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Physiology Block III > Digestion & Absorption > Flashcards

Digestion & Absorption Flashcards

1
Q

The pH along the GI tract is mostly alkalytic, except it is acidic where?

A

Stomach

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2
Q

Besides villi on the mucosa, what other features increase SA?

A

Microvilli on the villi

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3
Q

What other things are located within the villi in the mucosa?

A

Blood vessels, Lacteals, Nerves (submucosal plexus)

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4
Q

How do the size of the villi change as we move through the GI tract?

A

Villi get shorter as we move through. SA is highest in proximal part of SI.

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5
Q

Is there villi in the LI?

A

NO

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6
Q

What structure is characteristic for BOTH SI and LI?

A

Crypts

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7
Q

What role do the crypts play?

A

Important role in regenerating epithelium. Contain stem cells

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8
Q

T/F. Turnover of epithelial cells is slow in GI.

A

FALSE. 17-70 billion cells are replaced every day

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9
Q

Entire GI tract is replaced in how many days?

A

5

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10
Q

Stem cells in the crypts can end up which fates?

A
  1. Absorptive cells

2. Secretory cells, either goblet or endocrine

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11
Q

What is an effect of impairment of stem cells in crypts?

A

Impaired absorption

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12
Q

What are the MONOMERS/absorbable pieces of CHO?

A

glucose, galactose, fructose

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13
Q

What are the MONOMERS/absorbable pieces of proteins?

A

AA, But can also absorb di and tri peptides

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14
Q

What are the MONOMERS/absorbable pieces of fats?

A

FA + monoglycerides + cholesterol, NOT TGs!

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15
Q

How do fats get through the PM?

A

Soluble in membrane - don’t need transporters

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16
Q

Even though we don’t need to worry about transport of fats, what else needs to be dealt with?

A

They have tendency to aggregate into big globs so need to be be able to get in there to break it down into individual components.

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17
Q

What are examples of POLYSACCHARIDES?

A

Starch, Cellulose (AKA FIBER)

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18
Q

In the MOUTH, STARCH + ________ =

A

Salivary Amylase

= Maltose + Glucose

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19
Q

In the DUODENUM, STARCH + ________ =

A 
Pancreatic Amylase (from Pancreas)
=Maltose + Glucose
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20
Q

What enzymes break down DISACCHARIDES? and where?

A

Hydrolytic Enzymes in the ILEUM (BRUSH BORDER). Located in microvilli itself –> GLYCOCALYX

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21
Q

What are the DISACCHARIDES and what are their monomers?

A

Sucrose –> Glucose + Fructose, Lactose –> Glucose + Galactose, Maltose –> Glucose x 2

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22
Q

Which PROTEIN ENZYMES are present in the STOMACH?

A

Pepsin

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23
Q

What PROTEIN ENZYMES are present in the DUODENUM?

A

Trypsin, Chymotrypsin, Carboxypeptidase

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24
Q

What PROTEIN ENZYMES are present in the ILEUM?

A

Aminopeptidase

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25
Q

What ENZYME is involved in FAT breakdown?

A

Pancreatic Lipase

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26
Q

Where is fat broken down into Monoglycerides and FAs?

A

Duodenum

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27
Q

T/F. Fiber can be broken down by enzymes

A

FALSE (will pass through undigested)

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28
Q

How does the epithelial cell get GLUCOSE INTO the cell?

A
  1. Gradient established by Na/K pump on BL side

2. Sodium-Glucose CO TRANSPORTER brings them in together

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29
Q

Do all the other MONOSACCHARIDES get into the cell the same way as glucose?

A

No. Fructose has to use GLUT5 facilitated transport

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30
Q

How do the MONOSACCHARIDES get OUT of the cell and into the BLOOD?

A

Facilitated diffused via GLUT2 transporters on BL membrane

31
Q

What happens with LACTASE production as we age?

A

Decreases

32
Q

What are 2 ways that lactase is inhibited?

A
  1. by glucose - “End product inhibition”

2. Intolerance

33
Q

T/F. There is no problem created if we fail to absorb all the glucose from the lumen in the small intestines.

A

FALSE. need the nutrients!

34
Q

Once peptides are broken down in stomach and duodenum, then are BROKEN DOWN FURTHER into ________, by: _________.

A

AMINO ACIDS by PROTEASES in duodenum and ileum.

35
Q

Where do protein PROTEASES come from?

A

Inactive/Zymogen from PANCREAS, then activated in intestinal LUMEN

36
Q

What is the first enzyme that becomes activated and then cleaves all the other enzymes into activity?

A

TRYPSIN

37
Q

How does trypsin get activated?

A

Enterokinase in the GLYCOCAYLX (this first cleavage gets it all going)

38
Q

How do we get the free AMINO ACIDS INTO the epithelial cell?

A

Co-transport with Sodium

39
Q

How do we get the PEPTIDES into the epithelial cell?

A

Secondary active transport coupled with PROTON gradient

40
Q

What has to happen to these peptides before they leave the epithelial cell?

A

Need to be broken down into AMINO ACIDS by PEPTIDASE before leaving via facilitated carrier

41
Q

Why is it important for protein digestion and absorption to take place in the FIRST part of the SI?

A

Don’t want any of them to get to LI or else will become gas and carries fluid with it

42
Q

Which protein exceptions are not broken down into AA and can be endocytosed and exocytosed in their complete form?

A

Mother’s antibodies in an infant (IgA)

43
Q

What happens if run out of protons to couple the transport of peptides?

A

generate more H via CARBONIC ANHYDRASE

44
Q

Which of the transporters are ESSENTIAL in luminal membrane for protein absorption?

a. Na-AA symporter
b. Na-H antiporter
c. Proton-peptide symporter
d. all of the above

A

D - all!

45
Q

What is the problem once the FA gets into the cell?

A

Due to water content, all the fat wants to GLOB TOGETHER - so will need to EMULSIFY it for lipase to be able to ACCESS it

46
Q

Most fat in a typical diet is in the form of:

A

TG

47
Q

What are the products of pancreatic lipase activity?

A

2 Free FA

1 monoglyceride

48
Q

T/F. There is no need for a transporter for free FA.

A

TRUE - can easily diffuse across membrane and into cell

49
Q

Emulsification of fat requires which 2 processes?

A
  1. Mechanical disruption

2. Emulsification

50
Q

Which organs do mechanical disruption of big fat globule?

A

Contractile activity of stomach and SI by segmentation and peristalsis

51
Q

What prevents the fat droplets from re-aggregating after mechanical disruption?

A

Bile salts and phospholipids in BILE

52
Q

What is bile composed of?

A

Bile salts - 50%, Phospholipids - 40%, Cholesterol - 4%, Bile pigments - 2%

53
Q

Where is bile stored?

A

GALLBLADDER

54
Q

What are MICELLES made up of?

A

FA, Monoglycerides –> NOT TG!, phospholipids, bile salts, VITAMINS

55
Q

How is bile transporter to the duodenum?

A

COMMON BILE DUCT

56
Q

What percent of bile is lost in feces and therefore replaced in the liver?

A

5%

57
Q

What is bile composed of?

A

Bile salts - 50%
Phospholipids - 40%
Cholesterol - 4%
Bile pigments - 2%

58
Q

What is the fat structure called after it leaves the Smooth ER and what else is added to it?

A

CHYLOMICRON - cholesterol, ApoB, vitamins too (NOT FREE FA)

59
Q

How does the chylomicron get OUT?

A

Processed by golgi and eventually fuse with PM releasing (EXOCYTOSE) the chylomicron into the Interstial fluid to enter the LACTEALS

60
Q

What do Micelles have that emulsion droplets DO NOT?

A

Bile salts and phospholipids

61
Q

Beside B6 (which is absorbed via diffusion), which vitamin does NOT get absorbed via Mediated transport?

A

B12 - too large and too charged a molecule. But bind to INTRINSIC factor before being endocytosed.

62
Q

What are the fat-soluble vitamins?

A

A D E K

63
Q

What is an implication of missing pieces of your gut in regards to vitamin absorption?

A

There are DIFFERENT SITES of absorption for the water-soluble vits

64
Q

Where does INTRINSIC FACTOR come from?

A

secreted by gastric PARIETAL Cells

65
Q

Beside B6 (which is absorbed via diffusion), which vitamin does get absorbed via Mediated transport?

A

B12 - too large and too charged a molecule. But bind to INTRINSIC factor before being endocytosed.

66
Q

Inside the enterocyte, B12 binds to what to enter portal blood:

A

Transcolbalamin II

67
Q

Fat-soluble vitamins NEED CARRIERS in circulation, what are they?

A

A: in chylomicorn
D: binding protein before conversion in liver
E: lipoproteins and RBCs
K: VLDL

68
Q

Where in the SI does B12 + IF get endocytosed?

A

LOWER portion of ILEUM

69
Q

Where is CALCIUM absorption REGULATED?

A

Duodenum and jejunum

69
Q

How is IRON absorption REGULATED?

A

intracellular binding with PROTEIN and FERRITIN

69
Q

If want MORE Ca to come across, then what happens?

A

Increase BINDING PROTEINS inside cell = CALBINDIN

69
Q

What happens when we have LOW IRON content in BLOOD?

A

Opposite process, DECREASE FERRITIN –> lets iron go, and IRON MOVES OUT into blood

69
Q

How is the amount calbindin determined?

A

by Vitamin D

69
Q

What happens when we have HIGH IRON content OUTSIDE in the blood?

A

Will stimulate production of FERRITIN inside cell which BINDS IRON and doesn’t move it out –> FECES

Physiology Block III (8 decks)

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