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Block 1 - GI > Biochem > Flashcards

Biochem Flashcards

1
Q

Carbohydrates classification:

A

Monosaccharides (1)
Oligosaccharides (2-10)
Polysaccharides (>10)

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2
Q
  1. Same molecular formula, different structures

2. (1) with only one slight structural difference

A

Isomers

Epimers

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3
Q

Based on the functional group present in the sugar, they can be classified as :

A

Aldolase or Ketose

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4
Q

L-glucose isomers have a ___ group on the left. But only the __ configuration is found in the human body

A

Penultimate C-OH
D
*L is in bacteria

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5
Q

Aldoses

A

Mannose (hexose)
Galactose (hexose)
Glucose (hexose)
Ribose (pentose)

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6
Q

Ketohexoses

A

Fructose

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7
Q

Alpha vs Beta anomers

A

Beta-OH group of a sugar is above the plane of the ring

Alpha-Below

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8
Q

Glycosidic linkage is indicated by the orientation of the ____ followed by __

A

Anomeric carbon

Numbers of the two carbon atoms involved in the linkage

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9
Q

Two alpha-D-glucose molecules

alpha 1,4 glycosidic link

A

Maltose

*derived from starch

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10
Q

Alpha-D-glucose + beta-D-fructose

1,2 glycosidic linkage

A

Sucrose

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11
Q

Beta-D-galactose + alpha-D-glucose

Beta 1,4 glycosidic linkage

A

Lactose

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12
Q

2 types of starch

A
  1. Amylose: alpha 1,4 links
    - helix w/6 glucose per turns
  2. Amylopectin: alpha 1,4 and 1,6 links
    - branched
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13
Q

Which is more highly branched:

Glycogen or Amylopectin

A

Glycogen

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14
Q

Homopolysaccharide composed of
Beta-D-glucose units
Beta 1,4 linkage
(Humans lack the enzyme necessary to hydrolyze these links)

A

Cellulose

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15
Q

Long unbranched polysaccharides containing a repeating disaccharide unit
-they contain either of two modified sugars ____ or ___

A

Hereropolysaccharide

  1. N-acetylglucosamine (GlcNAc)
  2. N-acetylgalactosamine (GalNAc)
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16
Q

The most abundant heteropolysaccharides in the body are ___

A

Glycosaminoglycans (GAGs)

*Highly negatively charged molecules

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17
Q

Proteoglycans vs. Glycoproteins

A

P: 10% protein, 90% carbs
G: 90% protein, 10% carbs
-ex: antibodies, blood group antigens, hormones FSH, LH, and TSH

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18
Q

Glycolipids are present where?

A

Nerve tissues

Cell membrane

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19
Q

Dietary sources of carbs in order of most to least prevalent

A
  1. Starches
  2. Disaccharides
  3. Monosaccharides
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20
Q

Monosaccharides are absorbed by ___

A

Intestinal lining by facilitated diffusion

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21
Q
  1. Digestion of amylase requires ___

2. Digestion of oligosaccharides requires ___

A
  1. Salivary glands and pancreas

2. Mucosal brush border enzymes (maltase, sucrase, isomaltase, lactase, trehalase)

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22
Q

Maltase

  1. Activity
  2. Substrate
  3. Products
A
  1. Exoglucosidase, only alpha 1,4
  2. Malto-oligosaccharides
  3. Glucose
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23
Q

Sucrase

  1. Activity
  2. Substrate
  3. Products
A
  1. Hydrolyzes sucrose and maltase activity
  2. Sucrose Malto-oligosaccharides
  3. Glucose and fructose
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24
Q

Isomaltase

  1. Activity
  2. Substrate
  3. Products
A
  1. Alpha 1,6 bonds
  2. Alpha dextrins
  3. Glucose
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25
Q

Lactase

  1. Activity
  2. Substrate
  3. Products
A
  1. Beta glycosidase
  2. Lactose
  3. Glucose and galactose
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26
Q

Trehalase

  1. Activity
  2. Substrate
  3. Products
A
  1. Trehalose
  2. Trehalose
  3. Glucose
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27
Q

SGLT and GLUT

A

SGLT: Na+ couples glucose transporters
GLUT: Glucose transporter facilitators

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28
Q

GLUT
Skeletal muscle, heart, fat
Insulin responsive transport

A

GLUT 4

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29
Q

GLUT

neurons

A

GLUT 3

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30
Q

GLUT

small intestine, sperm, testes

A

GLUT 5

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31
Q

Digestion of proteins starts in the __

A

Stomach

  • due to pepsin and acid condition
  • continues in small intestine
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32
Q

pH of gastric juice is approximately __

Function?

A

2

Denatures protein
Kills bacteria
Activates pepsinogen

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33
Q

H+ secretion to stomach?

Cl-?

A

H+: CO2 and H2O

Cl-: through two membranes from the outside through parietal cells

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34
Q

What are the two ways to activate pepsinogen?

A
  1. Auto-activation at pH<5
  2. Pepsin activated
  3. HCl?
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35
Q

___ and ___ can both activate ___ cells to release Histamine

A

ACh
Gastrin
ECL

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36
Q

___ and ___ stimulate secretion of pancreatic digestive pro-enzymes and enteropeptidase from mucosal cells

A

CCK

Secretin

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37
Q

What does enteropeptidase do?

A

Activates trypsinogen to trypsin

38
Q

What does trypsin do?

A

Activates other pro-enzymes to active form

39
Q

Peptide bonds susceptible for chymotrypsin?

A 
Trp
Tyr 
Phe 
Met
Leu
40
Q

Peptide bonds susceptible for trypsin?

A

Arg

Lys

41
Q

Peptide bonds susceptible for elastase?

A

Ala
Gly
Ser

42
Q

Intestinal epithelial brush border peptidases:

These produce what?

A
  1. Endopeptidases
  2. Aminopeptidases
  3. Dipeptidases

-these produce free AAs and di- and tripeptides

43
Q

In the small intestine

  1. I cells secrete:
  2. S cells secrete:
  3. Duodenum secretes:
  4. Pancreas secretes:

What are the last two activated by?

A
  1. CCK
  2. Secretin
  3. Enteropeptidase (activated by CCK)
  4. Trypsinogen (activated by CCK and secretin)
44
Q

Pepsin

  1. Location
  2. Substrate
  3. Product
  4. Activated by
A
  1. Stomach
  2. Protein
  3. Peptides
  4. H+ or Pepsin
45
Q

Trypsin

  1. Location
  2. Substrate
  3. Product
  4. Activated by
A
  1. Small intestine
  2. Protein
  3. Peptides
  4. Enteropeptidase, trypsin
46
Q

Chymotrypsin, Elastase, and Carboxypeptidasea

  1. Location
  2. Substrate
  3. Product
  4. Activated by
A
  1. Small intestine
  2. Protein
  3. Peptide/aa
  4. Trypsin
47
Q

Endopeptidase, aminopeptidase, and dipeptidase

  1. Location
  2. Substrate
  3. Product
  4. Activated by
A
  1. Brush border
  2. Peptides
  3. aa, di- and tripeptides
  4. N/A
48
Q

Required protein intake

A

0.8g/kg body weight/day

49
Q

Essential amino acids

A

PVT TIM HALL

  1. Phe
  2. Val
  3. Thr
  4. Trp
  5. Ile
  6. Met
  7. His
  8. Arg (children)
  9. Leu
  10. Lys
50
Q

Amino acid metabolism

A

Either eliminated as urea or re-utilized to form another amino acid

51
Q

___ require contributions from lipids, carbs, and amino acids for metabolism.
___ require contributions from carbs and amino acids

A

Phospholipids

Nucleotides

52
Q

Positive vs. Negative nitrogen balance

A

+ intake>output (growth, convalescence)

  • output>intake (starvation, disease, burns)
53
Q

Lingual lipase, gastric lipase, pancreatic lipase activity

A

Fatty acids from positions 1 and 3 are removed, this leaves 2 FFA and one 2-monoacylglycerol

54
Q

Locations:
Lingual lipase
Gastric lipase
Pancreatic lipase

A

Mounts and stomach
Stomach
Small intestine

*absorption occurs in the jejunum

55
Q

___ is only active at the surface of the lipid droplet, so activity is slow

A

Lingual lipase

Gastric lipase

56
Q

___ is secreted along with pancreatic lipase. Lipase alone is inhibited by ___, so ___ binds lipase and prevents inhibition

A

Procolipase (converted to colipase by trypsin)
Bile salts
Colipase

57
Q

___ is secreted as a zymogen
Conversion of ___ to ___ is by trypsin.
Activity requires ___
Removed one FA molecule from the 2 position of phospholipids to yield ___ and ____

A

Phospholipase A2
Pro– to phospholipase A2
Bile salts
One FFA and one lysophospholipid

58
Q

Cholesterol esters are hydrolyzed to ___ and ___

A

Cholesterol and FFA

59
Q

Bile salts are produced in the ___ and derived from ___.

Example?

A

Liver
Cholesterol
Taurocholic acid

60
Q

These 3 compounds in bile can form micelles

A

Bile salts
Cholesterol
Phospholipid (mostly phosphatidylcholine)

61
Q

Mixed micelles contain:

A 
Bile salts
PC
Cholesterol
Products of lipid digestion 
Fat soluble vitamins from the diet
62
Q

____ and ___ fatty acids may be absorbed by the intestine without the help of bile salts

A

Short and medium chain

63
Q

3 proteins that play a role in sterol absorption

A

NPC1L1
SCARB1
CD36

64
Q

Intestinal epithelial cells contain ___ which pump sterols out of the cell. Examples?

A

ABC transporter proteins

ABCG5 and ABCG8

65
Q

Absorption of FFA and MAG vs dietary cholesterol

A

Virtually all of FFA and MAG are absorbed

-only 30-40% of dietary cholesterol is

66
Q

Bile salts are absorbed in the ___, where the lipids are repackaged as ___

A

Ileum

Chylomicron

67
Q

Long chain fatty acids bind to ___ or ___, then are transported to the ___ where they’re converted to ___

A

Intestinal FAB or FAB2
ER
Triacylglycerols

68
Q

Long chain FFAs are first converted to ___ by ___. Most triacylgylcerol is countryside by the ____ pathway. The remainder is synthesized by the ___ pathway

A

Fatty acyl CoA
Acyl CoA synthase
Monoacylglycerol
Phosphatidic acid

69
Q

Short and medium chain fatty acids enter the ___ as ____ then are transported to the the ___ bound to ___

A

Hepatic portal v.
FFA
Liver
Albumin

70
Q

Cholesterol is converted to cholesteryl ester by ___

A

Acyl CoA cholesterol acyltransferase

71
Q

The major apo-protein added to form chylomicrons is ___, which is produced in the ____. This is a splice variant of a gene also expressed in the ___, where the “full length” variant is produced. In the intestine it is ___ percent of that of the liver (hence the name)

A

B-48
ER
Liver
48

72
Q

Newly formed lipids and apo-proteins are assembled in the ___ to form the chylomicrons, which are then secreted into ___

A

Golgi

Lymph

73
Q

Composition of chylomicrons (in order of most to least amount)

A 
Triacylglycerol 
Phospholipid
Cholesterol ester
Protein 
Cholesterol
74
Q

Signs of lack of bile pigments

A

Clay colored stools

75
Q

___ is an inhibitor of gastric and pancreatic lipase. It reduced fat absorption by preventing ___ digestion. Side effects may be similar to ___

A

Orlistat

Triacylglycerol

76
Q

___ is octa-acyl sucrose (which is ___).
It is resistant to ___. It has the taste and consistency of fat, but is non-digestible.
If taking this, you should also take ___

A

Olestra
Lipase
Fat soluble vitamin supplements

77
Q

Ezetimibe inhibits ___ thus diminishes cholesterol absorption

A

NPC1L1

78
Q

Regulated step in bile acid synthesis

*It requires what?

A

7 alpha hydroxylase —> 7 alpha hydroxycholesterol

*NADPH, O2, CYP7A, Vit C (ascorbate)

79
Q

Formation of ___ requires 12 alpha hydroxylase.
The ___ is saturated.
___ is obtained from the carbons (C25-27) removed to form this
*these steps require __

A

Cholic acid
B ring
Propionyl-CoA
*NADPH, O2, CoA

80
Q

Both cholic acid and chenodeoxycholic acid are conjugated with ___ or ___

  • this years rods the four primary bile acids
  • this process requires formation of ___ and ___
A

Glycine
Taurine

  1. Taurocholic acid
  2. Glycocholic acid
  3. Taurochenodeoxycholic acid
  4. Glycochenodeoxycholic acid

*cholyl-CoA and chenodeoxycholyl-CoA

81
Q

Secondary bile acids are produced when ____

What are they?

A

Bile acids are metabolized by intestinal bacteria

  1. Deoxycholic acid
  2. Lithocholic acid
82
Q

Heme is converted to ____ by ___

This is the only known endogenous source of what?

A

Biliverdin
Heme oxygenase
CO

83
Q

Biliverdin is converted to ___ by ___

A

Bilirubin

Biliverdin reductase

84
Q

Bilirubin is transported through the blood to the ___ bound to ___

A

Liver

Albumin

85
Q

Bilirubin is conjugated to form a ___ in the liver, which is then excreted through ___. It is water soluble but poorly absorbed by intestinal mucosa. In the colon, it is converted to ___ by ____

A

Diglucuronide
Bile
Urobilinogen (colorless)
Bacteria

86
Q

What gives feces its color?

A

Urobilinogen is metabolized to stercobilinogen. Oxidation of stercobilinogen yields stercobilin, which is red-orange

87
Q

Jaundice is due to and increase in ____

A

Bilirubin

88
Q
  1. Prehepatic jaundice
  2. Hepatic jaundice
  3. Posthepatic jaundice
A
  1. Too much bilirubin produced, liver can’t conjugate all of it
  2. Liver can’t conjugate any bilirubin
  3. Regurgitation of conjugated bilirubin into blood (commonly an effect of gall bladder problems)
89
Q

Prehepatic jaundice

  1. Serum
  2. Stools
  3. Urine
A
  1. Increased total bili, increased unconjugated bili (indirect)
  2. Increased stercobilin excretion - normal color
  3. Increased urobilin excretion
90
Q

Hepatic jaundice

  1. Serum
  2. Stools
  3. Urine
A
  1. Increased total bili, increased unconjugated bili (indirect)
  2. Decreased stercobilin excretion - light color
  3. Decreased urobilin excretion
91
Q

Posthepatic jaundice

  1. Serum
  2. Stools
  3. Urine
A
  1. Increased total bili, increased conjugated bili (direct)
  2. Decreased stercobilin excretion - light color
  3. Decreased urobilin excretion - dark brown urine

Block 1 - GI (15 decks)

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