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Gastrointestinal > Biochem of the GI tract > Flashcards

Biochem of the GI tract Flashcards

1
Q

What is the enzyme in the mouth that aids in digesting starch? Lipids?

A

alpha amylase

Lingual lipase

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2
Q

What is the zymogen secreted by the stomach that aids in food digestion and turning on other enzymes?

A

Pepsinogen

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3
Q

What activates pepsinogen?

A

low pH

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4
Q

What cells in the stomach secrete pepsinogen?

A

Chief cells

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5
Q

What is the enzyme secreted by the pancreas that is secreted in its active form?

A

Pancreatic alpha amylase

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6
Q

What are the two mineral chemical secreted by the pancrase?

A

NaCl

NaHCO3

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7
Q

The liver synthesizes bile acids from what?

A

Cholesterol

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8
Q

Where are the enzymes that convert carbs and proteins into absorbable low molecular weight molecules?

A

Brush border of the intestines

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9
Q

What form must carbs be in to be absorbed into the intestines?

A

Monosaccharides

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10
Q

What are the two monomers of sucrose?

A

Glu and fructose

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11
Q

What are the two monomers of lactose?

A

Galactose and glucose

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12
Q

What are the two monomers in amylose? What is the linkage here?

A

Galactose and glucose

alpha 1,4

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13
Q

What are the monomers in amylopectin? What is the linkage here?

A

Glucose glucose

alpha 1,4 and alpha 1,6 branches

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14
Q

What are the monomers in glycogen? What is the linkage here?

A

Glc-glc

alpha 1,6

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15
Q

What are the monomers in cellulose? What is the linkage here?

A

glucose glucose

beta 1,4

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16
Q

Animal is to glycogen as plant is to what?

A

Amylopectin

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17
Q

Where does starch digestion begin? What enzymes? What are the bonds that are being broken?

A

Mouth
salivary endosaccharidase alpha-amylase

non-terminal alpha 1,4 linkages

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18
Q

What limits the digestion of molecules in the mouth?

A

Need acidic condition of the stomach to denature stuffs

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19
Q

What are the ends products of pancreatic amylase digestion? (3)

A

Maltose
Maltotriose
Alpha-limit dextrans

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20
Q

Why can’t cellulose be digested?

A

Humans lack the beta-1,4 enzyme

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21
Q

Lactose is hydrolyzed into glucose and galactose by what enzyme?

A

Lactase

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22
Q

Maltose is hydrolyzed to two glucose molecules by what enzyme?

A

Maltase

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23
Q

Sucrose is split into glucose and fructose by what?

A

Sucrase/isomaltase complex

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24
Q

What is the transporter in the small intestines that picks up glucose? What the means by which this happens?

A

SGLT-1

Na/glucose transporter that utilizes Na gradient from Na/K ATPase

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25
Q

What is the transporter in the small intestines that picks up fructose? What is the means by which this happens?

A

GLUT5

Facilitated diffusion

26
Q

Once inside the cell, monosaccharides are transported into

the circulation through the plasma membrane how? What is the transporter protein utilized here?

A

Through contra-luminal facilitated diffusion (GLUT2)

27
Q

What is the cause of lactose intolerance?

A

Primary lactase non-persistence is the decline in lactase as we age

28
Q

What does the breath test for Lactose intolerance measure?

A

H2 in the breath from bacterial digestion of lactose

29
Q

What are the four enzymes produced by the pancreas that pepsin activates?

A

Trypsin
Chymotrypsin
Elastase
Carboxypeptidase

30
Q

Besides activating other enzymes, what is the role of pepsin?

A

Degrade proteins

31
Q

Where does the bulk of protein digestion occur?

A

small intestines

32
Q

What form must protein be in to be absorbed?

A

di and tri peptides (or free amino acids)

33
Q

What are the three active enzymes in the intestinal brush border that are involved in protein digestion?

A

Aminopeptidase
Dipeptidase
Endopeptidase

34
Q

What are the two broad categories of pancreatic proteases?

A

Endoproteases

Exoproteases

35
Q

What are the three endoproteases?

A

Trypsin
Chymotrypsin
Elastase

36
Q

What is the one exoprotease?

A

Carboxypeptidase

37
Q

Activation of zymogens (besides pepsin) is activated by what? Where does this occur? What is the first step in the process?

A

Endopeptidases located in the luminal plasma membrane of the intestinal enterocytes

First step = conversion of trypsinogen to trypsin

38
Q

What is the role of cholecystokinin?

A

Stimulate the secretion of endopeptidases from the intestinal mucosa and trypsinogen from acinar cells of the pancreas

39
Q

What is the role of the acinar cells of the pancrease? What is the chemical signal that they respond to?

A

Secretion of trypsinogen in response to CCK release

40
Q

The digestion of most of the di and tri peptides in the intestines is completed where?

A

intracellularly in the Enterocytes

41
Q

What is issue with pancreatic duct blockage?

A

Leads to autodigestion of the pancreas via pancreatic enzymes

42
Q

What is the cause of CF?

A

mutations in the gene encoding

the CFTR protein

43
Q

What is the pancreatic issue associated with CF?

A

Reduce the production of sodium bicarbonate, leading to dehydration and thickening of the pancreatic juice/mucus. The consequence of this is to reduce the production of pancreatic digestive enzymes and in severe cases cause blockages in the lumen and the duct.

44
Q

What is the cause of celiac disease?

A

In celiac disease a peptidase defect
leads to the appearance of small peptides in the intestine that are
toxic to mucosal cells

45
Q

What is Hartnup disease?

A

Inability to absorb Tryptophan d/t defective transport leading to CNS symptoms and ataxia from loss of NAD

46
Q

What is the cause of cystinuria?

A

Defects in transport for Cystine, K, R, and ornithine. Causes persistent renal calculi

47
Q

The majority of the digestion of lipids is carried out by what enzyme?

A

Pancreatic lipase

48
Q

What is the apolipoprotein that provide chylomicrons their structure?

A

B48

49
Q

What are the possible causes of steatorrhea?

A
  • Disruption of lipid absorption or digestion
  • Defective pancreatic function
  • Cholestyramine
50
Q

What is the enzyme that phosphorylates glucose when it enters a cell? Why does it do this?

A

Hexokinase

To keep glucose in the cell, and to start glycolysis

51
Q

What is the order of the transporters for Glucose uptake? Fructose?

A

Glucose = SGLT1 to GLUT2

Fructose = GLUT5 to GLUT2

52
Q

Where is GLUT2 found?

A

On the basolateral cellular membrane of the enterocyte

53
Q

What is the role of CCK?

A

Activates intestinal mucosal cells and pancreatic acinar cells to produce enteropeptidase and trypsinogen respectively

54
Q

What is the importance of HCl?

A

Denature proteins to make them available for enzymatic action

55
Q

What is the role of trypsin inhibitor?

A

Prevents the premature activation of trypsin in the pancrease by blocking the active site, to stop autodigestion

56
Q

Why are amino uptake disorders rare?

A

A lot of overlap between different transporters for amino acids

57
Q

Where are the two major locations of amino acid transporters?

A

Intestinal lumen

Renal membranes

58
Q

What is the major chemical reaction that pancreatic lipase is needed for?

A

Cleavage of 2FAs from a TAG to allow fats in micelles to enter cytoplasm. This is then resynthesized into TAG and put into chylomicrons

59
Q

What is the drug that binds bile salts in the intestines to lower cholesterol?

A

Cholestyramine

60
Q

What is the relationship between colon cancer, bile salt, and bacteria?

A

Some bacteria can modify bile salts into steroids, causing overproliferation of cells, and thus causing colon cancer

Gastrointestinal (42 decks)

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