Biochemistry of Nutrition

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Biochemistry of Nutrition
2012-02-03 21:47:35
Block Murakami

Biochem of Nutrition
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  1. What is the difference between a macronutrient and a micronutrient?
    Need grams of macronutrient per day and mg or less of micronutrients per day.
  2. Name the 7 macronutrients
    Protein, carbohydrates, fat, cholesterol, sodium, potassium, fiber
  3. What is the daily reference value for the following:
    Saturated fat
    Total carbohydrates
    • Fat: 65 g
    • Saturated fat: 20g
    • Cholesterol: no more than 300 mg
    • Total carbohydrates: 300 g
    • Fiber: 25 g
    • Protein: 50 g
    • Sodium: 2.4 g
    • Potassium: 3.5 g
  4. What are the three major energy expenditures?
    • Basal metabolic rate: (1800 for 70 kg male, 1300 for 50 kg woman)
    • Physical activity
    • Thermic effect
  5. What is the relationship of total corie expenditre to BMR?
    150% BMR
  6. What is the amount of energy (in kcal/g) in the following:
    Fatty acids
    • Carbohydrates: 4kcal/g
    • Fatty acids: 9kcal/g
    • Protein: 4kcal/g
  7. What percentage should each of the following make up as a person's total calorie intake (what are the acceptable macronutrient distribution ranges- AMRDs):
    • Carbs: 45-65%
    • Fat: 20-35%
    • Protein: 35%
  8. What are the four standards for DRI (dietary reference intake)?
    • Estimated average requirement (EAR): the intake at which the risk of inadequacy is 50%
    • Recommended dietary/daily allowances (RDA): the intake at which the risk of inadequacy is 2-3%
    • Adequate intake (AI): based on an estimate of nutrient intake in healthy people
    • Tolerable upper intake level (UL): at an intake above this level the risk of adverse effects increases
  9. What is the reference daily intkae for the following micronutrients?
    Vitamin B12
    • Calcium: 1.0 g
    • Vitamin B12: 6 ug
    • Phosphorus: 1.0 g
    • Iodine: 150 ug
  10. Salivary amylase: what does it do?
    • Digestion of carbs
    • Hydrolyzes alpha-1,4 link
  11. Pancreatic amylase: what does it do? Where does it live?
    • Digestion of carbs
    • Highest in duodenal lumen
    • Hydrolyzes to disacchardies/oligosaccharides
  12. Oligosaccharide hydrolases: where does it live, what does it do?
    What other enzymes reside in the intestinal cells?
    • Digestion of carbs
    • Lives in brush border of intestines
    • Makes monosaccharides

    • Enzymes of intestinal cells include:
    • Maltase and Isomaltase (Maltose, Isomaltose to Glucose)
    • Sucrase (Lactose to Glucose + Galactose)
    • Lactase (Lactose to Glucose + Galactose)
  13. Glucose and galactose
    • Digestion of carbs
    • Uses GLUT 1-4 and SGLT1
  14. List the functions of transporters GLUT1-5 and SGLT1
    • GLUT1 (abundant in blood cells/low in adult muscle)
    • GLUT2 (abundant in liver and kidney)
    • GLUT3 (primarily neurons)
    • GLUT4 (insulin dependent; abundant in adipose and skeletal muscle)
    • GLUT5 (fructose transporter)
    • SGLT1 (sodium dependent glucose transporter1) requires energy (ATP).
  15. Describe the digestion of triglycerides
    Pancreatic lipase/colipase: TG--> MG--> Membrane --> Nascent chylomicron (apoB48; Need C-II and E from HDL for mature form)
  16. What are the hormones that control lipid digestion?
    • Cholecystokinin (CCK0)
    • Secretin
  17. What happens in the following (think malabsorption):
    Enzyme deficiency:
    Pancreatic insufficiency:
    • Enzyme deficiency: reduced absorption of fatty acids and fat-soluble vitamins
    • Abeta-lipoproteinemia (apoB deficiency; fat accumulation in enterocytes)
    • Pancreatic insufficiency (fat and fat-soluble vitaminsmalabsorption)
  18. Describe the following malabsorbtion disorders:
    Tropical sprue:
    Whipple’s disease:
    Celiac sprue:
    Disaccharidase deficiency:
    Pancreatic insufficiency:
    • Tropical sprue: Probably infectious. Similar to celiac sprue but can affect entire small bowel
    • Whipple’s disease: Infection with gram positive, Tropheryma whippeli
    • Celiac sprue: Reaction/atutoantibodies to gluten (wheat and other grains)
    • Disaccharidase deficiency: Most common is Lactase deficiency (commonly seen in Native Americans and Asian Americans)
    • Abetalipoproteinemia: apoB deficiency
    • Pancreatic insufficiency: Some causes include cystic fibrosis, obstructing cancer, chronic pancreatitis
  19. List 3 pancreatic excretions responsible for TG digestion
    Lipase, phospholipase A, colipase
  20. List one pancreatic secretion responsible for carbohydrate digestion
  21. Can amino acids be stored?
  22. Describe the pathway for protein degradation in the GI
    Protein enters the stomach where it is broken down by HCl and pepsin and broken down into peptides. These peptides enter the small intestines where it is greeted by the following secretions from the pancreas: HCO3-, tripsinogen, chymotrypsinogen, proelastase, procarboxypeptidases A and B. These secretions turn the peptides into aminopeptidases, di-peptides and tri-peptides and amino acids. All of these are absorbed by the intestinal epithelial cells, broken down into amino acids and released into the blood stream.
  23. What is achlorhydria?
    HCl deficiency in the stomach- causes deficiency in protein digestion and absorbtion
  24. What are zymogens?
    They are the proenzymes that hang around to be converted into active enzymes. Most of them end with -ogen or being with Pro- (pepsinogen --> pepsin; proelastase --> elastase)
  25. How is bicarbonate secretion sitmulated and what happens when there is a deficiency?
    Secreted in response to secretin, deficiency leads to peptic ulcer (mucosal erosions)
  26. Tell me about enteropeptidase and trypsin
    They are enzymes for protein digestion that act through 2-step activation: enteropeptidase activates trypsin which activates other protein digesting enzymes
  27. Describe transport of amino acid from the intestinal lumen to the blood
    • Two paths:
    • 1. Using transporters: sodium-amino acid carrier system into the intestinal cells (Na+ dependent co-transporter)
    • 2. Into the blood or out of the cells:
    • - amino acid: concentration gradient/facilitated transporter
    • - Sodium ion Na+ - K+ ATPase
  28. What is cystinuria?
    • A disorder of the proximal tubule's reabsorbtion of filtered cystine and dibasic amino acids: lysine, ornithine, arginine. Leads to accumulation and precipitation of cystine stones in the urinary tract.
    • Causes amino acid malabsorbtion in the intestines and resporbtion in the kidney
  29. What is Hartnup disease?
    • Defect in the transport of neutral amino acids
    • Causes intestinal AA malabsorbtion and decreased renal AA reabsorbtion
  30. How are amino acids transported into the intestinal lumen?
    Using y-glutamyl cycle (by GGT; y-glutamyl transferase). Amino acids react with glutathione on the lumen membrane and forms y-glutamyl amino acid and is then released into the cytoplasm
  31. What does high serum GGT indicate?
    Liver disease
  32. List some major stimulants of proteasome activities
    • In musle: glucocorticoids
    • Uncontrolled diabetes: bc insulin cannot suppress glucocorticoid activity
    • Sespis, cancer and burn injuries: TNF and interlukins stimulate proteasome activity in muscle
  33. What are the two major pathways for protein degradation in the cells?
    • Ubiquitin-proteasome pathway: mainly endogenous proteins
    • Lysosomal protein tunover: mainly extracellular proteins; endocytosis
  34. Tell me some things about the ubiquitin-proteasome pathway
    • 26S protease complex called the proteasome- important for breaking protein down into peptides.
    • The pathway has 3 active forms: 20S proteasome, PA700 Cap protein (19S), and 26S proteosome which requires ATP for proteolysis