Biochem Flashcards
(93 cards)
1
Q
What is Hartnup disease?
A
congenital defect in the mechanism that transports neutral aa in intestine
2
Q
- What is cystinuria?
A
congenital defect in the transport of cysteine (basic aa)
3
Q
- What is a potential reason for protein food allergy?
A
- if foreign proteins enter the blood without first being broken down to aa, it can provoke the formation of antibodies
4
Q
- What enzymes are in the brush border? What is their product?
A
- endopeptidase, aminopeptidase, and dipeptidase; product is free aa or di and tri peptides
5
Q
- Where is pepsin and what is it activated by? What is the product?
A
- in the stomach, activated by H+ or pepsin; products are peptides
6
Q
- Where is trypsin located and what is it activated by?
A
- in the small intestine, activated by enteropeptidase or trypsin
7
Q
- What other enzymes are found in the small intestine? What activates these enzymes?
A
- chymotrypsin, elastase, carboxypeptidase A, carboxypeptidase B; activated by trypsin
8
Q
- Where does protein digestion start and why? Where is most protein absorbed?
A
- starts in stomach due to acidic condition and pepsin; absorption in small intestine
9
Q
- What is the process of protein digestion within the stomach?
A
- parietal cells secrete HCl, K+ and H+ exchanging ATPase, K+ and Cl- channels, Cl- and HCO3- exchange
10
Q
- What kind of cells secrete pepsinogen and when? What does this eventually form?
A
- chief cells secrete pepsinogen, autoactivated at pH <5, forming pepsin
11
Q
- What stimulates the secretion of pepsinogen and acid?
A
- histamine and gastrin
12
Q
- What are the three functions of HCl?
A
- denature proteins, kills bacteria, and activates pepsinogen
13
Q
- Products from the stomach stimulate secretion of what in the duodenum?
A
- cholecystokinin and secretin (hormones that will stimulate pancreatic digestive pro-enzymes and enteropeptidases from modified mucosal cells
14
Q
- What are four pancreatic pro enzymes and what activates them?
A
- proelastase, procarboxypeptidase, chymptrypsin, and trypsinogen; activated by trypsin
15
Q
- What aa do the following pancreatic proteases cleave what aa bonds?
a) trypsin
b) chymotrypsin
c) elastase
d) carboxypeptidase A
e) carboxypeptidase B
A
- a) basic aa – Arg, Lys
b) aromatic (Phe, Trp, Tyr), Met, Leu
c) neutral aa – Ala, Gly, Ser
d) Ala, Ile, Leu, Val
e) Arg, Lys
16
Q
- AA have specific transport systems that are normally dependent on what?
A
- Na+ or H+ dependent, and ATP used in active processes
17
Q
- What are the essential aa?
A
- F, V, T, W, I, M, H, L, K, and R for growing kids
18
Q
- What are the majority of lipids in the diet consumed?
A
90% TAGs
19
Q
- What are the four locations and their major component of lipid digestion?
A
- mouth – lingual lipase (minimal), stomach – lingual and gastric lipase, SI – pancreatic enzymes and bile salts, jejunum – absorption
20
Q
- What do all lipases do?
A
- FA removed from positions 1 and 3; leaves 2 FFA and 2-MAG
21
Q
- Where is lingual lipase secreted? What is optimum pH? Is it slow or fast activity?
A
- secreted by cells at back of tongue, acid, slower activity bc only active at surface of lipid droplet
22
Q
- Where is gastric lipase secreted? What is optimum pH? Is it slow or fast activity?
A
- secreted by gastric mucosa, acid, limited to surface of lipid droplet – but speed increased by peristaltic movement
23
Q
- What do pancreatic lipases require? How is this made? Why is this necessary?
A
- colipase; trypsin converts procolipase to colipase; lipase alone is inhibited by bile salts, so, colipase binds lipase to mixed micelles preventing inhibition of lipase by bile salts
24
Q
- How much of TAG are hydrolyzed all the way to glycerol and FFA?
A
- 20%
25
8. Phospholipase A2 – secreted as what? Activated by what? Requires what?
8. secreted as zymogen (prophospholipase A2), activated by trypsin, requires bile salts
26
9. What does phospholipase A2 do and what is its product?
9. removes one FA molecule from 2 position of phospholipids to yield one FFA and one lysophospholipid
27
10. What is cholesterol esterase?
10. an esterase that will accept MAG or cholesteryl esters as substrates to hydrolyze to cholesterol and FFA
28
11. What is bile derived from? Where is it made? Where is it stored?
11. derived from cholesterol, made in liver, stored in gallbladder
29
12. What is in bile? What do these things form?
12. bile salts, phospholipids (PC), cholesterol; form micelles
30
13. What constitutes a mixed micelle? What does this aid?
13. once digestion starts, products of digestion are added (such as fat soluble vitamins); aids distribution of products to the intestinal epithelium for absorption
31
14. Most lipids are absorbed by what process?
14. simple diffusion
32
15. What are the three carriers for cholesterol?
15. NPC1L1 (major), SCARB1, CD36
33
16. Virtually all ________________ are absorbed but only 30-40% of ________ is absorbed.
16. FFA and MAG, dietary cholesterol
34
17. Absorbed lipids are repackaged into what by intestinal epithelial cells?
chylomicrons
35
18. What is it called when bile salts are absorbed and then returned to the liver?
18. enterohepatic circulation
36
19. What enzyme converts FFAs to fatty acyl-CoAs?
19. fatty acyl-CoA synthase
37
20. Ultimately, absorbed lipids are turned back into _______ by what pathway?
20. TAGs by monoacylglycerol pathway
38
21. What is an alternative pathway to synthesize TAGs?
21. phosphatidic acid pathway
39
22. How are SCFA and MCFA transported to the liver?
22. enter hepatic portal vein as FFA, to liver bound to albumin
40
23. What is the major apo-protein added to form chylomicrons?
B48
41
24. Where are apo-proteins synthesized? Assembled? Where are chylomicrons secreted?
24. RER, assembled in golgi apparatus; chylomicrons secreted into lymph
42
25. If there is insufficient bile, what will happen?
25. steatorrhea, digestion proceeds but absorption compromised, clay colored stools because no bile pigments, deficient in fat soluble vitamins
43
26. What would cause insufficient pancreatic enzymes?
26. cystic fibrosis or pancreatitis
44
27. What drug inhibits gastric and pancreatic lipases, decreasing fat absorption by preventing TAG digestion?
orlistat
45
28. What drug inhibits NPC1L1, decreasing cholesterol absorption?
ezetimibe
46
29. What drug is resistant to lipase action, but has the taste and consistency of fat?
olestra
47
1. What are 4 things that compose human bile?
1. bile salts/acids 80%, phospholipids (PC) 16%, cholesterol 4%, minor constiuents
48
2. What is the committed and regulated step of bile acid synthesis? What does this do?
2. 7 alpha hydroxylase – adds OH to 7th carbon
49
3. What does the committed step of bile acid synthesis require?
3. NADPH, O2, cytochrome P450 (CYP7A), and vitamin C (ascorbate)
50
4. In the second step of bile salt formation, what is formed?
4. cholic acid (majority in humans) and chenodeoxycholic acid
51
5. What does the second step of bile formation require?
5. 12 alpha hydroxylase
52
6. What is step 3 of bile salt synthesis?
6. conjugation with taurine or glycine to yield 4 primary bile acids
53
7. This process in step 3 requires formation of what?
7. cholyl-coA and chenodeoxycholyl-coA
54
8. How are primary bile acids metabolized?
8. BA secreted into bile by liver with cholesterol (bile is alkaline so it is in salt form, aid in lipid digestion) OR some primary BA are metabolized by intestinal bacteria (deconjugation and 7 alpha dehydroxylation resulting in secondary BA)
55
9. What are two secondary bile acids?
9. deoxycholic acid and lithocholic acid
56
10. What happens to both primary and secondary BA? What is the exception?
10. both are reabsorbed (except lithocholic acid because of limited solubility) in ileum and returned to the liver to be conjugated and secreted.
57
12. What reaction does biliverdin reductase catalyze?
12. converts biliverdin to bilirubin which is transported through blood to the liver by albumin (high affinity for bilirubin)
58
11. What reaction does heme oxygenase catalyze?
11. converts heme from senescent RBCs to biliverdin
59
13. What happens to bilirubin in the liver? Then in the colon?
13. conjugated to diglucuronide, excreted through bile, goes to colon, converted to urobilinogen (colorless) by intestinal bacteria
60
14. How does bile get its pigments?
14. oxidation – urobilinogen when excreted through the urine turns to urobilin (yellow) and if urobilinogen is further metabolized it become stercobilinogen, which, when oxidized, becomes stercobilin (red-orange)
61
15. What type of jaundice causes an increase in total bilirubin production with increase in conjugated bilirubin, stool will be light colored, and urine will be dark brown?
15. post-hepatic jaundice
62
16. What type of jaundice causes an increase in total bilirubin with increase of unconjugated bilirubin, stools to be normal color and urine normal (both increased)
16. pre-hepatic jaundice
63
17. What type of jaundice causes an increase in total bilirubin with unconjugated bilirubin, stools to be light colored, and urine to have decreased urobilin?
17. hepatic jaundice
64
18. What makes unconjugated bilirubin more water soluble in neonates?
18. phototherapy/ photo induced isomerization
65
What is the role of mitochondria in triggering apoptosis?
cytochrome c escapes through the permeable membrane of mitochondria and activates Apaf-1 (apoptosis protease activating factor 1) which will cause it to form an apoptosome. This will find a procaspase and activate it to a caspase and apoptosis has begun
66
What is the mutation in LHON ( leber hereditary optic neuropathy)?
single base change in mitochondrial gene ND4 changes and Arg to His in polypeptide of complex 1 resulting in defective transfer of electron from NADH to ubiquinone
67
defective oxygen phosphorylation can lead to what?
less ATP concentrations and a rare form of DM
68
Is the L or D isomer of carbohydrates used in humans?
D isomer
69
cyclization of monosaccharides introduces what?
asymmetric carbon at carbon1
70
How do differentiate alpha or beta anomers
B anomer has OH group above the plane; alpha anomer has OH group below the plane
71
What is a glycoside?
two monosaccharides interacting at their anomeric carbons
72
How is a linkage indicated?
by orientation of anomeric carbon followed by numbers of 2 carbon atoms involved in the linkage ( ie alpha 1-4)
73
What glycosidic linkages form chains? Which ones branch?
a1-4 forms chains
| a1-6 branches
74
What are the three homopolysaccharides?
starch, glycogen, and cellulose
75
What are the three heteropolysaccharides?
chondroitin sulfate, hyaluronic acid, and heparin
76
What are glycoconjugates and what are examples of them?
carbs covalently attached to protein and lipid molecules (ex: proteoglycans, glycoproteins, and glycolipids)
77
What is the storage form of glucose in plants? What are two types?
amylose and amylopectin (branched)
78
What is the storage form of glucose in animals? How does it compare to amylopectin?
glycogen, more highly branched than amylopectin
79
What is the chief constituent in plant cell walls? How is it linked?
cellulose;
| B 1-4
80
What enzyme can break B1-4 linkages? Who doesnt have it?
cellulase;
| animals lack
81
What do heteropolysaccharides contain?
contain either of 2 modified sugars (N-acetylgalactosamine or N-acetylglucosamine) and contain a uronic acid (such as glucoronate or iduronate)
82
What monosaccharides do we eat in the diet?
fructose and glucose
83
What does digestion of carbohydrates require?
amylase and oligosaccharidases (mucosal brush border enzymes)
84
Amylase breaks only what kind of bonds?
a1-4
85
How are monosaccaharides absorbed by the intestinal lining?
facilitated diffusion
86
What are 5 brush border enzymes?
maltase, sucrase, isomaltase, lactase, and trehalase
87
How are monosaccharides transported to the liver?
through venous system capillaries
88
Lactose is converted to what two things by lactase?
galactose and glucose
89
Maltose is converted by maltase into what?
glucose
90
Sucrose is converted by sucrase into what?
fructose and glucose
91
How does glucose and galactose enter cells?
via Na carrier protein pump - pump will pump out 3 Na for every one coming in
92
How does fructose enter cells?
GLUT5
93
What glucose transport protein is associated with skeletal muscle?
GLUT4 as an insulin responsive transport
