Chapter 11- Imi Biochem Flashcards
(129 cards)
1
Q
what is digestion
A
hydrolysis of complex food substances into simple units such as monosaccharides, amino acids, fatty acids, and glycerol
2
Q
what is absorption
A
transport of the products of digestion and of vitamins, minerals, and water across the intestinal epithelium to the lymphatic or blood circulatory systems
3
Q
what is digestion and absorption
A
GI tract, secretions from salivary glands, liver and gall bladder, and pancreas that are interrelated
4
Q
Secretory and absorptive activities are regulated by
A
hormones
5
Q
intestinal surface area enhanced by
A
finger-like villi
6
Q
GI Tract Is controlled by
A
Central Nervous System and the Enteric Nervous System
7
Q
2 plexus of GI system
A
submucosal and myenteric nerve plexus
8
Q
function of mouth
A
mixed with saliva, chewed to break up large particles, propelled into esophagus
9
Q
saliva secretes, tonicity of solution, pH, principle ions, modulation
A
1-2L secreted daily, hypotonic solution (pH 7.0), principle ions (Na+, K+, Cl-, HCO3-), aldosterone modulate Na+ & K+ levels
10
Q
mucin function, composition
A
responsible for lubricating action, mixture of glycoproteins containing 60-85% oligosaccharides by weight
11
Q
Amylase function
A
catalyze the hydrolysis of α(1-4) glycosidic linkages of starch and glycogen
12
Q
other enzymes secreted from the mouth
A
Carbonic anhydrase, lipase, phosphatase, protease
13
Q
esophagus
A
a muscular tube, has no digestive function but secrete mucus to protect the esophageal mucosa from excoriation
14
Q
stomach
A
Store food temporarily, retards its entry into SI
15
Q
pepsin
A
secreted by stomach, substantial chemical and enzymatic digestion is initiated, particularly of proteins
16
Q
formation of pepsin
A
[H+] activate pepsinogen to form pepsin, aid in maintaining the sterility of upper GI tract
17
Q
stomach also secretes
A
intrinsic factor, lipase, gelatinase, chymosin (rennin), mucus, HCl, Gastrin
18
Q
pH of stomach prevents
A
pH is so low prevents bacterial survival except H. pylori (survives at pylorus)
19
Q
intrinsic factor required to absorb what, where
A
vitamin B12 in the ileum
20
Q
Most digestion and absorption of food constituents occurs in the
A
Small intestine
21
Q
small intestine major site for
A
absorption of water & electrolytes
22
Q
parts of small intestine
A
duodenum, jejunum, ileum,
23
Q
Wall of small intestine consists of
A
4 layers: mucosa, submucosa, muscularis externa, serosa
24
Q
villi, enterocyte, microvilli allow for what and appearance
A
large surface area, increase the absorptive surface, a brush like appearance
25
digestion in small intestine require
biliary & pancreatic secretions that are emptied into the duodenum
26
Bile is formed and secreted continuously by
polygonally shaped liver parenchymal cells called hepatocytes
27
bile is concentrated, stored, emptied into the duodenum by
gallbladder
28
composition of bile
Contains bile acids, bile pigments, cholesterol (gallstones), phosphatidylcholine, & electrolytes
29
contraction of gallbladder mediated by
cholecystokinin
30
mechanism of bile synthesis
senescent red cell broken down -> bilirubin -> added to albumin ->forming free bilirubin in hepatocyte -> addition of glucuronic acid -> conjugated bilirubin -> bile formation
31
Endocrine function of pancreas
secrete insulin, glucagon, somatostatin for regulation of metabolism of CHOs and other substances
32
Exocrine function fo pancreas
synthesis & secretion of digestive enzymes and bicarbonate-rich fluids
33
digestive enzymes and bicarbonate rich fluids from pancreas released into lumen upon
stimulation by the vagus nerve or by cholecystokinin
34
pH of pancreatic juice
Alkaline b/c high content of HCO3-
35
pancreatic juice are alkaline to
neutralize acidic chyme from the stomach aided by the bile & SI juices
36
pancreatic juice contain
proenzymes trypsynogen, chymotrypsinogen, procarboxypeptidases, & proelastase
37
proenzymes trypsynogen, chymotrypsinogen, procarboxypeptidases, & proelastase activated by
activated by trypsin in the intestinal lumen
38
trypsin activated by
trypsinogen converted to trypsin by enteropeptidase located in the brush border of the jejunal mucosa
39
pancreatic juice contains trypsin inhibitor to
protect against indiscriminate autodigestion from intraductal activation of trypsinogen
40
Other enzymes of pancreatic juice are
prophospholipase, cholesteryl ester hydrolase, lipase and procolipase, amylase, ribonuclease, deoxyribonuclease
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major function of large intestine
absorption of water, Na+, & other electrolytes
42
large intestine harbors large numbers of anaerobic bacteria to
metabolize CHOs to lactate, short-chain fatty acids (acetate, propionate, butyrate), & gases (CO2, CH4, & H2)
43
gastrointestinal hormones are
Chemical messengers that regulate intestinal functions (e.g., motility and secretion- autonomic nervous system also regulates)
44
Endocrine cells of the GI tract are interspersed with
mucosal cells
45
GI tract is described as the
largest endocrine organ in the body
46
Major GI hormone
gastrin ghrelin, cholecystokinin, glucose dependent insulinotropic polypeptide (GIP), secretin, polypeptide YY, somatostatin
47
gastrin source and function
Source: G-cells of gastric antrum and duodenum Function: stimulates acid (HCl) secretion from parietal cells and histamine from enterochromaffin-like cells; promotes proliferation of gastric mucosa
48
ghrelin source and function
Source: A-cells of gastric fundus; other segments of GI tract; hypothalamus Function: promote food intake, gastric motility; stimulates growth hormone secretion
49
cholecystokinin source and function
Source: I-cells of duodenum and jejunum; central nervous system Function: stimulates gall bladder and pancreatic enzyme secretions; decreases appetite
50
glucose dependent insulinotropic polypeptide (aka Gastric inhibitory peptide-GIP) source and function
Source: K-cells of the duodenum and jejunum Function: promote insulin secretion from beta-cells of pancreas (incretin effect); FA synthesis in adipose tissue
51
secretin source and function
Source: S-cells of the duodenum and jejunum also present in brain Function: stimulates the secretion of bicarbonate-rich fluids from the duct cells and biliary tract; augments the action of CCK and decreases gastric acid secretion
52
polypeptide YY source and function
Source: L-cells of distal small and large intestine Function: inhibits food intake
53
somatostatin source and function
Source: D-cells of the GI tract and pancreas; hypothalamus Function: inhibits secretion of GI tract hormones, growth hormone, and thyrotropin
54
GI hormones obtained from proglucagon cleavage by cell-specific pro hormone convertases
glucagon-like peptide 1 (GLP-1), glucagon-like peptide 2 (GLP-2), Oxyntomodulin
55
glucagon-like peptide 1 (GLP-1) source and function
Source: L-cells of distal small and large intestine Function: promotes insulin secretion from beta cells of pancreas (incretin effect) and promotes beta-cell growth; suppresses pancreatic glucagon secretion by alpha-cells; delays gastric emptying
56
glucagon-like peptide 2 (GLP-2) source and function
Source: L-cells of distal small and large intestine Function: promotes intestinal mucosal growth and repair; inhibits gastric secretion
57
Oxyntomodulin source and function
Source: L-cells of distal small and large intestine Function:inhibits food intake; inhibits gastric motility and acid production
58
precursor to glucagon
proglucagon
59
proglucagon goes to
pancreatic alpha-cells, brain, L-intestinal cells
60
gastrin secreted from and function
Secreted from the stomach and plays an important role in control of gastric acid secretion
61
gastrin released in response to
chemical, mechanical, or neural stimuli on the G cell Hypoglycemia, increased calcium ions
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main physiological actions of gastrin
Stimulation of acid secretion by parietal cells, Secretion of pepsin by chief cells, Increase in gastric mucosal blood flow, Stimulation of gastric motility, Promotion of the growth of oxyntic mucosa and exocrine pancreatic tissue
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gastrin is suppressed by
acidification of the antral mucosa & by all members of the secretin family
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when H+ not secreted owing to destruction or absence of functioning parietal cells leads to
increased plasma gastrin levels
65
increased plasma gastrin levels causes
pernicious anemia, atrophic gastritis, Zollinger-Ellison syndrome
66
hyper secretion of acid, peptic ulcer disease, and hyperplasia of gastric mucosa are attributed to
Zollinger-Ellison syndrome
67
If Intracellular pH 7, luminal pH 1 parietal cells secrete
H+ at a concentration a million-fold higher than that inside the cell, contain the largest number of mitochondria
68
HCl is secreted into the gastric lumen by
H+, K+-ATPase, HCO3- is secreted into blood
69
what stimulates acid secretion from parietal cell
Acetylcholine, gastrin, histamine (H2 receptor), & bombesin
70
Secretion of gastric acid is suppressed by
anticholinergic agents (atropine), H2 receptor antagonists (cimetidine, ranitidine), prostaglandin E derivatives, substituted benzimidazoles (omeprazole, pantoprazole)
71
second messengers in acid secretion from parietal cells
cAMP (H2 receptor coupled to Adenyl Cyclase) & Ca2+ (cholinergic receptor coupled)
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parietal cells secrete
H+ and Cl-
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peptic ulcer disease caused by
an imbalance of acid secretion by the parietal cells and lack of mucosal protective barriers due to drug (NSAIDs) or bacterial infection (Helicobacter pylori)
74
NSAIDs inhibit
COX1 and COX2
75
celecoxib, cytoprotective effects by misoprostol
COX 2 inhibitors
76
H. pylori treated with
antibiotics, anti-secretory agents (H2-Receptor antagonists or proton pump inhibitors), & bismuth salts
77
H. pylori produces bacterial urease that does what
urea converted to ammonia and CO2 causing increased pH which increase levels of gastrin and increases acid production
78
H. pyroli also produce vacuolating cytotoxin and CagA that causes
ulcerogenesis, gastritis and a risk factor for adenocarcinoma of the antrum and the body of the stomach & non-Hodgkin's lymphoma of the stomach
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H. pylori detected by
serological markers and breath test
80
cholecystokinin secreted as a result of
stimuli caused by products of digestion of proteins and lipids
81
cholecystokinin secretion terminated when
digestion products are absorbed or migrate into the lower portions of the GI tract
82
principal physiological actions of cholecystokinin
stimulate gallbladder contraction, to relax the sphincter of Oddi, and to stimulate secretion of pancreatic juice rich in digestive enzymes
83
other functions of cholecystokinin
stimulate bicarbonate-rich fluid secretion, insulin secretion, and intestinal motility
84
stimulates release of secretin
Chyme in the duodenum
85
A.a. sequence of secretin is similar to
glucagon, vasoactive inhibitory peptide (VIP), and gastric inhibitory peptide (GIP)
86
Secretin hormone action
mediated by membrane-bound adenylate cyclase and increased intracellular cAMP
87
Gastric inhibitory peptide stimulated by
glucose and lipids in the duodenum
88
main functions of gastric inhibitory peptide
stimulate insulin secretion that prepares the appropriate tissues for the transport and metabolism of nutrients obtained from the GI tract, and inhibit gastric secretion and motility
89
incretin promote
insulin secretion
90
incretins are
glucagon-like peptide 1 and gastric inhibitory peptide
91
Predominant digestible CHOs are
starches (amylose & amylopectin), glycogen, disaccharides (sucrose & lactose)
92
Intraluminal hydrolysis of starch and glycogen by
α-amylase to oligosaccharides of variable length and structure
93
oligosaccharidases
Brush-border surface hydrolysis of oligosaccharides and disaccharides (e.g., sucrose, lactose, & trehalose) to their monomers
94
Intolerance of other carbohydrates
sucrose and α-limit dextrin
95
Transport of monosaccharides (e.g., glucose, galactose, & fructose) into enterocytes
Na+, K+-ATPase
96
alpha amylase cleaves
alpha (1-4) linkage
97
stomach secretes
pepsinogen
98
pancreas secretes
trypsin, chymotrypsin, carboxypeptidase, elastase
99
Brush-border secretes
aminopeptidase, dipeptidase, tripeptidase
100
endogenous proteins promote
Enzymes, glycoproteins, and mucins secreted from the salivary glands, stomach, intestine, biliary tract, and pancreas (20-30g/day) Rapid turnover of the GI epithelium (30g/day) Plasma proteins that normally diffuse into the intestinal tract at a rate of 1-2g/day
101
free a.a. transported into enterocytes by what four active, carrier-mediated, Na+-dependent transport systems
Neutral a.a.; basic a.a. (Lys, Arg, His) & cystine; Asp & Glu; Gly & Imino acids
102
a few days after birth neonates have ability to absorb
intact proteins
103
by absorbing intact proteins neonates can acquire
passive immunity by absorbing Igs in colostral milk
104
defects in neutral amino acid transport
hartnup's disease
105
defect in basic a.a. and cysteine transport
cystinuria
106
defect in asp and glutamate (carboy group) transport
dicarboxylic aminoaciduria
107
cyanogenbromide cleaves
methionine at c-terminus
108
defect in transport of glycine
aminoglycinuria
109
trypsin cleaves
arginine and lysine at c-terminus
110
chymotrypsin cleaves
tryptophan, tyrosine, and phenylalanine
111
to determine pancreatic problem admin N-benzoyl-L-tyrosyl-p-aminobenzoic acid
check urine for PABA, if no PABA chymotrypsin not working
112
Hydrolysis of triglyceride into monoglyceride and free fatty acids is accomplished predominantly by
pancreatic lipase
113
steatorrhea
more than 90% of ingested lipid not absorbed
114
Gluten-sensitive enteropathy or celiac disease
gliadins leads to production of Ab to endomysium of smooth muscle
115
Cyctic fibrosis (CF)
a disease of multiple exocrinopathy and generalized malabsorption due to lack of delivery of pancreatic digestive enzymes to the small intestine
116
chronic alcoholism
generalized malabsorption of major foods and vitamins b/c of liver and pancreatic involvement and mucosal dysfunction
117
cholera secretes ZOT toxin which effects
tight junctions, zonula occludens toxin
118
diarrhea
water excreted in feces greater than 500mL
119
treatment for diarrhea
oral glucose and NaCl
120
Na+ absorption regulated by
aldosterone
121
K+ absorbed by
passive diffusion
122
If the intestinal contents become hyperosmolar then
water enters the lumen to produce iso-osmolarity and fluid and electrolyte loss occur
123
Bile salts in colon inhibit absorption of
water and Na+ and cause diarrhea
124
ADP-ribosylation of Gsα
cholera toxin
125
cholera toxin mechanism
ADP-ribosylation of Gsalpha -> activates adenyl cyclase -> increases cAMP -> continuous stimulation of CFTR Cl- channel -> increased osmolarity in intestinal lumen -> passive water excretion -> diarrhea
126
ADP-ribosylation of Giα
pertussis toxin
127
E. Coli
non-bloody diarrhea, hemorrhagic colitis, hemolytic uremic syndrome, death
128
diphtheria toxin
ADP-ribosylation, inhibit (elongation factor) eukaryotic protein synthesis
129
pancreatic islet-cell tumor causes
severe watery diarrhea
