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Phys Phinal (Annie & Lauren) 💩🚽 > Digestion And Absorption (Lauren) > Flashcards

Digestion And Absorption (Lauren) Flashcards

1
Q

When food gets to the digestive compartments, is it a size that we can absorb?

A

No, we need to break foodstuffs down into smaller sizes that can absorbed.

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2
Q

In a molecule of glycogen or starch, glucose molecules are linked to each other by ___,___ linkages and at branch points, there are ___,___ linkages

A

1,4 glucose to glucose

1,6 at branch points

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3
Q

How do we break down complex polysaccharides like glycogen and starch?

A

First break them into oligosaccharides

Then break down oligosaccharides into simple sugars (monosaccharides)

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4
Q

What kind of bonds can salivary amylase and pancreatic amylase break down?

A

1,4 only

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5
Q

What enzyme breaks down lactose?

A

Lactase

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6
Q

What enzymes break down Dextrins?

A

Maltase

Dextrinase

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7
Q

What enzymes break down maltotriose and maltose

A

Maltase

Sucrose

Dextrinase

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8
Q

What enzyme breaks down sucrose?

A

Sucrose

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9
Q

What are the products of lactose breakdown?

A

Glucose

Galactose

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10
Q

What are the products of sucrose breakdown?

A

Glucose

Fructose

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11
Q

What are the 2 main groups of enzymes that break down disaccharides and oligosaccharides

A

Galactosidases (Lactase)

a-glucosidases (sucrase, maltase, dextrinase)

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12
Q

What is another name for the enzymes that break down disaccharides and oligosaccharides into monosaccharides?

A

“Intrinsic membrane proteins”

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13
Q

How is glucose brought into the enterocyte from the lumen?

A

Secondary active transport

Comes in with the sodium gradient

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14
Q

What is the name of the transporter that brings glucose and galactose from the lumen across the apical membrane and into the enterocyte ?

A

SGLT 1

Comes in with SODIUM

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15
Q

Does SGLT1 use (active/secondary active/passive) transport to bring glucose and galactose into the enterocyte?

A

Secondary active

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16
Q

How does fructose get into the enterocyte

A

PASSIVE transport through the GLUT-5 transporter

(Don’t need active transport since there is so much more fructose in the lumen than inside the cell….it just diffuses down its gradient)

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17
Q

How do glucose and galactose travel across the basal membrane into the blood?

A

Facilitated diffusion using the GLUT-2 transporter

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18
Q

What is the main cause of disorders with carbohydrate digestion?

A

Enzyme deficiencies

Ex: lactase deficiency

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19
Q

Why do enzyme deficiencies cause you to “liquidate your assets” (aka diarrhea)

A

The unabsorbed carbs are osmotically active and hold water

🧻~~osmotic diarrhea~~
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20
Q

Is lactose intolerance congenital or acquired?

A

Its usually congenital (but not evident until later in life for many ppl)

Can also be caused by long-term disease that messes up membrane lactase

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21
Q

True or false: a significant amount of your protein intake comes from sloughed epithelial cells and gastric secretions

A

True 🍴

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22
Q

What are the products of protein digestion?

A

Amino acids

Oligopeptides

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23
Q

What enzyme needs to be activated FIRST before any other enzymes can be activated?

A

Trypsinogen must be turned into Trypsin by ENTEROPEPTIDASE**
*********

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24
Q

What enzymes does Trypsin activate?

A

Trypsinogen—> Trypsin

Chymotrypsinogen—> Chymotrypsin

Proelastase—> Elastase

Procarboxypeptidases A and B —> Carboxypeptidases A and B

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25
Q

What enzyme is required to activate Trypsin before any other enzymes can be activated

A

ENTEROPEPTIDASE

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26
Q

What happens to oligopeptidases when they get to the brush border?

A

Membrane bound peptidases will further break them down into AA’s

OR

Endocytosis of oligopeptides and immunoglobulins (from breast milk)**

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27
Q

When you’re a little baby drinking your mommy’s breast milk and you ingest immunoglobulins, how do you absorb those without first breaking them down into individual amino acids?

A

Brush border cells can use endocytosis to eat them WHOLE**

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28
Q

How do Amino acids get from the lumen into the enterocytes?

A

Secondary active transport coupled to sodium transport (just like glucose)

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29
Q

How do dipeptides and tripeptides get from the lumen into the enterocyte?

A

Coupled to H+ transport**

Once inside the cell, they will get further broken down by peptidases into amino acids

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30
Q

What co-transporters shuttle amino acids from the lumen into the enterocyte?

A

There are 4 separate ones depending on the type of amino acid:

Neutral AA’s

dibasic AA’s

Dicarboxylic AA’s

Imino (proline)

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31
Q

What are the 3 diseases that can cause problems with protein digestion/absorption?

A

Pancreatic insufficiency

Hartnup disease

Cystinuria

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32
Q

Why does pancreatic insufficiency inhibit protein absorption?

A

Insufficient amount of Trypsin= malnutrition

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33
Q

How does Hartnup disease affect protein absorption?

A

The transporter for neutral amino acids is defective

BUT you can still absorb di- and tripeptides via endocytosis, and those guys will have neutral amino acids in them.

👍 no big deal. no amino acid deficiency here

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34
Q

How does Cystinuria affect protein digestion/absorption?

A

Transporter for dibasic amino acids (cystine, lysine, and arginine) is absent from gut and kidney= dibasic amino acids lost in urine and feces

BUT di- and tripeptides can still be sucked up via endocytosis :)

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35
Q

What makes the digestion of fats so challenging?

A

Fats are not water soluble, but the enzymes needed to break them down are.

Fats also tend to coalesce so the surface area is small (reason we must churn and have bile emulsification)

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36
Q

What are the 4 key events in fat digestion?

A

Secretion of bile and lipases

Emulsification by bile

Hydrolysis of ester linkages

Solubilizing digestion products within micelles for delivery to enterocytes

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37
Q

What are the 3 specific enzymes needed for fat digestion?

A

Pancreatic lipase

Cholesterol ester hydrolase

Phospholipase A2

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38
Q

What does pancreatic lipase do?

A

Cleaves FA’s off triglycerades at the 1 and 3 position

39
Q

What protects pancreatic lipase from being destroyed by bile?

A

Colipase****

No colipase= no pancreatic lipase

40
Q

What does cholesterol ester hydrolase do?

A

Removes fatty acid from:

Cholesterol

Vitamin A, D, E,

Glycerine

(Non-specific esterase)

41
Q

What does Phospholipase A2 do?

A

Hydrolyzes phospholipids at the 2 position

42
Q

How do lipolytic products get through the intestinal mucosa?

A

Micelles diffuse through the “unstirred” later to the mucosal surface. Then they just diffuse right into the cells down their concentration gradient

43
Q

95% of fat is removed by the (small/large) intestine

A

Small

44
Q

Once all the pieces of triglycerides that were in the micelle diffuse into the cell, what happens to them?

A

They get reassembled into triglycerides and then turned into chylomicrons

45
Q

What happens to chylomicrons once they are produced inside the cell?

A

They get EXOCYTOSED across the basolateral membranes into a lacteal. It gets carried through the lymph system to the thoracic duct where it enters the general circulation

46
Q

What is a chylomicron?

A

A core of triglycerides surrounded by phospholipids and apoproteins

47
Q

How do micelles travel around the body?

A

THEY FUCKING DON’T!!!!

They are ONLY in the lumen of the intestine!

DO NOT MIX UP MICELLES AND CHYLOMICRONS

48
Q

What do chylomicrons do once they are in your bloodstream?

A

They deliver triglycerides to adipose and muscle

49
Q

What are the 4 ingredients in chylomicrons?

A

Triglycerides 84%**

Cholesterol 6%

Phospholipids 8%

Apoproteins 2%

50
Q

Zollinger-Ellison Syndrome is abnormal (digestion/absorption)

A

Digestion

51
Q

What happens with Zollinger-Ellison syndrome?

A

You have a tumor that secretes gastrin which causes the small intestine to be WAY TOO acidic.
All the acidity denatures pancreatic lipase and you can’t digest lipids.
(= lipids in feces=steatorrhea)

52
Q

Whipple’s Disease is abnormal (digestion/absorption)

A

Absorption

53
Q

What happens with Whipple’s disease?

A

Underdeveloped lymph system impairs the ability to pick up chylomicrons. Leads to steatorrhea

54
Q

Another name for enterokinase is________

A

Enteropeptidase

55
Q

Do these enzymes come from the small intestine or the pancreas:

Enterokinase

Disaccharidases

Maltase

Sucrase

Lactase

Peptidases

Aminooligopeptidase

Dipeptidase

A

Small intestine (they are membrane proteins)

56
Q

Do these enzymes come from the pancreas or the small intestine:
Amylase

Trypsin

Chymotrypsin

Carboxypeptidase

Elastase

Lipase-colipase

Phospholipase

A

Pancreas

57
Q

How do fat soluble vitamins travel through the lumen of the intestine?

A

Micelles

58
Q

If you had no micelles for some reason, would you have a vitamin deficiency?

A

Yes, you would not be able to absorb fat-soluble vitamins

59
Q

How do fat soluble vitamins enter the circulation?

A

In chylomicrons

60
Q

How do water-soluble vitamins get into the enterocytes?

A

Na+ dependent co-transport

Secondary active transport, just like glucose

61
Q

How does B12 get absorbed?

A

Bound to gastric intrinsic factor and then it gets absorbed in the ileum**

62
Q

What part of the intestine is B12 absorbed?

A

ILEUM

63
Q

Why is vitamin D required for calcium absorption?

A

It causes the expression of the Calcium binding protein which is the intracellular shuttle for Calcium- we don’t want a bunch of free calcium floating around inside cells

64
Q

How does calcium get across the brush border?

A

Facilitated diffusion

65
Q

How does calcium get across the basolateral membrane and into the blood?

A

TWO OPTIONS:

Ca+ ATPase

Na+/Ca+ exchanger

66
Q

What does gastric acid have to do with the intestinal absorption of Iron?

A

Helps absorption and with solubilization by reducing Fe3 into Fe2

67
Q

How does Iron travel around the blood

A

Transferrin

68
Q

How does iron get stored inside cells?

A

In ferritin

69
Q

If an enterocyte has a bunch of iron stored on ferritin, and then it gets sloughed off, what happens to the iron

A

You just poop it out

70
Q

Where is water reabsorbed?

A

Small intestine

Large intestine

NOT stomach

71
Q

What is the driving force for water reabsorption into enterocytes?

A

Water follows solutes out the basolateral membrane

72
Q

How does Na+ get pumped out of the enterocytes?

A

Na+/K+ ATPase

Requires A LOT of energy

73
Q

Water reabsorption is (isosmotic/hyposmotic)

A

Isosmotic

Water and solute absorption are proportional

74
Q

What part of the intestine is the #1 site for Na+ absorption?

A

Jejunum*

75
Q

How does Na+ get absorbed in the jejunum?

A

TWO OPTIONS:

Co transported with sugar or amino acid

Na+/H+ exchange (NHE)***

76
Q

What are the 2 important things that happen as a result of the Na-H+ exchanger in the jejunum?

A
  1. H+ that gets sent into the lumen neutralizes HCO3-
  2. Na+ floats through the cell and gets transported into the blood where it will combine with an HCO3- (that came from the production of the H+)
77
Q

In the jejunum, we end up with a net absorption of _______

A

NaHCO3
******

(From the Na and the HCO3- that get transported across the basolateral membrane)

78
Q

How does Cl- get absorbed in the jejunum?

A

Paracellular absorption driven by a voltage gradient

79
Q

What additional transporter is on the apical membrane of cells in the ILEUM?

A

Cl-/HCO3- exchanger
***

(Still have the NHE and the cotransporters for absorption of Na+)

80
Q

What transporter is present on the basolateral membrane in the jejunum and not the ileum?

A

HCO3- transporter

81
Q

What transporter is present on the basolateral membrane in the ileum and NOT in the jejunum?

A

Cl- transporter

82
Q

In the ileum, what happens to the acid/base status of the lumen?

A

Nothing, H+ and HCO3- are both secreted into the lumen

In the ileum we are not trying to recover bicarb, we’re trying to recover Cl-

83
Q

In the ileum there is a net reabsorption of

_________

A

NaCl****

84
Q

Net reabsorption

In Jejunum:

In Ileum:

A

In Jejunum: NaHCO3

In Ileum: NaCl

85
Q

What electrolyte gets absorbed in the colon and through what transporter?

A

Na+ gets absorbed through Epithelial Na+ Channels (ENaC)

86
Q

True or false: ENaC channels in the colon are sensitive to aldosterone like they are in the kidney

A

True

87
Q

What electrolyte gets secreted in the colon?

A

K+

88
Q

What will cause an increased amount of K+ to be secreted into the lumen in the colon?

A

Increased flow/diarrhea

Increased flow will increase Na+ absorption, which will kick out more K+

89
Q

Severe diarrhea puts you at risk of (hypo/hyper) kalemia

A

Hypo

90
Q

What 3 things get lost with diarrhea?

A

Fluid

HCO3-

K+

91
Q

Diarrhea puts you at risk for metabolic (acidosis/alkalosis)

A

Acidosis (loss of HCO3-)

92
Q

What are 3 possible causes of diarrhea?

A
  1. Decreased absorptive surface area (inflammation of small intestine)
  2. Osmotic diarrhea due to unabsorbable osmolytes (lactase deficiency, MgSO4 etc)
  3. Excessive secretion of intestinal fluid (Cholera)
93
Q

How does cholera cause diarrhea?

A

Cholera toxin binds to apical membrane of crypt cells, and causes adenylyl cyclease to go crazy making cAMP.

All the extra cAMP stimulates Cl- secretion, and water and Na+ will follow Cl-.

94
Q

How do you treat cholera?

A

Pedialyte

Phys Phinal (Annie & Lauren) 💩🚽 (4 decks)

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