Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GIGU > 12. Digestion and Absorption in the Gastrointestinal Tract > Flashcards

12. Digestion and Absorption in the Gastrointestinal Tract Flashcards

1
Q

Why are enterocytes susceptible to radiation and chemotherapy?

A

Because they have a turnover rate of only 3 to 6 days.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the major mechanism of uptake in the G.I. for protein and fats?

A

Pinocytosis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What to essential molecules lose their ability to be absorbed s/p terminal ileum resection?

A

Vitamin B12.

Bile salts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does starch initially break down into?

A

Maltose and 3-9 polymers of glucose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do maltose and trehalose breakdown into?

A

Glucose + Glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does lactose break down into?

A

Glucose + Galactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does sucrose break down into?

A

Glucose + Fructose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What transporter pulls glucose and galactose from the luminal side of the enterocytes?

A

SGLT1

Secondary Active Transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What transporters are used to pump glucose, galactose, and fructose out of the basolateral side of the enterocyte into the blood?

A

GLUT2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why does consumption of lactose by the lactose intolerant result in bloating and flatulence?

A

Because the lactose is instead fermented by the commensal flora of the G.I.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How much D-xylose must be present after five hours in order to be considered “normal absorption.”

A

4 g or more.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the method of absorption of D-xylose at the dose used in the D-xylose absorption test?

A

Passive absorption.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What portion of the digestion of proteins is not essential to maintain homeostasis?

A

The portion of protein digestion that occurs in the stomach. Namely, the activity of pepsin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What enzymes are secreted by the pancreas to digest proteins?

A

Trypsin and chymotrypsin (enteropeptidases).

Carboxypeptidase A and carboxypeptidase B (exopeptidases).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which of the proteolytic enzymes of the pancreas are responsible for breaking down large proteins into small polypeptides?

A

Trypsin and chymotrypsin (the endopeptidases).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What converts trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase A, and procarboxypeptidase B into their active forms?

A

Trypsin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Besides trypsin, what converts trypsinogen into its active form?

A

Enterokinase from the brush border.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do amino acids enter the enterocytes?

A

Via a Na+-amino acid transporter specific to the type of the amino acid (neutral, acidic, basic, imino).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens to dipeptides and tripeptides that enter the enterocytes?

A

They are either broken down by cytosolic peptidases and secreted as such, or they enter the portal system whole.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do amino acids exit the basolateral side of the enterocytes?

A

Via facilitated transport (not using sodium) with a transporter specific to the type of each amino acid (acidic, neutral, basic, imino).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How will chronic pancreatitis or cystic fibrosis affect protein digestion?

A

It will cause deficiency of all pancreatic enzymes, including all of the proteases (trypsin, chymotrypsin, carboxypeptidase A & B) which are essential for the breakdown of proteins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the basic pathophysiology of cystinuria?

A

Defect or absence of the dibasic amino acid transporter. This results in a deficiency in the COAL amino acids (cystine, ornithine, arginine, lysine) in the body and their accumulation in the urine. Cystine then forms crystals, presenting like kidney stones.

23
Q

What is the basic pathophysiology of Hartnup disease?

A

Deficiency of pancreatic enzymes or defect in transporters of intestinal epithelial cells for neutral amino acids.

Presents like pellagra – dementia, diarrhea, dermatitis.

24
Q

How would cystic fibrosis result in steatorrhea?

A

Anything that creates an inability of the duodenum to increase the pH of the chyme will prevent the action of lipases, amylases, and peptidases.

Cystic fibrosis prevents the pancreas from releasing bicarbonate.

25
Q

What is the primary dietary form of fat?

A

Triglycerides.

26
Q

What serves to emulsify fats in the stomach?

A

Dietary proteins.

27
Q

What is the function of colipase?

A

Colipase binds to pancreatic lipase and displaces bile salts.

28
Q

Which fat digesting enzymes are secreted in their active form by the pancreas?

A

Pancreatic lipase.

Cholesterol ester hydrolyze.

29
Q

What enzyme is responsible for the breakdown of cholesterol esters?

What organ secretes it?

A

Cholesterol ester hydrolase.

The pancreas.

30
Q

How does cholecystokinin assist with the absorption of fats?

A

Delays gastric emptying, stimulates bile salt ejection, and indirectly increases the pH of the lumen via potentiating secretin.

31
Q

What pancreatic enzyme is responsible for phospholipid breakdown?

What other enzyme activates it?

A

Phospholipase A2.

Trypsin.

32
Q

What are the steps of fat absorption?

A
  1. Solubilization by micelles
  2. Diffusion of micellar content across apical membrane
  3. Re-esterification
  4. Chylomicron formation
  5. Exocytosis of chylomicrons into lymphatics
33
Q

Why might small intestinal bacterial overgrowth (SIBO) interfere with fat digestion and absorption?

A

Small intestinal bacteria deconjugate bile salts. If this occurs too significantly fat cannot be absorbed properly.

34
Q

What are the two main causes of small intestinal bacterial overgrowth (SIBO)?

A

Increase intestinal pH due to diminished gastric secretions and small intestine dysmotility.

35
Q

What is “tropical sprue?”

A

A loss of or decreased the number of intestinal epithelial cells.

Reduced microvilli surface area causes a diminished lipid absorption – which causes steatorrhea as well as folate and vitamin B12 deficiency.

36
Q

What is caused by celiac sprue?

A

Destruction of small intestine villi.

Hyperplasia of the intestinal crypts.

Malabsorption of folate, iron, calcium, and vitamins A, B12, and D.

37
Q

How are most vitamins absorbed?

A

Via sodium dependent cotransport.

38
Q

What can be caused by small intestine bacterial overgrowth overall?

A

Pain, bloating, gas, diarrhea/constipation.

Malabsorption issues – steatorrhea and vitamin/mineral deficiency.

Improper lipase activity due to changes in pH.

39
Q

What is the diagnostic test for small intestine bacterial overgrowth (SIBO)?

A

Methane/hydrogen breath test.

40
Q

What is the function of vitamin B12?

A

Acts as a coenzyme for reducing ribonucleotides to deoxyribonucleotides.

Cofactor in folate coenzyme recycling.

Cofactor in nerve myelination.

41
Q

Besides resection or damage to the ileum, what two diseases can result in a vitamin B12 deficiency?

A

Atrophic gastritis and autoimmune metaplastic atrophic gastritis, both of which result in a decrease of functional intrinsic factor produced.

42
Q

What other nutrient does calcium absorption require to be effective?

A

Vitamin D (1,25 dihydroxycholecalciferol)

43
Q

What is transferrin, and how is it formed?

A

Transferrin is the absorbed form of free iron.
Apotransferrin in the bile enters the duodenum and binds free iron and hemoglobin. This forms transferrin which can then be absorbed into epithelial cells via pinocytosis.

44
Q

How does vitamin C play a role in iron absorption?

A

It is essential for ferric reductase, which reduces nonheme iron so it can be absorbed.

45
Q

What transports fructose on the apical and basolateral sides of enterocytes?

A

The apical side uses GLUT5 and of the basolateral side uses GLUT2.

46
Q

What is one common theme between zollinger-ellison and pancreatitis?

A

Improper acidity of duodenum contents

47
Q

What causes pernicious anemia?

A

Failure of RBC maturation when vitamin B12 is deficient

48
Q

How does Vitamin D contribute to calcium absorption?

A

7-dehydrocholesterol is converted into cholecalciferol

End result in kidney is 1,25 dihydroxy-D3 which leads to Ca2+ absoprtion, bone calcification, and bone resorption

49
Q

What is the role of the jejunum in regards to electrolytes?

A

Absorption of Na+ and HCO3- into the blood

H+ into the lumen

50
Q

What is the role in regards to the ileum in regards to electrolytes?

A

Absorption of Na+ and Cl- into the blood

H+ and HCO3- into the lumen

51
Q

What is the role of the colon in regards to electolyte absorption?

A

Na+ aborption and K+ secretion

Aldosterone promotes Na+ absorption

Na+/K+ creates gradient for K+ in the cell which causes secretion of K+ into the lumen

52
Q

How does cholera affect electrolyte absoprtion?

A

Cholera increases cAMP resulting in increased Cl- secretion

Cl- secretion is accompanied by Na+ and H2O

Volume of fluid secreted overwhelms the absorptive mechanism of the small intestine and colon which leads to massive diarrhea

53
Q

How is iron absorbed?

A

Absorption is in the small intestine

Fe3+ reduced to Fe2+

Binds to apoferritin in the intestinal cells; binds to transferrin in blood

54
Q

What receptor brings in fructose on the luminal side of the small intestine?

A

GLUT5

via facilitated diffusion

GIGU (40 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions