Digestion and Absorption process of GI Flashcards
1
Q
Where does digestion start and end
A
begins in the stomach and ends in small intestine
2
Q
Where does absorption take place
A
small intestine
3
Q
2 main paths of absorption
A
cellular and paracellular
4
Q
Cellular absorption
A
lumen –> apical membrane –> intestinal epithelial cell –> basolateral membrane –> bloof
5
Q
Where are the transporters for cellular absorption
A
in membrane
6
Q
Paracellular absorption
A
intestinal epithelial cell –> lateral intercellular space –> intestinal epithelial cell
7
Q
2 types of digestive activity
A
cavital (luminal) digestion and membrane (contact) digestion
8
Q
Cavital digestion
A
digestion from action of enzymes of salivary glands, stomach and pancreas
9
Q
Membrane digestion
A
hydrolysis by enzymes of epithelial cells
10
Q
Folds of Kerckring
A
longitudinal folds of small intestine
11
Q
Function of villi and microvilli in small intestine
A
increase surface area
12
Q
Where are the villi the longest and where are they the shortest
A
longest in duodenum and shorter in terminal ileum
13
Q
Site of activity of digestive enzymes
A
microvillar surface
14
Q
Barrier that allows some passage of nutrients, water, electrolytes
A
microvillar surface
15
Q
Enterocytes
A
epithelial cells of intestine
16
Q
Function of enterocytes
A
digestion, absorption, and secretion
17
Q
Goblet cells
A
mucus-secreting cells
18
Q
Function of goblet cells
A
physical, chemical and immunological protection
19
Q
Paneth cells function
A
mucosal defense against infection and bacteria
20
Q
What controls the flux of solutes and fluid between lumen and blood
A
enterocyte membrane
21
Q
4 ways enterocytes move solutes and fluid
A
pinocytosis, passive diffusion, facilitated diffusion, and active trasport
22
Q
Where does pinocytosis occur and whats its function
A
base of microvilli and used for uptake of protein
23
Q
What movement takes place during absoprtion
A
transmural
24
Q
Monosaccharides are absorbed by
A
enterocytes
25
Three end products of carbohydrate digestion
glucose, galactose, and fructose
26
What does lactose break into
glucose and galactose
27
What does sucrose break into
glucose and fructose
28
What breaks down starch
alpha amylase
29
What can starch break into
maltose, dextrins, maltotriose
30
Transport mechanisms for absorption of carbs
co-transport and facilitated diffusion
31
GLUT 2
gets glucose, galactose and fructose from intracellular into blood
32
SGLT1
takes glucose and galactose out of the lumen into intracellular
33
GLUT5
takes fructose from lumen to intracellular
34
What kind of transport is SGLT 1
secondary active transport
35
Where is the Na/K ATPase located on the cells for carb absorption
basolateral side
36
Lactose intolerance
failure to digest carb
37
Why does lactose intolerance occur
brush-border lactase is lacking
38
Result of lactose intolerance
osmotic diarrhea-- undigested lactose remains in lumen and holds water
39
What happens to unabsorbed and undigested lactose
ferments into methane and hydrogen gas causing excess gas
40
How are proteins digested to absorbable forms
proteases in stomach and small intestine
41
Stomach protease
pepsinogen --> pepsin
42
Small intestine proteases
trypsinogen --> trypsin, chymotrypsinogen --> chymotrypsin, proelastase --> elastase, proccarboxypeptidase (A or B) --> carboxypeptidase (A or B)
43
Endopeptidases
pepsin, trypsin, chymotrypsin, elastase
44
Exopeptidases
carboxypeptidase A and B
45
What does protein breakdown into in the stomach
amino acids and oligopeptides
46
What does protein breakdown into in the small intestine
amino acids --> dipeptides and tripeptides, oligopeptides --> amino acids --> dipeptides and tripeptides
47
Function of trypsin
catalyzes hydrolysis of trypsinogen (autocatalysis)
48
Transport mechanisms for absorption of proteins
co-transport and facilitated diffusion
49
Luminal cotransporters for amino acids
Na+/amino acid cotransporter -- one for each kind of amino acid - neutral, acidic, basic, and imino
50
How do dipeptides and tripeptides cross the luminal surface
H+/ Dipeptide or Tripeptide cotransporter
51
Basolateral (Blood) side of protein absorption
facilitated diffusion- one kind for each amino acid - neutral, acidic, basic, and imino
52
Disorders of protein assimilation
occur when there is a deficiency of pancreatic enzymes or transporter problem
53
Chronic pancreatitis and cystic fibrosis
deficiency of pancreatic enzymes
54
Congenital trypsin absence
absence of trypsin makes it seem like all pancreatic enzymes are gone
55
Cystinuria
genetic disorder where amino acids are secreted in the feces
56
Process of cystinuria
defect in or absence of Na+/amino acid co-transporter
57
Hartnup disease
can't absorb neutral amino acids (tryptophan)
58
Genetics of Hartnup disease
recessive genetic disorder
59
Symptoms of Hartnup disease
diarrhea, red scaly skin, photosensitivity, short stature
60
Urine samples of Hartnup disease
abnormally high excretion of neutral amino acids (trypotophan) and their by products (serotonin)
61
Cystic fibrosis transmembrane conductance regulator (CTFR)
chloride ion channel
62
Mutation in CTFR
associated with deficiency of pancreatic enzymes
63
What organ is the first to fail in cystic fibrosis
pancreas
64
How are lipids digested to absorbable forms
lipases in stomach and small intestine
65
Triglyceride breakdown into
via lingual, gastric, and pancreatic lipases into monoglyceride and 2 fatty acids
66
Cholesterol ester breakdown into
via cholesterol ester hydrolase into cholesterol and fatty acid
67
Phospholipid breakdown into
via phospholipase A2 into lysolechitin and fatty acid
68
Why lipid breakdown is complicated
lipids need to be solubilized in micelle and transported to apical membrane for absorption
69
Lingual and gastric lipases...
initiate lipid digestion in stomach
70
Where are lipid droplets emulsified
in stomach by dietary proteins -- with NO bile acids
71
What enzyme in the stomach helps lipid digestion and how
CCK because it slows gastric emptying allowing more time for breakdown
72
Where does most lipid digestion occur
small intestine
73
Function of bile salts
emulsify fat
74
Pancreatic enzyme and lipid digestion
enzymes secreted into small intestine to complete digesiton
75
Pancreatic lipase
inactivated by bile salts
76
Colipase
secreted an inactive for and activated by trypsin and binds to pancreatic lipase to displace the bile salt
77
Cholesterol ester hydrolase
catalyze cholesterol production and hydrolyze triglycerides into glycerol
78
Phospholipase A2
proenzyme is activated by trypsin
79
Optimal pH for pancreatic lipase
6
80
Products of lipid digestion
micelles
81
Micelle structure (5)
bile salt, hydrophilic side, hydrophilic side, nonpolar lipid and phospholipid
82
5 steps of processing a lipid
1. solubilization by micelles, 2.diffusion of micellar content across apical membrane, 3.reesterification, 4.chylomicron formation, 5.exocytosis of chylomicron
* *includes Apo B ** on chylomicron
83
No ApoB on chylomicron can lead to
abetalippoproteinemia and you can't absorb dietary lipids
84
Abnormality of lipid assimilation
steatorrhea
85
Pancreatic insufficiency
failure to secrete adequate pancreatic enzymes
86
Function of pancreatic enzymes
regulate acidity of duodenum
87
Zollinger-Ellison syndrom
gastric secreting tumor causing H+ increase and overload of acid in duodenum
88
Pancreatitis
impaired HCO3 secretion and impaired enzyme secretion
89
Deficiency of bile salt
interferes with formation of micelles
90
Causes of bile salt deficiency
ileal resection and small intestinal bacterial overgrowth (SIBO)
91
Ileal resection and bile salt deficiency
interrupts enterohepatic circulation of bile salts and bile salt pool is reduced
92
Small intestinal bacterial overgrowth (SIBO)
bacteria deconjugate bile salts causing failure of micelle formation and fat malabsorption
93
Two main causes of small intestinal bacterial overgrowth
decrease in gastric acid secretion and small intestin dysmotility
94
Clinical presentation of SIBO
chronic diarrhea, weight loss, and malabsorption
95
Tropical sprue
reduction in number of intestinal epithelial cells which reduces microvillar surface area
96
Why is lipid absorption impaired in tropical sprue
because surface area for absorption is decreased
97
S/S of tropical sprue
steatorrhea, deficient in folate and B12, diarrhea
98
Treatment for tropical spure
tetracycline and folate
99
Non-tropical sprue (celiac sprue)
autoimmune disorder where antibodies develop against gluten
100
S/S of non-tropical sprue
malabsorption and deficiency in vitamin B12, folate, iron, calcium, vitamin D, and vitamin A
101
Prevalence of Non-tropical sprue
caucasian and european ancestry and woman
102
GI symptoms of celiac spure
abdominal pain, constipation, diarrhea, steatorrhea
103
Non Gi symptoms of celiac sprue (due to nutrient deficiency)
tingling in hands, itchy skin, easy bruising
104
Fat soluble vitamins
A, D, E, K
105
Mechanism of fat soluble absorption
same as lipids
106
Water soluble vitamins
B1,2,3,12, C, biotin, folic acid, nicotinic acid, and pantothenic acid
107
How are water soluble vitamins absorbed
Na+ dependent cotransport in small intestine
108
Vitamin B12 importance
complexes with other proteins-- R protins, intrinsic factor, and transcoalbumin II
109
2 disruptions in absorption of vitamin B12
gastrectomy and gastric bypass
110
Gastrectomy
loss of parietal cells and intrinsic factor source
111
Gastric bypass
exclusion of stomach, duodenum, and proximal jejunum alters absorption of vitamin B12
112
Pernicious anemia
stomach doesn't produce enough intrinsic factor and decrease in B12
113
Common causes of pernicious anemia
atrophic gastritis and autoimmune condition
114
Atrophic gastritis
chronic inflammation of stomach mucosa causing loss of parietal cells
115
Abnormalities of absorption of vitamin D
Rickets, osteomalacia due to inadequate Ca2+ absorption b/c deficient vitamin D
116
2 sources of D3 in vitamin D formation
Sunlight and Diet
117
Vitamin D effects of body (3)
increase in gut Ca2+ absorption, increase bone calcification and increase bone resorption
118
Enzyme that makes vitamin D usable to body
1 alpha hydroxylase
119
Usable form of vitamin D
1,25 Dihydroxy D3
