Brainscape's Knowledge GenomeTM

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


See full index

Physiology 3003 > Lecture 9--absorption of water minerals & vitamins > Flashcards

Lecture 9--absorption of water minerals & vitamins Flashcards

1
Q

H2O transport is a ______ process

A

Passive process

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

Aquaporins

A

Specialised H2O channels, determine TRANSCELLULAR H2O permeability

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

________ gradients drive H2O transport

A

OSMOTIC gradients drive H2O transport

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

Describe TRANSCELLULAR absorption

A

Transcellular absorption = movement ACROSS cells (between the APICAL and BASAL membrane)

Involves passive AND active transport …
…active transport required on AT LEAST 1 surface (i.e. passive diffusion INTO (out of) the cell and active transport OUT OF (in to) the cell)

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

Is transcellular absoprtion an active or passive process?

A

BOTH

At least 1 surface (apical or basal) must have active transport, while the other surface can have passive diffusion

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

Describe PARACELLULAR absorption?

A

PASSIVE movement BETWEEN ADJACENT CELLS through TIGHT JUNCTIONS

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

What regulates paracellular absorption?

A

Permeability is regulated by structure of TIGHT JUNCTIONS (‘tightness’ v ‘leakiness’)

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

Is paracellular absorption passive or active?

A

paracellular absorption = PASSIVE PROCESS

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

Is electrolyte transport passive or active process?

A

Can be EITHER (passive or active)

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

Give a brief overview of the active transport mechanism(s) for ELECTROLYTE TRANSPORT

A

electrolytes can be transported actively or passively.

Active transport: derives energy from the hydrolysis of ATP. Moves solute against electrochemical gradient

Can be DIRECT ACTIVE TRANSPORT (e.g. N-ATPase pump)
or
INDIRECT ACTIVE TRANSPORT: in which active transport on one surface drives passive transport on other surface by establishing electrochemical gradient.

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

What is meant by INDIRECT ACTIVE TRANSPORT?

A

in which active transport on one surface drives passive transport on other surface by establishing electrochemical gradient.

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

Briefly outline PASSIVE TRANSPORT + the sub-classifications

A

Passive transport DOES NOT REQUIRE ATP
Moves solutes WITH electrochemical gradient

  • FACILITATED DIFFUSION (carrier protein, specific to a certain molecule/class of molecules)
  • PASSIVE DIFFUSION (pore, nonspecific)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is FACILITATED DIFFUSION

A

Involves CARRIER PROTEINS, specific to a certain molecule or class of molecules

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

What is PASSIVE DIFFUSION

A

Involves a PORE that is non-specific

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

Outline the role of TIGHT JUNCTIONS in regulating water absorption (examples of this regulation?)

A

TJs OCCLUDE PARACELLULAR PASSAGE OF H2O & SOLUTES (the ‘tightness’ of TJs can vary)

The COLON has TIGHT TJs
The SMALL INTESTINE has LEAKY TJs (which allows things to pass in)

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

Outline the role of AQUAPORINS in regulating H2O absorption?

A

Aquaporins= specialised H2O channels (charge specific, size specific, tetrameric protein)

–UP-REGULATING EXPRESSION of APs on membranes = INCREASES PERMEABILITY

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

What is the importance of electrolytes in water absorption?

A

Electrolytes are moved across the membrane to establish osmotic gradient down which H2O will travel

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

What process powers Na+ transport into cell?

A

Electrochemical gradient established by Na/K pump

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

What are the (4) ways of SODIUM entering cells?

A

(1) PASSIVE DIFFUSION (Na+ channels)
(2) CO-TRANSPORT (Na/AA or Na/Glucose co-transporters)
(3) EXCHANGER (Na+/H+ exchanger…Na+ IN, Proton(H+) OUT)
(4) PARALLEL Na/H & Cl/HCO3 EXCHANGE

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

Outline how CO-TRANSPORTERS operate in Na+ absorption by cells

A

2 types of transporter: Na+/Glucose & Na+/amino acid

Location: the JEJUNUM (but also ileum)

Requirements:
=> Low intracellular [Na+] (=Na/K transporter)
=> Low intracellular [Glucose] (=glucose channels on basal membrane)
=> Low intracellular [Amino Acids] (=AA channels on basal membrane)

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

Outline how EXCHANGERS operate in Na+ absorption

A

Na+/PROTON (Na/H+) exchanger = brings 1 Na+ in, x1 H+ out)

Location: DUODENUM & JEJUNUM

Requirements:

(1) Low intracellular [Na+] (=Na/K transporter)
(2) Low intracellular [H+] (=Na+/H+ exchanger on basal surface removes 1H+ and brings in 1 Na+)

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

Outline how PARALLEL EXCHANGE operates in Na+ (and Cl-) absorption

Where does parallel exchange take place?

A

Involving products of reaction of: CO2 + H2O + Carbonic anhydrase ==releases==> H+ ion (used in Na/H exchanger on apical surface) and a HCO3- (hydrogen carbonate) (used in CL-/HCO3- exchanger on apical surface)

Takes place in the PROXIMAL COLON and the ILEUM

23
Q

What energetically drives Parallel exchange of Na/H & Cl/HCO3-?

A

HYDROLYSIS OF H2O

24
Q

What are the requirements for Parallel Na/H & Cl/HCO3- exchange

A

(1) Low intracellular [Na+]
(2) Low intracellular [Cl-]
(3) Hydrolysis of H2O

25
Q

Outline the different mechanisms for Na+ absorption in the different regions of the GIT

  • Jejunum
  • Ileum
  • Duodenum
  • Proximal Colon
  • Distal colon
A
  • Jejunum: (1) Na/Gluc & Na/AA COTRANSPORT (2) Na/H EXCHANGER
  • Ileum: (1) Na/Gluc & Na/AA COTRANSPORT (a little) (2) PARALLEL Na/H & Cl/HCO3- EXCHANGE
  • Duodenum: (1) Na/H EXCHANGER
  • Proximal Colon: (1) PARALLEL Na/H & Cl/HCO3- EXCHANGE
  • Distal colon: PASSIVE DIFFUSION by Na+ channels
26
Q

What are the (3) Mechanisms for CHLORIDE absorption?

A

(1) PASSIVE DIFFUSION
- Transcellular routes (Cl- channels, down ELECTROCHEMICAL gradient)
- Paracellular route (SOLVENT DRAG sucks Cl- through pores in tight junctions)

(Ileum=low absorb….Jejunum/Distal colon = high absorp)

(2) Cl-HCO3- exchange (ileum/proximal colon=moderate absorp)
(3) Parallel Na/H & Cl/HCO3- exchange(ileum/distal colon=moderate absorp….proximal colon = high absorb)

27
Q

How is Cl- secreted in the GIT?

A

by Cl- CHANNELS
= GATED
—>Ca2+ gated
—>Volume gated (stretch; expand cell = let Cl- out to reduce volume)
—>Ligand-gated anion
—>CFTR (cystic fibrosis transmembrane conductance regulator)

=PASSIVE (mostly closed)

28
Q

What mutation causes Cystic fibrosis? (and how)

A

Mutation in the CFTR Cl- channel (CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR)

  • a transcellulra signalling cascade involving cAMP triggers opening of CFTR channel
  • cAMP –> activate protein kinase A –> phosphorylates R-domain of CFTR –> conformational change = open
  • Anything that up-regulates cAMP will cause CFTR to be open –> Cl- secreted –> creates SOLVENT DRAG –> H2O leaves cell –> DEHYDRATION
29
Q

What is a SECRETAGOGUE?

A

anything that perturbs cAMP signalling is a SECRETAGOGUE for Cl- ions (.: anything that increases cAMP)

30
Q

Where does Cl- secretion take place in the GIT?

A

Moderate secretion….

(1) Duodenum
(2) Jejunum
(3) Ileum
(4) Proximal colon
(5) Distal colon

31
Q

What are the processes for K+ absorption?

What is special about K+ absorption?

A

(1) PASSIVE DIFFUSION (jejunum & ileum)

(2) ACTIVE K+/H+ EXCHANGER (distal colon)
- -NOTE in this case K+ absorption is an active process on BOTH the apical and basal surface (Na/K pump on basal). BECAUSE on both sides K+ is being pumped IN .: no electrochemical gradient for K+ movement into the cell is established.

32
Q

Account for the ACTIVE absorption of K+ on the apical surface of cells in the distal colon?

A

K/H+ exchange requiring ATP…in this case K+ absorption is an active process on BOTH the apical and basal surface (Na/K pump on basal). BECAUSE on both sides K+ is being pumped IN .: no electrochemical gradient for K+ movement into the cell is established.

33
Q

What method of K+ absorption occurs in different regions of the GIT?

A

(1) JEJUNUM: Passive diffusion
(2) ILEUM: Passive diffusion
(3) DISTAL COLON: ACTIVE Na/H exchange

34
Q

What methods are used for K+ SECRETION by cells in the GIT

A

(1) Passive secretion
(2) Apical K+-channel powered by basal Na/K pump

check this answer with lecture

35
Q

What factors influence BIOAVAILABILITY (Absorption) of minerals?

A

(1) COMPLEXES can either ENHANCE SOLUBILITY (aid absorption) or DIMINISH SOLUBILITY (hinder absorption)
(2) pH
(3) Redox state of metals (e.g. Fe3+ cannot be absorbed but Fe2+ can)

36
Q

What complexes aid/hinder absorption of minerals (and how)

A

Complexes that AID absorption:

  • -ASCORBATE
  • -LACTATE

Complexes that HINDER absorption:

  • -PHYTATES (in cereals)
  • -TANNATES (in tea)
  • -COMPETITION with other minerals (e.g. Ca2+ blocks Pb2+ absorption)
37
Q

Ca2+ is usually bound to ______ and cannot be absorbed

A

Ca2+ is usually bound to OXALATE and cannot be absorbed

38
Q

How much of the Ca2+ that we ingest, do we actually absorb?

A

1/2

39
Q

What are the mechanisms for Ca2+ absorption in the GIT?

A

(1) ACTIVE TRANSCELLULAR ROUTE:
–> Ca2+ enters cell by the CAT 1 CHANNEL
–> within cell Ca2+ is bound to CALBINDIN (to stop it from being active in the cell)
–> Shuttled to apical surface, exported from cell by ACTIVE TRANSPORT
=> Ca2+ ATPase or;
=> Ca2+ ATPase antiporter (exchanges Ca2+ for Mg2+ or Na+)

(2) PARACELLULAR DIFFUSION (in the small intestine)

40
Q

Explain active transcellular transport of Ca2+

A

ACTIVE TRANSCELLULAR ROUTE:
–> Ca2+ enters cell by the CAT 1 CHANNEL
–> within cell Ca2+ is bound to CALBINDIN (to stop it from being active in the cell)
–> Shuttled to apical surface, exported from cell by ACTIVE TRANSPORT
=> Ca2+ ATPase or;
=> Ca2+ ATPase antiporter (exchanges Ca2+ for Mg2+ or Na+)

41
Q

Vitamin ____ activates absorption of Ca2+ by _____

A

Vitamin D activates absorption of Ca2+ by ;

TRANSCRIPTIONAL CASCADE IN CELL THAT UP-REGULATES:
>CAT1 channels
>CALBINDIN MOLECULE

42
Q

Mg2+ absorption

–Apical surface:

–Basal surface:

A

–Apical surface: TRPM6 (transient receptor protein) (passive transport)

–Basal surface: Mg-ATPase (active transport)

43
Q

Ca2+ absorption

  • -Apical surface:
  • -within cell:
  • -Basal surface:
A

–Apical surface: CAT 1

– Within cell: CALBINDIN

–Basal surface:
==> ATPase
==> ATPase ANTIPORTER (exchange Ca2+ for Mg2+/Na+)

44
Q

The amount of Mg2+ we absorb depends on ___________

A

the amount we have in our diet

45
Q

Water soluble vitamin absorption can be dependent on what?

A

(1) Na+ DEPENDENT (vit B3/5/7, vitC)
(2) Na+ INDEPENDENT (vit B1/2/6)
(3) pH DEPENDENT (vit B1/3/6)

46
Q

How are lipid soluble vitamins absorbed?

A

in the same way as fats –by BILE SALT MICELLES

47
Q

What are the 2 categories of vitamins?

A

LIPID SOLUBLE

WATER SOLUBLE

48
Q

What could cause deficiencies in WATER SOLUBLE VITAMINS?

A

pH changes

Na+ deficiencies

49
Q

What could cause deficiencies in LIPID SOLUBLE vitamins?

A

Blocked bile ducts (=unable to emulsify fats = unable to absorb fat soluble vitamins)

50
Q

What are the water soluble vitamins?

A

B vitamins

Vitamin C

51
Q

What are the lipid soluble vitamins?

A

A,D,E,K

52
Q

How is vitamin B12 absorbed?

A

We don’t have a channel for vitB12

(1) needs to be COMPLEXED WITH INTRINSIC FACTOR (in the DUODENUM)
(2) Take up complex by RECEPTOR MEDIATED ENDOCYTOSIS (in the ILEUM)
(3) CLEAVE B12 from intrinsic factor = FREE B12
(4) Bind free B12 –> TRANS-COBALAMIN 2 (TCII)
(5) EXOCYTOSIS to blood stream

53
Q

Predominant site for H2O absorption in the GIT?

A

The SMALL INTESTINE

Physiology 3003 (15 decks)

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