Brainscape's Knowledge GenomeTM

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


See full index

BRS > Ions, vitamins and minerals > Flashcards

Ions, vitamins and minerals Flashcards

1
Q

What molecules can cross the cell membrane more easily than water soluble molecules (polar)?

A

Lipid soluble (non polar).

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

In terms of tonicity, how does water move in osmosis?

A

From hypotonic (low concentration of solutes) to hypertonic (high concentration of solutes).

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

What is paracellular transport?

A

Transport of molecules through tight junctions and lateral intercellular spaces.

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

What is transcellular transport?

A

Transport of molecules through epithelial cells.

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

Processes in which solutes cross cell membranes?

A

Simple diffusion. Facilitated diffusion. Active transport.

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

Two types of transport proteins?

A

Channel proteins and carrier proteins.

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

How do channel proteins transport solutes?

A

Form aqueous pores allowing specific solutes to pass across membrane.

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

How do carrier proteins transports solutes?

A

Bind to the solute and undergo a conformational change to transport it across the membrane.

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

How are channel proteins different to carrier proteins?

A

Channel proteins transport solute faster than carrier proteins. Carrier proteins have a solute binding site while channel proteins have selective filter in aqueous pore.

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

How do mechanically-gated ion channels work?

A

Tension, compression, swelling, and shear stress can alter the conformation of the protein, opening a transmembrane channel that allows the passage of ions

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

3 types of carrier channel proteins?

A

Uniporter, symporter and antiporter.

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

What is primary active transport?

A

Movement of solutes against concentration gradient by using ATP.

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

What is secondary active transport?

A

Movement of solute against concentration gradient which is driven by another solute moving down an electrochemical gradient.

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

Key points about facilitated diffusion?

A

Increases the rate at which a substance can flow down its concentration gradient. Requires a channel or carrier protein. Does not require energy.

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

Why can fructose be transported via facilitated diffusion instead of active transport?

A

Low levels of fructose in enterocyte and plasma. Fructose can diffuse across basolateral membrane of enterocyte down a concentration gradient.

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

GLUT2 key points?

A

High capacity, low affinity facilitative transporter.

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

How is water absorbed in the GI tract?

A

Osmotic flow of water through tight junctions into intercellular space due to hypertonic solution present in intercellular space (high concentration of ions).

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

Where is the greatest amount of water absorbed?

A

Jejunum (small intestine).

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

What is the main ion that drives water absorption? How does it happen?

A

Na+ is transported from lumen into enterocytes.

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

How is sodium absorbed in the duodenum?

A

Counter transport in exchange of H+ ions.

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

How is sodium absorbed in the jejenum?

A

Co-transport with amino acids and monosaccharides.

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

How is sodium absorbed in the ileum?

A

Secondary active transport. Co-transport with chloride ions.

23
Q

How is sodium absorbed in colon?

A

Restricted movement through ion channels.

24
Q

How is chloride absorbed in the colon?

A

Secondary active transport. Exchanged with bicarbonate.

25
Q

How is potassium absorbed in the small intestine?

A

Diffusion via paracellular junctions.

26
Q

How is sodium in enterocytes transported into the lateral intercellular spaces?

A

Active transport by Na+K+ATPase in lateral plasma membrane.

27
Q

How is chloride and bicarbonate in enterocytes transported into lateral intercellular spaces?

A

Diffusion due to electrical potential gradient caused by sodium in lateral intercellular space.

28
Q

Where is calcium absorbed?

A

Duodenum and ileum.

29
Q

When is calcium absorption increased?

A

If someone follows a low calcium diet.

30
Q

How is calcium absorbed into the blood?

A

Via ion channels in paracellular junctions. Via enterocytes.

31
Q

Explain calcium absorption via enterocytes

A

Calcium enters enterocyte via TRPV6. To prevent calcium intracellular signalling effects, calbindin binds to calcium to inactivate it. Calcium is then excreted on basolateral side via PMCA or sodium calcium exchange transporter.

32
Q

How does calcitriol upregulate calcium absorption in enterocytes?

A

Alters gene expression and increases transcription of TRPV6 and PMCA. Allowing more calcium to be absorbed into the enterocytes and excreted into the blood. It also increases levels of calbindin.

33
Q

Key points about PMCA transporter?

A

Plasma membrane Ca2+ATPase. Has high affinity but low capacity for calcium.

34
Q

Why is the PMCA transporter important?

A

Maintains low intracellular calcium as pumps calcium across basolateral membrane against concentration gradient using ATP. Important as high intracellular calcium can cause unwanted signalling effects within the cell.

35
Q

Key points about sodium calcium exchanger?

A

Low affinity for calcium but high capacity. Pumps calcium against concentration gradient across basolateral membrane.

36
Q

What is the best absorbed form of iron?

A

Heme iron.

37
Q

What transporter allows for absorption of heme iron?

A

Heme carrier protein 1.

38
Q

What transporter allows for absorption of non heme iron?

A

DMT1 (Divalent metal transporter 1)

39
Q

Why is ferritin binding to intracellular iron important?

A

Prevents iron from promoting oxidative stress.

40
Q

What happens to iron that binds to ferritin?

A

Irreversibly bound to ferritin (can’t be unbound). Oxidised to ferric form. Stores iron which is eventually lost by shedding of enterocytes into faeces.

41
Q

What converts ferric iron to ferrous iron so it can be absorbed by DMT1?

A

Duodenal cytochrome B.

42
Q

Explain iron absorption

A

Heme iron enters via HCP1 and non heme iron is reduced by duodenal cytochrome B and enters cells via DMT1. Most iron binds to ferritin and excreted into faeces. Some of the iron moves across basolateral side into blood via ferroportin 1 and subsequently oxidized to ferric form by hephaestin and transferred to the carrier protein apotransferrin and travels as transferrin in blood.

43
Q

What vitamin helps with absorption of non heme iron?

A

Vitamin C (acts as a reducing agent).

44
Q

Two ways in which heme iron is absorbed?

A

Via HCP1 and receptor mediated endocytosis.

45
Q

What does hepcidin act on to regulate iron absorption?

A

Suppresses ferroportin function. Less iron absorbed into blood.

46
Q

What increases ferritin synthesis?

A

Increase iron concentration in cytosol.

47
Q

How are most vitamins absorbed?

A

Diffusion.

48
Q

Where is vitamin B12 stored?

A

Liver.

49
Q

Why is haptocorrin important for B12 absorption?

A

B12 is easily denatured by HCL in the stomach. Haptocorrin prevents this by binding to B12.

50
Q

Where is haptocorrin released from?

A

From salivary glands and stomach.

51
Q

Explain B12 absorption

A

Haptocorrin binds to B12. Parietal cells in stomach secrete intrinsic factor which binds to B12. B12 intrisic factor complex binds to cubilin receptor and taken up in distal ileum. B12 intrinsic factor complex broken down in enterocyte and b12 binds to transcobalamin II (TCII) where it then crosses basolateral membrane into blood. Taken to liver where TCII is broken down.

52
Q

What transports b12 in the blood once it leaves enterocytes in distal ileum?

A

Transcobalamin II.

53
Q

What oxidises iron before it is transported into the blood?

A

Hephaestin.

BRS (52 decks)

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