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Phys 3…Ash, Heather, Alyssa > GI digestion & absorption > Flashcards

GI digestion & absorption Flashcards

1
Q

What is the area of the intestines and lungs?

A

Tennis court - 300 sq meters

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2
Q

What is the function of a lacteal?

A

Absorption of fats in a villus

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3
Q

What are the roles of nerves in villi?

A

To get sensory info (mechanical, chemical) coming in from the villus; to give motor instructions for secreting substances

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4
Q

Which enteric nerve layer are the nerves of the villi derived from?

A

submucosal plexus

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5
Q

Which segment of the small intestine has the least absorptive ability?

A

ileum - less surface area than the duodenum & jejunum

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6
Q

Villi are found throughout the GI tract.

T/F

A

False - villi are exclusive to small intestine.

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7
Q

Crypts are common to small intestine and large intestine.

T/F

A

True - crypts are necessary for cell turnover

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8
Q

“Fiber” refers to a complex polysaccharide (carbohydrate) that cannot be broken down by enzymes.

T/F

A

True

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9
Q

How are glucose and galactose transported across the intestinal epithelium?

A

Secondary active transport, SGLT1

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10
Q

How is fructose transported across the intestinal epithelium?

What is necessary for this to happen?

A

Facilitated transport, GLUT5 - is dependent on a fructose gradient, so as soon as fructose is brought into the cell it is pumped out to the interstitial fluid side

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11
Q

How do glucose, galactose, and fructose leave intestinal epithelial cell to the interstitial fluid side?

A

facilitated diffusion transporters in the basolateral membrane, GLUT2

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12
Q

What causes lactose intolerance?

A

Lactase brush-border enzymes are missing or decreased….lactose stays in the lumen. It’s osmotically active, so it draws water into the lumen (diarrhea). Also, it provides a sugar supply to the bacteria in the large intestine, and they create gas as they anaerobically metabolize it.

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13
Q

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

T/F

A

False. Passing on any nutrient source to the large intestines can be a problem (cellulose is not a nutrient source - it’s indigestible).

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14
Q

Enzymes and their locations of actions?

Starch

A

salivary amylase - mouth

pancreatic amylase - duodenum

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15
Q

Enzymes and their locations of actions?

Cellulose

A

NONE - NOT DIGESTED

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16
Q

Enzymes and their locations of actions?

Disaccharides

A

hydrolytic enzymes in ileum

17
Q

Enzymes and their locations of actions?

Proteins

A

pepsin - stomach

trypsin - duodenum

chymotrypsin - duodenum

carboxypeptidase - duodenum

aminopeptidase - ileum

18
Q

Pancreas releases trypsin, chymotrypsin, carboxypeptidase, and aminopeptidase.

T/F

A

FALSE! Pancreas releases inactive versions of these enzymes, so that we don’t start digesting ourselves.

trypsinogen

chymotrypsinogen

procarboxypeptidase

proaminopeptidase

19
Q

All of the proteolytic enzymes result in peptide fragments.

T/F

A

FALSE

the peptidases result in free amino acids

20
Q

Enzymes and their locations of actions?

triacylglycerol

A

pancreatic lipase - duodenum

21
Q

How do amino acids enter the intestinal epithelium?

A

Via co-transport with sodium

22
Q

How are peptide fragments brought into the intestinal epithelium?

A

absorbed by secondary active transport coupled to H+ gradient

23
Q

How do peptides leave the intestinal epithelial cells?

A

di- and tri-peptides are hydrolyzed to amino acids before leaving cell in facilitated diffusion carrier

24
Q

The components of a micelle include all of the following EXCEPT:

A. Bile salt

B. Triglycerides

C. Phospholipid

D. Fatty acids

A

B - Micelles do not contain triglycerides.

25
Q

Why are free fatty acids and monoglycerides converted back into triglycerides within the epithelial cell?

A

To maintain a steep concentration gradient

26
Q

The components of a chylomicron include all of the following EXCEPT:

A. Cholesterol

B. Triglycerides

C. Phospholipid

D. Fatty acids

A

D - Fatty acids

27
Q

How & where is vitamin B12 absorbed?

A

Vitamin B12 is too large and is a charged molecule. It must bind to intrinsic factor protein before being endocytosed by epithelium in lower portion of ileum.

28
Q

Emulsification

A

Prevents small fat droplets from reaggregating in the intestinal lumen. This is achieved by the action of bile salts and phospholipids present in bile (from liver).

29
Q

Describe the process of fat absorption starting with emulsified fatty acids.

A

~fatty acids move into cell

~fatty acids form triglycerides

~triglycerides form a chylomicron inside the cell

~chylomicrons are exocytosed to the interstitium and enter lacteals and portal system.

30
Q

How are fat-soluble vitamins absorbed?

A

Fat-soluble vitamins are solubilized in micelles and are absorbed with fatty acids & monoglycerides into chylomicrons.

31
Q

Protein digestion and absorption is completed in the _____ portion of small intestines (upper, lower)

A

upper

32
Q

How are water-soluble vitamins absorbed (in general)?

A

Water-soluble vitamins are absorbed by diffusion or mediated transport except vitamin B12.

33
Q

What are the circulation forms of the fat-soluble vitamins?

A
  • Vit. A (retinol) converted to ester for incorporation into chylomicron
  • Vit. D (calciferol) transferred to binding protein before conversion in liver
  • Vit. E (a-tocopherol) transported with lipoproteins and erythrocytes
  • Vit. K is incorporated in VLDL in liver
34
Q

Where is intrinsic factor secreted?

A

secreted by gastric parietal cells into lumen of tract - it’s not in the blood

35
Q

We absorb all of the calcium and iron that we eat.

T/F

A

False. Absorption of these minerals is regulated.

36
Q

How do mother’s IgA antibodies get into the fetus?

A

endocytosis/exocytosis of intact IgA

37
Q

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

A. Sodium-amino acid symporter

B. Sodium-proton antiporter

C. Proton-peptide symporter

D. All of above are essential

A

All

38
Q

What are the products of pancreatic lipase activity?

A

2 free fatty acids

1 monoglyceride

39
Q

How do we increase our absorption of iron?

A

Stop producing the iron-binding molecule (when it’s bound, it gets sloughed off and pooped out).

Phys 3…Ash, Heather, Alyssa (10 decks)

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