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physiology 2 > GIT physiology 4 > Flashcards

GIT physiology 4 Flashcards

1
Q

paracellular absorption

A

movement of solute is passive and the permeability is inverse to resistance and is dependant on the structure of tight junctions

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2
Q

transcellular absorption

A

movement of solute across two cell membranes (apical and basal) so will often have contrasting concentration gradients

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3
Q

transcellular absorption is driven cy

A

2 degree active transport

drives passive transport by setting up an electrochemical gradient

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4
Q

paracellular through tight junctions

A

TJs occlude paracellular passage of water and solutes

‘tightness’ varies and determined whether/how much paracellular route is used

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5
Q

colon TJs

A

tight

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6
Q

small intestine TJs

A

leaky

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7
Q

carbohydrates that are absorbed

A

only monosaccharides

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8
Q

monosaccharides

A

fructose
galactose
glucose

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9
Q

starch is made up of

A

glucose

broken down by saliva and pancreatic juices into subunits maltoses

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10
Q

maltoses are brown down by

A

maltase and a-dextinase

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11
Q

maltoses brown down into

A

glucose

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12
Q

lactose broken down into

A

galactose

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13
Q

lactose broken down by

A

lactase

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14
Q

lactose broken down in

A

the intestine

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15
Q

sucrose broken down to

A

fructose

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16
Q

sucrose broken down by

A

sucrase

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17
Q

sucrase

A

break sucrose down into fructose

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18
Q

lactase

A

breaks lactose down into galactose

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19
Q

maltase and a-dextrinase

A

breaks maltose down into glucose

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20
Q

GLUT5

A

transports fructose

depends on driving gradient of fructose

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21
Q

SGLT1

A

sodium dependant transport of glucose/galactose

able to scavenge

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22
Q

GLUT2

A

allows glucose and galactose to diffuse out if there is enough in the cell

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23
Q

disaccharides

A

broken down into monosaccharides

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24
Q

lactase deficiency

A

causes lactose to go straight through the digestive system without being absorbed unchanged

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25
consequence of not absorbing lactose
osmotically active creates osmotic drag and water will follow bacteria anaerobically metabolise lactose creating gas gas and water overpresent in stool
26
protein digestion
pepsin digests some proteins pancreatic proteases convert most luminal orcein to oligopeptides and amino acids peptidases liberate free amino acids
27
apical AA transporters
present on apical membrane - distinct transporters for differently charged AAs - Na co-transport - scavenger transporter
28
basal AA transporters
Na-independent
29
pepT1
peptide transporter | requires a proton gradient
30
3 classes of lipids
- triglycerides - phospholipids - cholesterol
31
triglycerides
glycerol with 3 fatty acids storage and transformation form of energy fast deposits for insulation and protection
32
phospholipids
lecithins, cephalins, sphingomyelins glycerol and 2 fatty acids phosphorous group
33
cholesterol
``` synthesised from acetyl-CoA structural role in membranes precursor for - bile salts - steroid hormones - vitamin D ```
34
digestion of triglycerides
lingual lipase and gastric lipase (less important) mainly pancreatic lipase gives 2 fatty acids and monoglyceride
35
fat absorption
can diffuse through bilayer also cavoelae-mediated uptake and carrier-mediated transport eg. fatty acid translocase packed into lipoprotein complexes that carry lipids from small intestine through circulation - chylomicrons - exocytosed into lacteals (SI lymphatic vessels), then secreted into bloodstream
36
water is mostly absorbed in
small intestine
37
water is absorbed by
osmotic gradient
38
electrolytes and minerals
active or passive (requires electrochemical gradient) | used to set up the osmotic gradient required to move water across membranes
39
Chloride is absorbed via
passive diffusion and Na, H, Cl, HCO3 exchange
40
chloride is secreted via
Cl- channels | -CTFR
41
-CFTR
cystic fibrosis transmembrane conductive regulator | regulated by cell volume or signalling
42
CFTR gating
CL- diffuses out down its concentration gradient | water follows
43
CTFR is regulated by
cAMP | when cAMP goes up chloride goes out
44
bioavailability of minerals depends on
pH redox state of the metal dietary complexes with enhance and diminish solubility
45
dietary complexes which enhance solubility
organic acids - ascorbate (fruit juice), lactate (fermented milk), pyruvate/cysteine/histidine
46
dietary complexes which diminish absorption
phytates (in cereals), tannins (in tea), oxalates (rhubarb, greens), carbonates (Perth)
47
daily calcium absorption
1g of Ca ingested mostly most bioavailable absorbed transcellularly or paracellularly leaky tight junctions allow calcium to pass through TRPV6 calcium pump calbindin binds systolic Ca2+ - prevents pree Ca2+ from blocking TRPV6
48
TRPM6
transports magnesium
49
dietary iron is eaten in 2 forms
haem iron | non-haem iron
50
haem iron
iron in meat, blood, muscle bound to haem more readily absorbed taken up as Fe-porphyrin complex by haem transporter HT
51
non-haem iron
iron in vegetables either ferrous or ferric ferric iron is completely insoluble divalent metal transporter (DMT)
52
ferric iron
completely insoluble and must be reduced first
53
DMT
divalent metal transporter can only pick up ferrous iron ferric iron must first be reduced but this is not an efficient process and most will be lost
54
iron inside the cell
very reactive | needs to be bound to ferritin for storage
55
basal iron transporter
IREG1 - ferroportin
56
iron the the blood
bound to transferrin for transport
57
Haem-Fe transporter
more efficient | enzyme used to break it apart
58
if cells with iron die
iron is lost from the system | hepcidin regulates plasma iron levels
59
when there is too much iron in the system
hepcidin is secreted hepcidin switches off all ferroportin channels (IREG1) iron enters cells but is all stored as ferritin which is toxic to the cell so the cell dies and the iron is lost to the system
60
hepcidin
regulates plasma iron levels | secreted from the liver
61
when ferroportin is switched off by hepcidin
iron is still take up by the cell and stored as ferritin too much ferritin is toxic to the cell cell dies and iron is lost

physiology 2 (21 decks)

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