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Digestion 4: Digestion & Absorption Flashcards

1
Q

what are the nutrients we get from diet?

A
  • carbs
  • fat
  • protein
  • water, electrolytes, vitamins
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2
Q

what are the nutrients absorbed by the small intestines?

A
  • monosaccharides
  • fatty acids
  • monoglycerides
  • cholesterol
  • AA
  • water, vitamins, electrolytes
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3
Q

what type of transport is endocytosis or exocytosis?

A

transcytosis

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4
Q

function of sucrase

A

sucrose → glucose + fructose

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5
Q

function of maltase

A

maltose → glucose + glucose

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6
Q

function of lactase

A

lactose → glucose + galactose

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7
Q

function of amylase

A

starch, glycogen → disaccharides

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8
Q

2 ways in which shorter peptide chains can be formed

A
  1. endopeptidase → shorter peptide chains

2. exopeptidase (aminopeptidase & carboxypeptidase) → digest peptide chains from either end to release AA

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9
Q

what is needed when peptide chains are broken?

A

H2O (hydrolysis)

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10
Q

does body make more aminopeptidase or carboxypeptidase

A

carboxypeptidase

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11
Q

function of lipase

A

triglyceride → monoglyceride + FFA

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12
Q

what are the fats that we eat? What is the main one?

A
  • triglycerides (90%)
  • phospholipids
  • cholesterol
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13
Q

how does monosaccharides get through epithelial cells in small intestines?

A

enter: facilitated diffusion & co-transport
exit: facilitated diffusion

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14
Q

how does fat get through epithelial cells in small intestines?

A

enter: diffusion
exit: exocytosis as chylomicrons

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15
Q

how does AA and short peptides get through epithelial cells in small intestines?

A

enter: facilitated diffusion & co-transport
exit: facilitated diffusion & co-transport

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16
Q

brush-border enzyme for AA?

A

dipeptidases

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17
Q

which macronutrient is not digested in the stomach?

A

lipids

carbs get some digestion from leftover salivary amylase

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18
Q

digestion of carbs at the small intestines

A
  1. pancreatic a-amylase

2. lactase, maltase, sucrase

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19
Q

digestion of proteins at the small intestines

A
  1. trypsin, chymotrypsin, elastase, carboxypeptidase

2. dipeptidase

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20
Q

digestion of fat at the small intestines

A

bile acids;

pancreatic lipase

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21
Q

function of salivary amylase

A

starch → MALTOSE + maltotriose + dextrin

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22
Q

__% of starch digestion occurs in mouth, __% occur in stomach

A

5;

35

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23
Q

about ___ min after swallowing, salivary amylase becomes inactivated by low stomach pH

A

30-40

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24
Q

function of pancreatic amylase

A

starch → MALTOSE + maltotriose + dextrin

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25
even though pancreatic amylase == salivary amylase, it is more potent because...
- food is smaller at small intestines, so there is more SA for it to act on - food stays in intestines longer
26
___ is important for pancreatic amylase activity because...
bicarb; | need to neutralize acidic chyme so pancreatic amylase is at the optimal pH
27
how to explain the symptoms of lactose intolerance?
diarrhea: lactose in large intestines draw water into lumen gas: bacteria in large intestines use lactose as food → gas is byproduct of fermentation cramps: build up of CO2 → distention → peristalsis
28
what is used to absorb monosaccharides?
GLUT-5 & SGLT (sodium glucose linked transporter)
29
brush-border enzymes used to digest saccharides
- maltase-glucoamylase - dextrinase - sucrase - lactase
30
where are brushborder enzymes located?
embedded in walls of small intestines
31
which transporters are used to absorb glucose, galactose, and fructuse?
SGLT: glucose & galactose (exit by facillitated diffusion or GLUT2) GLUT5: fructose (exits the cell using GLUT2)
32
there is competition for absorption of the different monosaccharides. What is the order?
absorbed first → last: | galactose > glucose > fructose
33
function of pepsin
protein → peptides + AA - endopeptidase - cleaves at aromatic AA (FYW)
34
pancreas secretes ____ for protein digestion
zymogens - chymotrypsinogen - procarboxypeptidase - procolipase - prophospholipase
35
function of enterokinase
activate trypsinogen → trypsin
36
how are zymogens activated?
1. enterokinases activate trypsinogen → trypsin | 2. trypsin activates rest of zymogens
37
activated pancreatic enzymes for protein digestion
- chymotrypsin - carboxypeptidase - colipase - phospholipase
38
Pancreatitis
if trypsinogen is activated too early → digestion of the pancreas
39
how does the pancreas protect itself from being digested by protein-digesting enzymes?
1. separate trypsinogen from lysozymes in cytoplasm 2. trypsin can digest itself 3. pancreas can make trypsin inhibitor (secreted if trypsin present in pancreas)
40
___ and ___ are endopeptidases, while ___ removes AA from C-term
trypsin & chymotrypsin; | carboxypeptidase
41
brushborder enzymes for proteins
- aminopeptidase (cleave from N-term) | - dipeptidase (dipeptide → AA)
42
where are aminopeptidase & dipeptidase located?
embedded in brushborder
43
which forms of protein can be absorbed?
1. di- & tripeptides 2. AA 3. small peptides
44
absorption of di- & tripeptides
transporter: PepT1 - cotransport with H+ on both apical side - exchange with H+ on basolateral side - can be cleaved inside cell by peptidases → AA - functionally linked to NHE to keep [H] inside the cell low
45
absorption of AA
- cotransport with Na+ on apical side - exchange with Na+ on basolateral side - Na/K-ATPase used to keep concentration of Na low inside cell
46
absorption of small peptides
transcytosis
47
gastric lipase is secreted by...
chief cells
48
digestion of fat in stomach
- gastric lipase | - agitation forms smaller fat droplets
49
what is 1 instance in which gastric lipase > pancreatic lipase?
ZE syndrome: | very acidic chyme means gastric lipase is in optimal environment, but pancreatic isn't
50
why is 1 symptom of ZE syndrome malnutrition?
super acidic chyme makes all pancreatic enzymes (majority of digestion for all nutrients) less effective
51
what emulsify fats?
- bile salt (from liver) | - phospholipid lecithin (from liver)
52
purpose of emulsion?
increase SA for further digestion by pancreatic lipase
53
colipase
- pancreatic lipase can't attach on emulsified fat due to bile salts - colipase attaches bile salt on 1 end and lipase on other end → allows digestion to happen
54
micelles
- very small emulsified fat particles - hydrophilic shell - hydrophobic core (FFA, cholesterol, etc.) - small enough to be soluble
55
absorption of fat
1. FFA & monoglycerides diffuse into cell 2. go to smooth ER → re-esterify back to triglycerides 3. cholesterol enters cell via NPC1L1 (energy dependent transporter) → sER 4. everything comes together at sER → packaged at Golgi → chylomicron 5. leaves cell via exocytosis → lymphatic system → thoracic duct → subclavian vein
56
ezetimibe
drug that lowers cholesterol levels by preventing absorption | - block NPC1L1 transporter
57
function of lipoprotein lipase (LPL)
TG in chylomicrons → FFA + glycerol
58
chylomicrons is made up of...
- TG (most) - Cholesterol - PL - apoproteins
59
LPL can be found most abundantly in...
- capillaries associated with muscles - adipose tissues - capillaries associated w/ lactating boobs
60
vit B12 sources
- made by bacteria - seafood - meat - milk
61
Pernicious anemia causes
- lack of intrinsic factors being secreted by parietal cells - not enough dietary B12 - too much bac't in gut (eat up B12 before reaching ileum)
62
B12 is required for...
maturation of RBC
63
Pernicious anemia
condition where patients don't have mature RBC because Vitamin B12 is required for the maturation of RBC
64
calcium can be absorbed 2 ways...
1) paracellular | 2) hormone dependent absorption
65
hormone-dependent Ca absorption
1. Ca enters cell through Ca-channel 2. Ca bind to calbindin in cell (free Ca is very bad for cell 3. when needed, Ca is released from calbindin and exits through Ca-ATPase
66
calbindin is increased by...
vit D (calcitriol)
67
how does 1,25(OH)2 vitD3 enhance Ca absorption?
1) increase Ca channels on apical membrane | 2) increase amount of calbindin
68
iron is absorbed in which forms?
1) heme (easily absorbed) | 2) ferrous (Fe++)
69
absorption of heme iron
transporter: HCP1 (heme carrier protein) after getting into cell, dissociates → porphyrin + ferrous form
70
absorption of ferrous iron
transporter: DMT-1 (divalent metal transporter) - Fe and H cotransporter 1. ferrous form + apoferritin → ferritin 2. ferritin can be used to store lots of iron inside cell until needed
71
what happens when we want to use iron bound in ferritin?
- ferrous iron transported outside by ferroportin | - ferroportin levels regulated by hepcidin
72
ferroportin regulation
- hepcidin causes internalization of ferroportin - YES hepcidin = no ferroportin = no Fe leaving cells - NO hepcidin = yes ferroportin = yes Fe leaving cells
73
hepcidin
hormone released by liver to regulate levels of ferroportin
74
Na+ absorption
apical membrane transporters for Na+: - Na channel - Na/Cl-cotransporter - Na/H-exchanger - Na/organic solute cotransporter basolateral membrane transporters for Na+: Na/K-ATPase
75
Cl- absorption
apical membrane transporters for Cl-: - Na/Cl-cotransporter - bicarb/Cl-exchanger basolateral membrane transporter for Cl-: - Cl channel
76
how does water get absorbed?
- paracellular pathway, following solute | - active transport with SGLT transporter
77
how does K+ get absorbed?
paracellular pathway, along with water
78
SGLT is only present on __ membrane
apical
79
how is water transported with SGLT?
- Na binds, then glucose/galactose - follows glucose/galactose when it binds - about 250 molecules moved every time

PSL301 (29 decks)

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