CNS Primer Flashcards
1
Q
Structures of the alimentary tract
A
mouth, tongue, teeth, and throat
2
Q
the chief cells of the stomach secrete
A
lipase & pepsinogen
3
Q
lipase breaks
down dietary triglycerides into
A
into free fatty acids and diglycerides
(diacylglycerols),
4
Q
pepsinogen is the precursor of,
A
pepsin
5
Q
pepsin initiates the hydrolysis of
A
proteins
6
Q
parietal cells of the stomach secrete
A
Intrinsic factor (IF) & HCl
7
Q
Intrinsic factor is a protein required for absorption of
A
vitamin B12,
8
Q
Mucous cells of the stomach secrete mucus
containing
A
glycoproteins and bicarbonate
9
Q
Gastric acid performs a number of preliminary digestive roles that require an
acidic environment, including
A
- destruction of microorganisms,
- activation of pepsinogen to
pepsin, - activation of intrinsic factor,
- denaturation (loss of three-dimensional conformation) of
macromolecules, - facilitation of the breakdown of protein and polypeptides by pepsin.
10
Q
The presence of food protein in the stomach triggers gastric endocrine cells to secrete
A
gastrin
11
Q
Gastrin acts on gastric parietal and chief cells to stimulate intragastric secretion of
A
HCL & pepsinogen
12
Q
gastrin secretion is inhibited by increased/decreased intragastric acidity.
A
Increased
13
Q
Peristaltic contractions of the distal stomach propel digesta toward the __________.
Simultaneously, the _______________ contracts in opposition to gastric peristalsis, but does
not close.
A
gastric pylorus
14
Q
common name for the luminal surface of the small intestine
A
brush border
15
Q
brush border is composed of
A
microvilli
16
Q
microvilli increase/decrease the absorptive surface area of the small intestine
A
increase
17
Q
Absorptive _______ originate from stem cells in the intervillar crypts. Following their migration to the luminal surface of the mucosa, __________ fully differentiate, survive about 72 hours, undergo apoptosis (preprogrammed cell death) and lose their attachment to the mucosal basement
membrane (“desquamation”).
A
enterocytes
18
Q
most proximal upper section of the small intestine where chemical
degradation of partially digested food into individual nutrients begins.
A
short duodenum,
19
Q
second section of
the small intestine,
A
second section of
the small intestine,
20
Q
distal small intestine,
A
ileum,
21
Q
Acidic chyme entering the proximal duodenum stimulates the enteric secretion of
A
secretin
22
Q
Secretin stimulates pancreatic secretion of ________ into
the ductal system that terminates in the common bile duct.
A
bicarbonate
23
Q
fat or protein
entering the proximal duodenum stimulate duodenal secretion of
A
cholecystokinin
24
Q
Cholecystokinin stimulates pancreatic secretion of ________ into the ductal systemand stimulates gall bladder
contraction, propelling bile into the common bile duct.
A
zymogens
25
(inactive digestive enzyme precursors)
zymogens
26
Increasing duodenal distension triggers secretion of
gastric inhibitory
peptide
27
This peptide inhibits gastric motility and slows the rate of further gastric emptying when increasing duodenal distension
gastric inhibitory
peptide
28
Pancreatic zymogens that play major roles in food digestion include
- trypsinogen
- proelastase
- chymotrypsinogen
- procolipase
- procarboxypeptidase A
- procarboxypeptidase B.
29
When pancreatic zymogens reach the small intestine,
duodenal enterocytes secrete ______, which converts trypsinogen to trypsin.
enterokinase
29
enterokinase enzyme is required for activation of
trypsin
30
trypsin zymogens to
- elastase
- chymotrypsin
- colipase
- carboxypeptidase A
- carboxypeptidase B
31
Trypsin,
chymotrypsin and elastase are ______ proteases and ____peptidases (hydrolyze peptide bonds within polypeptides).
serine proteases
endopeptidases
32
the proteases require a serine is at the enzymes’ active sites
serine proteases
33
This type of enzyme hydrolyzes peptide bonds within polypeptides
endopeptidases
34
Carboxypeptidases are _____-requiring metalloenzyme exopeptidases that cleave single carboxyterminal amino acids from polypeptides.
zinc
35
Secreted by the pancreas, ________ performs initial digestion of starches to produce glucosyl oligosaccharides and
disaccharides
amylase
36
Secreted by the pancreas, ______ hydrolyzes dietary fats that have been emulsified by bile salts into fatty acids and glycerol
lipase
37
Secreted by the pancreas, ____________ cleaves cholesteryl esters;
ribonuclease and deoxyribonuclease.
cholesteryl esterase
38
The brush
border enzymes that complete the final steps in the hydrolysis of amylase-digested carbohydrates to
monosaccharides and of protease-digested proteins to absorbable free amino acids, dipeptides
and tripeptides.
Ectozymes
39
The categories of ectozymes produced by enterocytes and attached to microvillar surfaces of the small intestine
- oligosaccharidases
- disaccharidases
- pepidases
40
Pancreatic bicarbonate buffers ____ into a weaker acid
gastric HCl
41
The efficiency of digestive
enzymes is affected primarily by ____ pH.
local
42
The pH optimum for salivary amylase is a pH
6.75-7.00
43
The pH optimum for gastric pepsin and lipase is a pH
1.5-3.5
44
Enzymes that are deactivated by the presence
of free protons include
gastric lipase, salivary amylase and lingual lipase.
45
gastric lipase, salivary amylase and lingual lipase function most efficiently at _____ or higher _____ pH.
neutral, alkaline
46
primary role of
the liver in food digestion and nutrient absorption.
bile excretion
47
Bile contains
- cholic acid
- chenodeoxycholic acid
- taurine
- glycine
- cholesterol
- electrolytes
- water
48
pancreatic lipase and colipase hydrolyze triglycerides and
diglycerides to release
monoglycerides (monoacylglycerols) and free fatty acids.
49
The absorption of monoglycerides, free fatty acids, cholesterol, phospholipid digestion products, and fat-soluble foods depends on their ability to aggregate with bile salts and incorperate with ____.
micelles
50
the spherical structure representing the collection of lipid soluble dietary
subcomponents surrounded by a layer of water soluble bile salts.
micelles
51
Within the endoplasmic reticulum of enterocytes, lipids and lipid soluble compounds are
repackaged into large protein-coated (and therefore water soluble) ________
chylomicrons
52
chylomicrons are
secreted into the lacteals, flow through the lymphatic system and enter the circulation via the _______ duct.
thoracic
53
Diffusion utilizing the potential energy created by a difference in
nutrient concentration across a membrane to move nutrients from an area of higher concentration
to an area of lower concentration.
Passive diffusion (or simple diffusion)
54
Lipid soluble compounds enter intestinal cells by ____________ from the brush border into the cell cytosol.
passive diffusion
55
Diffusion moving down in concentration gradient and nutrient is attached to a lipid soluble membrane carrier protein that easily passes through membranes even with the attached nutrient.
Facilitated diffusion (carrier-mediated transport)
56
Most carbohydrates are transported across
biological membranes via _______
facilitated diffusion.
57
The process where a nutrient moves through mucosal cell
membranes against a concentration gradient. This process requires the participation of a
membrane carrier protein (receptor) and consumes biochemical energy provided by ATP.
active transport (solute pumping),
58
Most amino acids and ions are absorbed via
active transport (solute pumping),
59
Factors that preserve intestinal barrier function
include
antibacterial and antiviral secretions of nonpathologic microflora
- endogenous mucous secretions,
- intercellular “tight junctions,”
- intestinal epithelial secretion of lectins and anti-
adhesion glycoproteins,
- peristaltic movement of digesta
- enterocytic filtration
60
(ysosomal hydrolysis of pathogens and toxins within enterocytes
enterocytic filtration
61
Antimicrobial defenses within the
intestinal tract rely heavily on the secretion of secretory Ig?
IgA (sIgA)
62
sIgA is secreted by
by gut-associated lymphoid
tissue (GALT).
63
GALT
gut-associated lymphoid
tissue
64
GALT (gut-associated lymphoid tissue) contains about 50-60% of the total number of immune cells in
the body, and as the “first line of defense” against
environmental assault, GALT provides both _______ immunity and ________ immunity
via secretory IgA.
cell-mediated; humoral
65
“Autoimmune-like diseases” may occur when food components or bacterial antigens share a
common __________ with both a virus or other pathogenic micro-organism to which the host has been exposed previously and a host cell membrane component. Antibodies
to the pathogen, triggered by the exogenous antigen, may cross react with the host cell component, generating an autoreactive immune response that mimics an autoimmune disease.
antigenic determinant (epitope)
66
Small molecules (such as monosaccharides) are absorbed by enterocytes via
direct transcellular uptake.
67
large molecules do not undergo transcellular uptake and normally are prevented from passing between enterocytes (paracellular uptake) by intercellular ________
tight junctions
68
Measuring the rate of urinary excretion of a test dose of a nonmetabolizable and normally nonabsorbable large molecule, such as _____ provides information on the integrity of the intercellular mucosal barrier.
lactulose (galactose + fructose),
69
In a urinary excretion test...
A) mannitol (WNL/H) + lactulose (H) indicates...
B) mannitol (L) + lactulose (L) indicates...
C) mannitol (L) + lactulose (H) indicates...
A) increased small intestinal permeability
B) small intestinal malabsorption
C) increased small intestinal permeability and small intestinal malabsorption
*use of lactulose to detect increased intestinal permeabilitymay be
associated with a high incidence of false positive results.
70
Intestinal impermeability may be restored by
- reduce the amount of
proteinaceous residue reaching the ileum,
- increase epithelial integrity
- support the GALT.
71
the major intestinal extracellular antioxidant with the highest tissue content in human gastric and duodenal epithelia.
Glutathione (GSH)
72
The amino acid that is the required primary fuel source for enterocytes. This AA
provides substrates for the enteric tricarboxylic acid cycle and production of polyamines and DNA. It is the rate-limiting
precursor for glutathione synthesis within enterocytes.
Glutamine
73
During illness, trauma and
stress, this amino acid is diverted to the immune system, depleting enterocytes of glutamine and glutathione.
Glutamine
74
Inadequacy of this AA produces thinning of villi with decreased digestive function, decreased absorptive function, loss of intestinal barrier integrity,
and increased translocation of antigens and pathogens from the intestinal lumen into the extracellular fluid and blood.
Glutamine
75
Structures of the large intestine
ascending colon, transverse colon, descending colon, and
sigmoid colon.
76
major functions of the large intestine are to
- reabsorb water from the digesta,
- absorb vitamins produced by intestinal bacteria,
- provide an environment conducive to the
fermentation of dietary fiber by resident microbes,
- eliminate dried residues (undigested and
unabsorbed material) as feces.
77
products of _____ fermentation that avoid microbial ingestion are
primary energy sources for colonocytes, support colonocyte metabolism and maintain colonocyte
apoptotic synchrony.
dietary fiber
78
Unfermented fractions of ingested dietary fiber exhibit the “classical”
functions of stool softening and binding for fecal excretion of
- bile salts,
- cholesterol,
- steroid hormones and their metabolic derivatives.
79
Examples of _____ dietary fiber include the beta- glucans (including
arabinogalactans and lactoferrin), gums, mucilages, and pectins. This dietary fiber comprises
10-20% of the total dietary fiber content of fruit, okra, beans, turnips, oats, parsnips, sea
weeds, and prunes.
soluble
80
Examples of ________ dietary fiber include the celluloses and lignins.
insoluble
81
Hemicellulose is classified as a ______ dietary fiber
soluble + insoluble
82
Most adults with healthy colons should ingest ____ g of soluble fiber daily.
25-35
83
Foods rich in ____ dietary fiber often contain lipase inhibitors that prevent the digestion of dietary fat and may induce deficiencies
in essential fatty acids and fat-soluble vitamins.
soluble
84
_____ fiber intakes >50 g/day may inhibit the digestion of non-fiber carbohydrate, increasing the amount of sugar and starch reaching the colon.
Soluble
85
Examples of _________ dietary fiber include oat hulls, methylcellulose and wood pulp cellulose.
nonfermentable
86
Non fermentable dietary fiber components function in the human colon to
increase the bacterial mass of the stool
- decrease the absorption of glucose and increase the glucose content of
stool
- dilute pathogens and
toxins in digesta and stool
- increase rate of passage
- inhibit the inflammatory responses to bacterial infections
- inhibit phagocytotic capacity of intestinal macrophages
87
The most common microorganisms
in the human stomach and, because it is the next residence available to organisms moving with
ingesta, the duodenum, are
- Lactobacilli,
- Streptococci
- yeasts
88
Small pH differences along the small intestine favor the following micro-organisms
- Lactobacilli,
- Enterobacteriaceae,
- Streptococci,
- Bacteroides,
- Bifidobacteria
- Fusobacteria
89
The most common microorganisms in the human colon are
- Bifidobacteria,
- Lactobacilli,
- Streptococci,
- Bacteroides,
- Fusobacteria,
- Enterobacteriaceae,
- Pseudomonas,
- Clostridia,
- Proteus species,
- yeasts and protozoa.
90
The most beneficial individual species of micro-organisms for the human GI tract are
- Bifidobacterium
bifidus (bifidum),
- Bifidobacterium infantis,
- Lactobacillus acidophilus,
- Lactobacillus
bulgaricus,
- Lactobacillus brevis,
- Lactobacillus casei,
- Lactobacillus cellobiosus,
- Lactobacillus fermenti,
- Lactobacillus leichmannii,
- Lactobacillus plantarum,
- Lactobacillus
rhamnosus,
- Lactobacillus salivarius,
- Lactobacillus sporogenes,
- Saccharomyces boulardii,
- Enterococcus faecium,
- Streptococcus thermophilus.
91
the most common microorganisms in the healthy human digestive tract and are the predominant microbes in human breast milk
Bifidobacteria
92
Bifidobacteria enhance epithelial barrier function by
- reducing pathogenic load
- reduce risk for developing colon cancer bymetabolizing
carcinogens and procarcinogens.
- suppress growth of pathogenic species by
maintaining a slightly acidic colonic pH,
- binding to adhesion proteins on pathogens
- secretion of adhesion-inhibiting proteins,
- secretion of broad-
spectrumantibiotics
- secretion of antiviral L-bifidus factor
- stimulation of GALT phagocytosis of pathogens.
93
This micro-organism ferments dietary fiber carbohydrates to lactic acid and short chain fatty acids, contributing to the slightly acidic colonic
pH.
Lactobacilli
94
Lactobacolli enhance epithelial barrier integrity by
- reducing pathogenic load
- reduce risk for developing colon cancer by binding heterocyclic mutagens,
- deconjugating bile
acids
-binding and metabolizing cholesterol.
95
Lactobacilli also ameliorate symptoms of lactose intolerance in individuals with inadequate lactase production by secretion of
beta-galactosidase (lactose →glucose + galactose).
96
Lactobacilli suppress growth of pathogenic species by a variety of mechanisms, including
- maintaining a slightly acidic colonic pH,
- binding to adhesion proteins on pathogens
- secretion of adhesion-inhibiting proteins,
- competing for adhesion sites on enterocytes,
-secretion of species-specific antibiotics
- secretion of hydrogen peroxide,
-stimulation of GALT production and secretion of secretory IgA (sIgA),
- inhibition of bacterial
enzymes
- stimulation of
colonic peristalsis
97
Saccharomyces boulardii (yeast) found in both the small and large intestine function to
- antagonistic to Candida albicans,
- inhibit the effects of cholera toxin,
- inhibit the adhesion of amoeba to the intestinal brush border,
- stimulate enterocyte secretion of brush border enzymes
- stimulate GALT production and secretion of sIgA.
98
Microbial fermentation
of fermentable dietary fibers results in the production of short chain fatty acids (SCFAs), individually called
acetate, propionate, butyrate
99
Butyrate is metabolized to
_____ within colonocytes.
acetyl CoA
100
butyrate key functions include...
- stimulates secretion of enteroglucagon,
- stimulates T-lymphocyte proliferation in GALT,
- attenuates B- lymphocyte reactivity in GALT,
- inhibits TNF-α - induced activation of the nuclear transcription factor procarcinogenic NF-κB
in colonocytes,
- inhibits TNF-α - induced secretion of pro-inflammatoryIL-8 by colonocytes,
- inhibits growth of pro-inflammatory Clostridium species,
-required for the maintenance of colonocyte apoptotic destiny.
101
Butyrate insufficiency within the colon results in
- depletion of intracolonocyte acetyl CoA,
- increased intracolonocyte cyclic AMP concentration,
- inhibition of apoptosis, failure of intercellular “tight junctions,”
- impairment of epithelial barrier integrity in the colon
- increased large intestinal epithelial permeability.
*if secondary to inadequate fermentation of butyrate precursor... intraepithelial inflammation, systemic illness and inflammatory syndromes that mimic
autoimmune disease.
102
The intestinal tracts of
nonbreastfed infants are characterized by [H/L] numbers of Bifidobacteria and Lactobacilli and
high numbers of Enterococci, Coliforms and Clostridia.
LOW
103
Lack of sufficient amounts of _______ in the colon decreases the rate of passage, increasing the time
available for absorption of water by colonocytes and providing increased exposure of
colonocytes to toxins, mutagens and carcinogens.
dietary fiber
104
Intracolonocyte ______ deficiency produces “leaky tight junctions” with an
increase in intestinal permeability, as well as increased risk for energy deficit in colonocytes.
acetyl CoA
105
Decreased colonocyte oxidation of butyrate produces delayed colonocyte _____ with
increased colonocyte exposure to toxins, mutagens, procarcinogens and carcinogens and
increased risk for colorectal carcinoma.
apoptosis
106
oral antibiotic drugs also kill Lactobacilli
and Bifidobacteria, exerting impact on colon health, including
- colonocytes increased exposure to pathogens.
- incomplete fermentation of
dietary fiber decreases butyrate production and intracolonocyte acetyl CoA concentration and
energy status.
- increased intestinal permeability
107
Wheat, onions, asparagus, chicory, banana and artichoke are common sources of prebiotic
________________.
fructans (fructooligosaccharides; FOS) and inulin.
108
_______ are specifically fermented to SCFA’s by Bifidobacteria and are not converted to lactic
acid and do not induce lactic acidosis. Supplementation (4 g/day) increases the
proportion of Bifidobacteria in the colon.
fructooligosaccharides; FOS
109
“non-digestible fermentable carbohydrates that encourage
beneficial change in the host’s microbial balance” (Jose Saavedra, M.D., Johns Hopkins
University School of Medicine)
“non-digestible food ingredients that
beneficially affect the host by selectively stimulating the growth and activity of one or more
bacterial species in the colon, thereby improving host health” (Allan Tschernia, M.D., Mt. Sinai
School of Medicine).
Prebiotics
110
“oral dietary supplements containing live microbes that
beneficially affect the host’s microbial balance” (Jose Saavedra, M.D., Johns Hopkins
University School of Medicine).
Probiotics
111
Successful reseeding with adherent probiotic
species requires at least ________ of daily ingestion of at least 10 billion colony forming units
(1010 CFU) per species. Successful reseedingmay not be possible in some patients, who will
require life-long daily supplementation.
6 months
112
Premature infants exhibit [decreased/increased] ability to 1) secrete gastric pepsin and lipase and pancreatic
trypsinogen, lipase, amylase and chymotrypsinogen, and 2) secrete enterocytes (ectoenzymes, enterokinase and lactase)
decreased
113
Most iron is transported in the blood via the plasma carrier:
a. heme.
b. erritin.
c. transferrin.
d. albumin.
c. transferrin.
114
A required prerequisite to the digestion of proteins is the HCl-dependent
process called:
a. hydrolysis.
b. evaporation.
c. denaturation.
d. distillation.
c. denaturation.
115
The true digestibility of dietary fatty acids is:
a. 65% to 75%.
b. 75% to 85%.
c. 85% to 95%.
d. > 95%.
d. > 95%.
116
An example of a digestive enzyme secreted from the brush border of microvilli
to help with digestion is:
a. sucrase
b. protease
c. amylase
d. hydrochlaoric acid
