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Bioregulatory systems 4 > Ions vitamins and minerals > Flashcards

Ions vitamins and minerals Flashcards

1
Q

What are the main concentrations used?

A
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2
Q

How does diffusion differ over microscopic vs macroscopic distances?

A

Rapidly over microscopic distances and slowly over macrocytic distances

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3
Q

What does hypotonic and hypertonic mean?

A

Hypotonic-areas with lots of water and low sodium/solutes

Hypertonic-areas with less water and more solutes/sodium

Water moves via osmosis from Hypotoni to Hypertonic regions

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4
Q

How can molecules pass across the epithelium ot enter the bloodstream?

A

PARACELLULAR TRANSPORT- through TIGHT JUNCTIONS and lateral intercellular spaces

TRANSCELLULAR TRANSPORT-through the epithelial cells

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5
Q

By which 3 methods do solutes cross cell membranes ?

What are the 2 types of transport proteins involved?

A

Methods:

  • Simple diffusion
  • Facilitated diffusion
  • Active Transport

Transport Proteins:

  • Channel proteins from aqueous pores to allow solutes to pass through the membrane
  • Carrier proteins bind ton solute and underon conformational change to transport it across the membrane

Channel proteins allow much faster transport than carrier proteins

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6
Q

What are the different types of channel protein

A

VOLTAGE GATED-change in voltage of the membrane opens/closes it

LIGAND GATED EXTACELLULAR- ligand bind the channel outside the cell causing it to open/close

LIGAND GATED INTRACELLULAR-ligand bind to the channel inside the cell causing it to open/close

MECHANICALLY GATED- physical distortion of the cell membrane causes it to open e.g touch

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7
Q

What are the 3 types of carrier proteins?

A

UNIPORT- solute comes in and goes out formt he other side in a simple way

SYMPORT-coupled transporter, both ions that enter go in the samne direction

ANTIPORT- coupled transporter where the 2 ions go in opposite directions through it as they are exchanged

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8
Q
A
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8
Q

What are the 2 types of active transport?

A

PRIMARY- uses energy derived form ATP

SECONDARY derives energy from the concentration gradient of another molecule that is actively transported

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9
Q

What are examples of primary active transporters, seconday active tranporters and facilitaed diffusion transporters?

A

Primary-Na+/K+ ATPase (PANCREATIC HC03- secretion)

Secondary -HCO3-/Cl- transporter(Pancreatic HCO3- secretion)

Facillitated diffusion-GLUT-2 and GLUT-5(small bowel absorption of monosaccharides)

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10
Q

How are glucose and galactose absorped into blood ?

A
  • SECONDARY active transport - CARRIER PROTEINS on APICAL border called SGLT-1 which transport glucose against concentration gradient from the lumen into the cell
  • Glucose exits cell at BASOLATERAL MEMBRANE via carrier portein GLUT 2
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11
Q

How is fructose absorped (into enterocytes and then blood stream)?

A

FACILITATED DIFFUSION- by carrier protein GLUT-5 on apical membrane

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12
Q

How does

A
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13
Q

What are 5 features of water absorption in the GI tract?

A
  • 99% of water presented here is absorbed
  • Water absorption powered by ions
  • The greatest amount of water is absorped in the smal intestine especilly the JEJUNUM
  • 8L absorbed bny the small bowlel
  • 1.4 L absorbed in the Large Bowel
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14
Q

What are sources of the water that you absorb in the GI Tract?

A

2L-ingest

2L-Gastric/stomach juice

  1. 2L Saliva
  2. 7L -Bile
  3. 2L pancreas
  4. 4L-intestinal
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15
Q

How is Sodium transported into enterocytes at different stages of the gut?

A

PROXIMAL BOWEL-counter tansport in exchange for H+

JEJUNDUM-cotransport with amino acids and monosaccharides

ILIEUM-Co-Transport with Cl-

COLON-restricted movement through ion channels

Transport becomes more efficient as you travel down the intestine

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16
Q

How is Cl- transported into enterocytes in different parts of the GI tract?

A

ILIEUM- cotransported with Na+

COLON-exchanged woith HCO3-

both are secondary active transport

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17
Q

How does K+ enter enterocytes?

A

-DIFFUSES via PARACELLULAR PATHWAYS in small intestine, leaks out between cells in the colon

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18
Q

What happens to Na+ once it enters enterocytes?

A

-Actively transported into laterall intercellular spaces(spaces inbetween neighbouring cells) via Na+K+ATPase

19
Q

Where does water travel to from the gut lumen and how?

What does this cause?

A
  • Intracellular space as theres lots of sodium here making it HYPERTONIC so water can move here via osmosis
  • via adjacent cells adn TIGHT JUNCTIONS
  • This causes an increased HYDROSTATIC PRESSURE in the intracellular space, allowing the ions and water to move across the basement membrane into the cappiilaries
20
Q

Where does the absoption of calcium occur?

A

DUODENUM and ILIUEM

21
Q

What are the 2 ways that calcium is absorped from the lumen?

A
  • Directly via paracellular ION CHANNELS
  • IMcal facilitated diffusion transporters
22
Q

Describe calium absorption through enterocytes?

A

1) enters by facilitated diffusion
2) binds to CALBINDIN in the cell
3) this allows it to be transported out of the cell via PMCA(Ca2+ ATPase) against conc gradient OR via exchange with Na+ via NCX

23
Q

What is the importance of Vitamin D in calcium absorption?

A
  • Increases the aborsoption of calcium via paracellular absorption
  • Increases the transcription of channels that allow the absorption of calcium form the lumen, and channels that allow calcium ot pass out of the cell and into the capillaries (Ca2+ ATPase/PDMA)
  • Increase Levels of CALBINDIN
24
Q

Why does calcium bind to Calbindin when it enters the cell?

A
  • to prevent it causing an action potential /intracellular signal
  • also calcium only enters the cell in low concentrations to prevent this too
25
Q
A
26
Q

What are the features of the 2 transporters that transport calcium across the basolateral membrane out of the cell?

A

Na+/Ca+ transporter-low affinity for calcium but high capacity. Requires larger concentrations of calcium to be effective

PMCA-high affinty for calcium but low capacity . Helps maintain the low conc of calium normally within the cell

27
Q

What does deffiecincy off Vitamin D cause in adults and children?

A

Kids- Rickets

Adults-Osteoporosis

28
Q

What are the key feature of iron?

A
  • can act as a electron donar and acceptor
  • can be toxic in excess but we have non mechanism to secrete it
29
Q

How much iron do we ingest vs absorb?

A

Ingest- 15-20mg per day

Absorb- 0.5-1.5mg per day

30
Q

How is iron present in the body?

A

Inorganic Ion- Fe3+(Ferric), Fe2+(Ferrous)

-As part of HAEM group e.g. in haemoglobin and myoglobin

31
Q

How absorpable is each type of Iron?

A

Fe2+-absorped

Fe3+- cannot be absorbed so is reduced to Fe2+ by Vitamin C

Haem-more readily absorbed(20% vs 5% as they have there own channels)

32
Q

How is dietry Haem absorbed into enterocytes?

A

via HAEM CARRIER PROTEIN 1(HCP-1) and receptor mediated endocytosis

33
Q

How is iron absorped from the duodenum?

A

1) DUODENAL CYTOCHROME B(Dcytb) catalyses the reduction of Fe3+ to Fe2+
2) Fe2+ transported into enterocytes via DIVALENT METAL TRANSPORTER 1 (DMT-1), a H+ coupled Co-receptor
3) Fe2+ binds to unknown factors and is carried to the basolateral membrane where moves through FERROPORTIN ION CHANNEL out of the cell
4) HEPHAESTIN (transmembrane copper dependent ferroxidase) that converts Fe2+ into Fe3+
5) Fe3+ binds to APOTRANSFERIN and travels in the blood as Transferin

34
Q
A
35
Q

What is the role of Hepcidin?

A

Major iron regulating protein that supresses FERROPORTIN funtion to decrease iron absorption

36
Q

How is iron stored?

A

1) Ferrous Iron(Fe2+) binds to APOFERRITIN in the cytosol and is oxidised to Fe3+ which crystalises in the shell
2) This forms FERRITIN micelles
3) A singel FERRITIN moleule can store up to 4000 iron ions

37
Q

Why is iron stored?

A

to prevent too much absorption as this can be toxic

38
Q

What are the features of ferritin?

A
  • Binding of iron to ferritin is irreversible
  • Ferritin is not available for transport into the plasma
  • Ferritin is lost in the intestinal lumen and excreted in faeces
  • increase in iron in cytosol of cells =increase in ferritin synthesis

ferritin=blood protein that contains iron

39
Q

How vitamins usually transported?

A

Passive diffusion

-except K is taken up via active transport

40
Q

Which are the fat soluble vitamins

A

-A, D, E, K

41
Q

Where is B12 stroed and how much?

A

Liver- 2-5mg

42
Q

What does impaired absorption of vitamin B12 cause?

A

retards maturation of Red Blood Cells causing PERNICIOUS ANAEMIA

43
Q

How is B12 absorped into bloodstream?

A

1) dietry B12 is attatched to dietry proteins and ingested intot he stomach
2) in the stomach the acid causes the B12 and proteins to become detatched
3) B12 attatches to protein HAPTOCORRIN (r-protein)- this prevents the stomach acid destroying B12 and allows its safe passage throught the Duodenum
4) Once it gets to the end of the duodenum the Haptocorrin denatures itself.
5) B12 reaches the TERMINAL ILIEUM and attatches to intrinsic factors (secreted in the stomach by parietal cells)
6) B12 can now be absorped in ONLY the DISTAL ILIEUM as here the cells have a specific channel (CUBULIN RECEPTOR) that allows the absorption of the B12-intrinsic factor complex
7) In the enterocytes B12 detatches from the intrinsic factors
8) It exits the cell by crossing the Basolateral membrane via the MDR1 channel to enter the capillaries
9) Capillaries have TRANSCOBALAMIN (made in enterocytes) which B12 attatches to(carries B12)

44
Q

What happens to B12 once it binds to Trancobalamin II in the bloodstream?

A

1) travels to liver
2) liver has TCII receptors that allow the uptake of the complex
3) Proteolysis then breaks down TC inside the cell

45
Q

Where is Haptocorrin released from?

A

saliva and Parietal cells in the stomach

46
Q
A

Bioregulatory systems 4 (11 decks)

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