Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
77 Cards in this Set
- Front
- Back
|
Most carbohydrates of the diet are… |
large polysaccrides or disaccharides |
|
|
Process of separating poly/disaccharides |
hydrolysis |
|
|
Most fats in diet are… |
triglyccerides |
|
|
What are triglycerides composed of |
glycerol plus fatty acids |
|
|
3 major sources of carbohydrates |
sucrose, lactose, starches (others: amylose, glycogen, alcohol, lactic acid, pyruvic acid, pectins, dextrins, carbohydrate derivatives in measts) |
|
|
What enzymes does saliva contain |
ptyalin (alpha-amalase secreted by parotid glands); |
|
|
No more than what percent of food is hydrolyzed in the mouth |
5% |
|
|
How long can food continue digesting in stomach before mixing with gastric secretions |
1 hour |
|
|
What pH does salivary amalase become inactive |
4 |
|
|
how much starch is hydrolyzed before mixing with gastric secretions |
as much as 30-40% |
|
|
How long does it take for starches to be completely hydrolyze once entering duodenum |
15-30 minutes (pancreatic amalase is several times more powerful) |
|
|
What enzymes do the enterocytes lining villi of small intestine contain? |
lactase, sucrase, maltase, and alpha-dextrinase |
|
|
What makes up lactose |
glucose and galactose |
|
|
what makes up sucrose |
fructose and glucose |
|
|
How are monosaccrides absorbed |
fdirectly into portal blood |
|
|
monosaccride breakdown percents once digested |
glucose 80%, galactose and fructose each around 10% |
|
|
What secrets HCl |
parietal (oxyntic) cells (pH of 0.8 when first secreted, then 2-3 when mixed in stomach) |
|
|
Major constituent of intercellular CT of meat |
collagen; broken down by pepsin (must be broken down before other proteins an penetrate meat) |
|
|
Where does most digestion occur |
upper small intestine in duodenum and jejunum |
|
|
pancreatic enzymes that act on chyme entering duodenum |
trypsin, chymotrypsin, carboxypeptidase, proelastase |
|
|
what does carboxypeptidase do |
cleaves individual aas from carboxyl ends of polypeptides |
|
|
What do trypsin and chymotrypsin do |
split protein molecules into small polypeptides |
|
|
Most proteins get digested down to… |
dipeptides and tripeptides |
|
|
where are peptidases located |
brush border microvilli membranes |
|
|
Two types of peptidase enzymes that are especially important |
1) aminopolypeptidase 2) several dipeptidases (split remaining polypepetides into di and tri pieces) |
|
|
Where are di and tripeptides transported |
through microvillar membrane into interior of enterocyte |
|
|
Where are most peptides split into individual aas |
in cystol; they pass into blood once formed |
|
|
Fat digestion in stomach |
small amount by lingual lipase (from saliva); less than 10% fat digestion |
|
|
Where does emulsification begin |
in stomach with agitation to mix food/fat with products of digestion |
|
|
Most emulsification occurs where |
in duodenum with bile (bile salts plus lecithin) |
|
|
What is the purpose of bile |
emusification; reduces interfacial tension of fat and makes it soluble |
|
|
average diameter of fat after emulsification |
~1 um; 1000-fold increase in SA |
|
|
Most important enzymes for digesting triglycerides |
pancreatic lipase (enough released to digest everything it can reach in 1 minute); enterocytes also have lipase, not usually needed |
|
|
What transports fatty acids to prevent reversal of digestion |
bile salts (remove monoglycerides and free fatty acids) |
|
|
Bile salt micelle specs |
3-6 um with 20-40 molecules; ferries |
|
|
Cholesterol esters |
combination of cholesterol and one fatty acid molecule; most common dietary cholesterol |
|
|
quantity of fluid absorbed by intestines each day |
1.5 L from ingested fluid and 7 L of GI secretions |
|
|
How much fluid is absorbed in small intestines |
all but 1.5 L |
|
|
What substances can be absorbed through the stomach |
high lipid-soluble substances like alcohol and aspirin in small quantities |
|
|
folds that increase the suface area in small intestine |
valvulae conniventes; increase SA 3 fold |
|
|
where are the folds most developed |
duodenum and jejunum; protrude as much as 8 mm into lumen |
|
|
How far do villi project from suface of mucosa |
~1 mm; increase SA 10 fold |
|
|
how much do microvilli increase SA |
at least 20 fold |
|
|
Organization of villus |
1) vascular system to absorb 2) central lacteal |
|
|
daily absorption from small intestine |
several hundred grams carbs, 100+ grams fat, 50-100 grams aas, 50-100 grams ions, 7-8 L water |
|
|
absorption capacity of small intestine per day |
serveral kg of carbs, 500 g fats, 500-700 g proteins, 20+ L water |
|
|
What can the large intestine absorb |
additional water, ions, very few nutrients |
|
|
How is water transported |
entirely through diffusion |
|
|
Sodium absorption/use in body |
20-30 g secreted into intestine, 5-8 g eaten; must absorb 25-30 g (1/7 of all body sodium) |
|
|
What percent of intestinal sodium passes into feces |
less than 0.5%; important in absorbing sugars and aas |
|
|
Na+ in intestinal epithelial cells |
1) transported actively into paracellular spaces 2)Cl- atoms follow Na+ 3) Na+ concentration in cells low (50mEq/L) 4)Na+ concentration in chyme ~142 mEq/L 5) Na+ follows gradient into cells |
|
|
How does aldosterone affect Na+ |
within 1-3 hours of release, increases activation of enzyme and transport mechanisms for all aspects of Na+ absorption in intestinal epithelium |
|
|
Increased Na+ absorption causes… |
secondary increase in Cl- and water absorption (plus some other substances) |
|
|
Cl- ion absoprtion |
rapidly absorbed in upper small intestine; fixes the electronegativity in chyme/electropositivity in paracellular spaces created by Na+ |
|
|
Bicarb absorption in small intestine |
1) when Na+ absorbed, moderate amount of H+ secreted into lumen 2) H+ combine with bicarb to form H2CO3 3) dissociated into water and CO2 4) water stays in chyme, CO2 absorbed directly into blood and expired in lungs |
|
|
Bicarb secretion in ileum and large intestine |
epithelial cells secrete bicarb in exchange for Cl-; neutralizes acid products formed by bacteria |
|
|
Flow of water in large intestines |
young/immature epithelial cells secrete NaCl into lumen which is reabsorbed by older/mature epithelial cells |
|
|
How does cholera and other diarrheal bacteria cause their effect |
stimulate fold secretion/young epithelial cells so greatly, old cells can not absorb quickly enough |
|
|
What specifically causes oversecretion with cholera |
formation of excess cyclic adenosine monophosphate, which opens large numbers of Cl- channels |
|
|
How are Calcium ions absorbed |
actively by duodenum; controlled by PTH and vit D |
|
|
Monovalent vs divalent ion absorption |
monovalent ions absorbed with ease in great quantities, divalent absorbed in small amounts |
|
|
Glucose absorption |
sodium co-transport mechanism (secondary active transport); facilitated diffusion into blood from epithelial cells |
|
|
Galactose absoption |
almost same as glucose (secondary active transport with Na+) |
|
|
Fructose absorption |
facilitated diffusion all the way through intestinal epithelium; transport rate 1/2 of glucose and galactose |
|
|
peptide/aa absorption |
most through Na+ co-transport; a few only use facilitated diffusion; at least 5 types of transport proteins for aa and peptides have been found |
|
|
lipid absorption |
transported by micelles and are immediately absorbed into epithelial cell membrane |
|
|
How much fat can be absorbed without/with bile micelles |
40-50 % versus 97% |
|
|
What happens to lipids once in epitheial cytoplasm |
taken up by smooth ER and used to make new triglycerides which are released as chylomicrons into lymph and go to thoracic duct |
|
|
Why so some lipids absorb directly into portal blood |
short and some medium chain fatty acids are water soluble and absorbed directly |
|
|
How much chyme enters colon each day |
1500 mL; most absorption in proximal 1/2 of colon |
|
|
tight jxns in large vs small intestine |
much tighter in large intestine; prevents back-diffusion of ions |
|
|
What causes osmotic gradient for water absorption in large intestine |
absorption od Na+ and Cl- ions |
|
|
max absorption of colon |
5-8 L of fluid and electrolytes/day |
|
|
Fxn of bacteria in colon |
1) digest some cellulose 2) vit K, vit B12, thiamine, riboflavin production 3) flatus (CO2, H2, and methane) |
|
|
composition of feces |
3/4 water 1/4 solid matter |
|
|
Solid matter composition of feces |
30% dead baccteria, 10-20% fat, 10-20 organic matter, 2-3% protein, 30% undigested roughage |
|
|
What causes brown color of feces |
stercobilin and urobilin (derivatives of bilirubin) |
