 1. Nutrients: hepatic portal vein 
    • 2. Oxygen: hepatic artery  
  27. 8 jobs of the liver?
    • 1. Blood reservoir 
    • 2. Blood filtration
    • 3. Carbohydrate metabolism
    • 4. Fat metabolism
    • 5. Protein metabolism
    • 6. Detoxification (lots of sER)
    • 7. RBC destruction (but mostly by spleen)
    • 8. Vitamin storage
  28. Albumin 
    osmoregulatory factor, binds to lipids to transport through blood 
  29. How does oxidation of protein and fat by the liver affect blood pH?
    pH will DECREASE, acidity increases 

    keto acidosis  
  30. Functions of the kidney
    • 1. Excretion of waste 
    • 2. Homeostasis
    • 3. pH control
  31. Path of excretion
    Urine created by kidnet and emptied into --> renal pelvis --> ureter --> bladder --> urethra

    glomerulus --> Bowman's capsule --> PCT --> Loop of henle --> DCT --> collecting duct --> ureter  
  32. What is the functional unit of the kidney?
  33. What force allows glomerular filtration to occur?
    Hydrostatic pressure
  34. What molecules are PREVENTED from filtering into the bowman's capsule through the glomerulus?
    Blood cells and large proteins
  35. Where does most reabsorption in the kidney take place?
    Proximal tubule 

    • 1. glucose, amino acids, vitamins, and water is reabsorbed
    • 2. Toxins, uric acid, drugs, and H+ ions are secreted  
  36. What is the job of the Loop of Henle?
    To concentrate the renal medulla! This will allow for H2O absoroption later on...

    Filtrate entering loop is more concentrated than filtrate exiting loop.

    • Descending: water absorbed 
    • Ascending: Na+ absorbed  
  37. What is the job of the distal tubule?
    Lower filtrate osmolarity 

    Reabsorption of Na+ and Ca2+ 

    Secretion of K+, H+, and HCO3-
  38. Where does aldosterone exert its effects?
    Distal tubule 
  39. What is the job of the collecting duct?
    To concentrate urine 
  40. Where does ADH exert its effects?
    The collecting duct to increase permeability to water and concentrating the filtrate 
  41. Water permeability in the loop of henle
    Descending branch - permeable to water 

    Ascending - Impermeable to water  
  42. RAA system
    Renin secreted by kidney - acts as a catalyst because it's an enzyme

    Adrenal cortex stimulated to secrete aldosterone
  43. Where does most mechanical and chemical digestion occur?
    Mechanical: mouth 

    Chemical: Duodenum  
  44. How do most fats enter circulation?
    First converted to chylomicrons and shipped to lacteal lymph system to be deposted in thoracic duct
  45. Main effect on BP of the RAA?
    Increase in systemic blood pressure
  46. By what organ is the pH of the small intestine maintained? 
    The pancreas releases bicarbonate ions into the small intestine to maintain the pH 
  47. Most of the main
    stomach cells have extensive rough ER except for the parietal cells, which have
    tons of mitochondria to help make the energy to maintain the high proton []
  48. How and where does glucose enter cells via SECONDARY active transport?
    Where: Enterocytes & Proximal convoluted tubule

    How: Secondary active transport is indirectly harnessing ATP energy to move molecules.

    Na+ transporter/ATPase pumps Na+ out of cell against its [] gradient. A Glucose/Na+ coupler transporter take both glucose and Na+ into cell down Na+s gradient - the second step does not require ATP since it's facilitated 
  49. When insulin is present, how does glucose enter most cells?
    Facilitated diffusion except for in neurons
  50. Examples in primary active transport
    The transportation of species with the direct harnessing of ATP energy 

    Ca2+ pump in muscles, Na+/K+ pump, proton pump in gastric cells