Brainscape's Knowledge GenomeTM

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


See full index

Biochemistry (books and trans) > Electrolyte secretion and absorption (partial) > Flashcards

Electrolyte secretion and absorption (partial) Flashcards

1
Q

Mucosal protection in the duodenum is dependent on this duodenal secretion

A

HCO3

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

Toward the lumenal pole of epithelial cells are found the apical junction complexes which comprises what kind of junctions (2)

A

Tight junctions and adherens junctions

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

In the apical junction complexes, these are basally located structures and are characterized by a high level of E-cadherin

A

adherens junctions

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

True or false

Tight junction permeability is constant along the length of the intestinal tract

A

False

    • Tight junction permeability is not constant along the length of the intestinal tract and generally decreases aborally
    • Thus, the epithelium of the proximal small intestine is considered to be leaky, whereas that of the colon is considered to be tight
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Transmembrane components of the tight junctions include (3)

A

occludin, claudins, and junctional adhesion molecules (JAMs)

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

Constitute the barrier-forming components of tight junctions and are responsible for dictating the size and ionic permeability of the paracellular pores

A

Claudins

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

These cells perform the absorptive and secretory functions of the intestine

A

Enterocytes

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

Fluid secretion predominantly occurs in the _____region, whereas absorption mainly occurs across the _____

A

Crypt, villus cells

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

These cells in the crypt region secrete mucus that lubricates and protects the epithelial surface

A

Goblet cells

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

These cells play an important role in host defense by secreting antibacterial peptides, such as lysozyme and defensins and are located toward the base of the crypts

A

Paneth cells

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

HCO3 secretion is highest in what part of the intestine?

A

Proximal small intestine

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

Na+ absorption is mediated by electroneutral transport in what part of the intestine?

A

Proximal colon

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

Electrogenic Na+ absorption through the epithelial Na+ channel predominates in what part of the intestine?

A

Distal colon

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

Na+ absorption occurs predominantly through nutrient coupled pathways in what region of the intestine?

A

Proximal small intestine

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

This kind of transport moves net charge across the membrane by the flux of either single ions or combinations of transport substrates whose charges are unequal

A

Electrogenic

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

This kind of transport mediate a net flux of ions, but do so without moving net charge across the membrane during a transport cycle

A

Electroneutral
** Electroneutral transporters may mediate an exchange of equal charges across the membrane (Na+/H+ exchanger) or a cotransport of equal and opposite charges (Na+/K+/2Cl− cotransporter)

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

This kind of transport is often a compensatory mechanism that opposes the electrical gradient established by the action of electrogenic transporters thereby maintaining a electrical neutrality

A

Paracellular transport

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

Driving force affecting electroneutral carriers

A

Chemical gradient

**not ELECTRICAL gradient

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

In the presence of Mg2+, catalyzes the efflux of three Na+ ions from the cell and the uptake of two K+ ions at the expense of hydrolyzing one ATP molecule per cycle

A

Na+,K+-ATPase

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

True or false

Na+,K+-ATPase is electroneutral

A

False

** More cation is pumped out than is replaced thus electrogenic

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

Na+,K+-ATPase is localized ______

A

Basolaterally

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

Protons secreted by the colonic H+,K+-ATPase are important for stimulating uptake of what luminal content?

A

Short chain fatty acids (SCFAs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Many food-derived products including glucose, amino acids, and vitamins, as well as endogenous luminal solutes such as bile acids, are taken up by what transport protein?

A

Specific Na+-coupled cotransport proteins – in the apical membrane of enterocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Each transport cycle of SGLT1 results in ____

A

Uptake of two Naions and one glucose molecule (electrogenic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Expressed in the apical membrane of cells in the small intestine and can transport a wide variety of dipeptides and tripeptides

A

Proton-coupled peptide cotransporter (PEPT1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

PEPT1 transports uncharged peptide substrates from the lumen in together with protons (1:1), what transport mechanism is responsible for supplying the protons?

A

Na+/H+ exchanger NHE3

  • *Na inside the cell, H outside the cell
  • *H coupled with peptides goes inside the cell
  • *expressed preferentially on the villus in the small intestine and on the surface and in the upper one-third of the colonic crypts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

This cotransporter is part of transcellular SCFA absorption, in which it is the route for basolateral SCFA flux from cells to the blood stream

A

Proton-coupled monocarboxylate cotransporter

MCT1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

This cotransporter plays a key role in Cl− secretion as it provides the predominant route for basolateral Cl− uptake, and it also participates in K+ secretion by providing a second route for basolateral K+ uptake in addition to the activity of the Na+,K+-ATPase

A

The Na+/K+/2Cl−

    • This cotransport is electroneutral because each transport cycle moves equal numbers of cations (one Na+ plus one K+) and anions (two Cl−) into the cell
  • *predominantly in the colon rather than the small intestine
29
Q

This isoform of Na+/H+ exchanger is present in virtually all cells of the body and is believed to be responsible for cellular pH regulation

A

NHE1

30
Q

This isoform of Na+/H+ exchanger is found in the basolateral membrane of intestinal epithelial cells

A

NHE1
** NHE2 and NHE3 are predominantly epithelial isoforms of the exchanger that are expressed in the apical membranes of intestinal cells

31
Q

These 2 transport mechanisms mediate electroneutral NaCl uptake in colonocytes and small intestinal cells

A

Cl−/HCO3− exchange and Na+/H+ exchange (NHE3) in the apical membrane (both electroneutral)

  • *Na goes in; H goes out
  • *Cl goes in; HCO3 goes out
  • *net formation of NaCl from the 2 transporters
32
Q

Plays a key role in intestinal Cl− absorption and HCO3− secretion as mutations in this transporter are responsible for congenital chloride diarrhea

A

Down-regulated in adenoma (DRA)

33
Q

cAMP-activated channel in the apical membrane known to participate in hormone-stimulated Cl− secretion is encoded by ____

A

Cystic fibrosis transmembrane conductance regulator gene (CFTR)

    • nonrectifying or linear (it conducts ions with equal efficiency in either an inward or an outward direction)
    • The CFTR protein is also able to mediate the conductance of other ions (notably HCO3−)
34
Q

Potassium channels in the apical membrane of epithelial cells are involved in ______, and K+ channels in the basolateral membrane are involved in ______

A

K+ secretion and Cl− secretion

35
Q

The small intestine performs what kind of electrolyte absorption?

A

electroneutral NaCl absorption and Na+-coupled nutrient absorption

36
Q

The large intestine avidly absorbs Na+ through what mechanisms? (2)

A

electrogenic mechanism involving apical Na+ channels and an electroneutral NaCl absorptive mechanism similar to that in the small intestine

37
Q

Responsible for SCFA absorption and some K+ absorption, and it is essential for conservation of fluid and electrolytes

A

The colon

38
Q

True or false
In the electroneutral absorption of NaCl by the intestine,
Na+ absorption requires the presence of Cl and vice versa

A

True

**This describes the model of electroneutral NaCL absorption wherein the mechanism is Na+/Cl- cotransport

39
Q

This mechanism of Na absorption accounts for about half of the Na+ reabsorbed in the distal colon

A

Electrogenic amiloride-sensitive Na+ absorption (ENaC)

40
Q

In the electroneutral absorption of NaCl, what kind of Na+/H+ exchanger is expressed in the apical cells?

A

NHE 2 or NHE 3

41
Q

In the electroneutral absorption of NaCl, what kind of Cl/HCO3 exchanger is expressed in the apical cells?

A

Down-regulated Adenoma (DRA)

42
Q

A mineralocorticoid well known for its Na+-retaining and K+-wasting effects on the distal nephron

A

Aldosterone

**also exerts profound effects in the distal colon

43
Q

A crypt cell function which involves an apical K+ conductance

A

K+ secretion

44
Q

In electrogenic absorption of Na in the colon, it is a compensatory mechanism to the charge imbalance as a result of Na+,K+,-ATPase pump in the basolateral membrane

A

electrogenic efflux of K+ through K+ channels in the basolateral membrane

45
Q

Aside from the compensatory mechanism of K channels in the basolateral membrane, this is another mechanism which restores electroneutrality between lumenal and serosal compartments

A

Paracellular flux of Cl from lumen into the serosal compartments

46
Q

This is where bile absorption takes place

A

Terminal ileum

47
Q

In the small intestine, the absorption of many nutrients is mediated by what type of transport mechanism?

A

Na+-coupled cotransport

  • *occurs at villus cells
  • *example: Na/glucose cotransporter
48
Q

Efflux of solute down its steep concentration gradient across the basolateral membrane is efficiently mediated by ______

A

Facilitated diffusion carriers (GLUT2)

49
Q

SCFAs are produced in the colon by bacterial catabolism of unabsorbed carbohydrate and protein. What are the predominant lumenal SCFAs in the colon?

A

Acetate, propionate, and butyrate

**Energy source for colonic epithelial cells

50
Q

Condition that activates Na+/H+ exchangers

A

Intracellular acidification and lumenal alkalinization

51
Q

about 85% of ingested Kis absorbed in this region of the intestine, with passive absorption driven by prevailing electrochemical gradients being sufficient to explain this uptake

A

Small intestine

52
Q

Active electroneutral Kabsorption occurs in this region of the intestine

A

Distal colon

53
Q

Mechanism involve in electroneutral uptake of Kfrom the lumen in the distal colon

A

Apical H, K-ATPase

54
Q

An apical H, K-ATPase promotes uptake of Kfrom the lumen to the cell. Once inside the cell, K+ exits the cell through what transport mechanism?

A

K+/Cl− cotransporter (KCC1) in the basolateral membrane

55
Q

This mechanism provides a source of intracellular Cl− to drive the basolateral K+/Cl− cotransporter

A

Cl−/HCO3 − exchange

56
Q

Produces profound Cl−-rich, acidic diarrhea commencing at birth, resulting in systemic hypochloremic, hypokalemic acidosis with volume depletion

A

Congenital chloride diarrhea

57
Q

Gene that is responsible for congenital chloride diarrhea

A

Down-regulated adenoma (DRA)

58
Q

It is caused by mutations in the amiloride-sensitive Nachannel that is present in both distal colonic and renal epithelia

A

Liddle syndrome

** autosomal dominant disorder leading to salt-sensitive hypertension

59
Q

This condition removes the inhibitory influence on the amiloride-sensitive Nachannel thus there is an increase in electrogenic Na+ absorption

A

Cystic Fibrosis

** An activated CFTR Cl− channel is required to mediate the inhibitory regulation

60
Q

True or false

Electrogenic Cl− secretion is found in stomach to proximal part of intestine

A

False – Electrogenic Cl− secretion is found in all segments of the gastrointestinal tract from the duodenum to the distal colon
** reflecting the common need for a mechanism to maintain hydration of the lumenal contents

61
Q

In Cl- secretion, what mechanism is involved in the uptake of Cl- from the blood?

A

Electroneutral Na+/K+/2Cl− cotransporter (NKCC1) in the BASOLATERAL MEMBRANE

  • *Cl− will exit the cell across the APICAL MEMBRANE when Cl− channels are opened (CFTR)
  • *Na+,K+-ATPase provides energy for this overall mechanism and recycles Na+ across the basolateral membrane.
  • *K+ channels in the basolateral membrane allow for K+ recycling, maintain cellular electroneutrality by compensating for Cl− efflux, and keep the cell hyperpolarized so that Cl− efflux across the apical membrane can be sustained
62
Q

True or false
In Cl- secretion, Nafollows passively by paracellular flux through tight junctions from the lumen to the cell compartments

A

False – From cell compartments to the lumen

** To maintain electroneutrality

63
Q

In HCO3- secretion in the duodenum, secreted HCO3− anions can be provided by carbonic anhydrase (there are two ways HCO3 is provided), which hydrates CO2 to produce intracellular HCO3− and a proton. The proton is eliminated from the cell by what mechanisms (2)?

A
  1. Basolateral Na+/H+ exchanger (NHE1) – from the cell to the bloodstream
  2. Apical Na+/H+ exchanger (NHE2/NHE3) – from the cell to the lumen
64
Q

In HCO3- secretion in the duodenum, HCO3− can be derived from the bloodstream (there are two ways HCO3 is provided) by what mechanism?

A

Basolateral Na+/HCO3− cotransporter NBC

65
Q

In HCO3- secretion in the duodenum, what are the two mechanisms in which HCO3 exits the cells?

A
  1. Cl- together with HCO3 is secreted by CFTR into the lumen (electrogenic)
  2. The Cl- secreted by the CFTR establishes a concentration gradient that drives the action of down-regulated adenoma, secreting HCO3 in exchange for Cl (electroneutral)
66
Q

True or false

Only the transverse colon up to the proximal part of descending colon can perform active K+ secretion

A

False – All portions of the mammalian colon

67
Q

K+ secretion is enhanced by what kind of diet?

A

Low-sodium diet – increased plasma level of aldosterone

68
Q

K+ secretion in the colon.

K+ uptake at the basolateral membrane is mediated by either ______ or _____, depending on the species and intestinal segment.

A

Na+,K+-ATPase or Na+/K+/2Cl−cotransport

69
Q

K+ secretion in the colon

K+ efflux at the apical membrane is through _____

A

K+ channels

Biochemistry (books and trans) (6 decks)

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