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91 Cards in this Set

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1. Catabolic reaction?
2. Anabolic rxn?
1. Breakdown of molecules to supply energy.
2. Synthesis of macromolecules.
Enzymatic hydrolysis accomplishes what?
accomplishes digestive breakdown.
What is vitamin?
Not a substrate, but serve a catalytic role as enzyme cofactor or prosthetic groups.
1 triglyceride + 2 H2O --------> 2 fatty acids + 1 monoglyceride. What enzyme causes this?
pancreatic lipase
polysaccharide + n H2O --------> disaccharide. What enzyme causes this reaction?
pancreatic amylase & ptyalin (from saliva)
Disaccharides --------> monosaccharide. What enzyme causes this reaction?
disaccharidases (sucrase, lactase, maltase)
polypeptide + n H2O ----->di/tripeptides. What enzyme causes this reaction?
gastric acidity/pepsin & pancreatic proteases.
di/tripeptides ------> amino acids. What enzyme causes this reaction?
peptidases.
3 characteristics of Gastrointestinal (GI) lumen.
1. Inside the gut; continuous with the space outside body.
2. Usable components of food are extracted.
3. Wastes are excreted as feces.
What is GI epithelium?
Innermost lining of lumen, attached to a basement membrane. Top (apical) surface faces into lumen.
What is tight junction of GI epithelium?
Side barrier of epithelium cells that separates body fluids from extracellular environment.
What is basolateral surface?
Surface opposite the lumen (sides and bottom of an epithelial cell).
2 layers of smooth muscle lining the gut.
Longitudinal layer (outer) & circular layer (inner)
5 characters that determine GI motility (rhythmic contraction)
1. Exhibits automaticity
2. Functional syncytium
3. Enteric nervous system
4. increased/decreased hormonal input
5. Parasympathetic nervous system (sphincters relax, allowing passage of food thru gut)
What is automaticity
Muscles contract periodically w/o external stimulation, thus creating a spontaneous depolarization.
Functional syncytium
one cell has action potential and contracts; the impulse spreads to neighboring cells.
2 purposes of GI motility.
1. Mixing food by disordered contractions of GI smooth muscle.
2. Movement of food down the gut by peristalsis, an orderly form of contraction.
1. Secretion
2. Excretion
1. Relases of useful substance by cells
2. Disposal of waste product
GI secretion is
1. stimulated by
2. inhibited by
1. food in the gut & parasympathetic nervous system
2. sympathetic stimulation
Exocrine glands
organized into sacs called acini that secrete products (digestive ENZYMES)into ducts, which empty into GI lumen.
Endocrine glands
ductless glands; secretions (HORMONES) picked up by capillaries and enter bloodstream.
GI Exocrine system consists of
liver, gallbladder, pancreas, and epithelial cells in gut wall
3 functions of epithelial cells of GI exocrine system.
1. gastric enzymes from stomach wall.
2. goblet cells secreting mucus and protects/lubricates the entire gut.
3. secretion of water to dissolve food.
GI Endocrine organs
pancreas and gut wall cells. Secretions picked up by nearby capillaries.
3 functions of mouth
1. fragmentation of food by masticulation (chewing).
2. lubrication by saliva.
3. food ---> bolus
saliva contains
1. salivary amylase that hydrolyzes starch to dissacharide.
2. lysozyme that attacks bact cell wall.
**No digestion of proteins/fats in mouth!**
upper & lower esophageal sphincters are
2 muscular rings that regulate food flow (peristalsis)
*lower sphincter: prevents reflux of chyme into esophagus.
3 functions of stomach
1. partial digestion of food
2. regulated release of food into small intestine.
3. destruction of microorgs.
3 roles of acidity of stomach
1. destruction of microorgs
2.acid-catalyzed hydrolysis of dietary proteins
3. pepsinogen ---> pepsin.
** pH~2, secretion of HCl by parietal cells.
Pepsin
Secreted by stomach that catalyzes proteolysis (protein breakdown).
Pepsinogen (inactive) ---> pepsin (active) by gastric acidity, not by an enzyme.
What is zymogen and how is it activated?
It's an inactive precursor and activated by proteolytic activation: cleavage of the protein at a specific site
ex: pepsinogen & trypsinogen
What is zymogen and how is it activated?
It's an inactive precursor and activated by proteolytic activation: cleavage of the protein at a specific site
ex: pepsinogen & trypsinogen
Chyme
a broken-down food mixed w/ gastric secretions
1. What is pyloric sphincter
2. What causes opening inhibition?
1. Prevents food into duodenum.
2. Excessive acidity in duodenum inhibits further stomach empying by contracting, which is done by nerves and hormones.
What inhibits the opening of pyloric sphincter?
Excessive acidity in duodenum inhibits further stomach empying by contracting, which is done by nerves and hormones.
What is the name of the hormone secreted by epithelial cells in duodenum?
cholecystokinin.
1. What is gastrin?
2. It's function?
1. Hormone secreted by G cells (stomach wall ep. cells).
2. Stimulates acid & pepsin secretion and gastric motility.
How is gastrin secretion stimulated?
Stimulated by
1. food in stomach
2. parasympathetic stimulation.
What is histamine?
What does blocking of histamine to a G cell receptor do?
1. Cofactor of acid stimulation by gastrin.
2. Less gastric acidity.
What does anti-histamine do?
More gastric acidity.
What is zymogen and how is it activated?
It's an inactive precursor and activated by proteolytic activation: cleavage of the protein at a specific site
ex: pepsinogen & trypsinogen
Chyme
a broken-down food mixed w/ gastric secretions
What is pyloric sphincter and what causes opening inhibition?
Prevents food into duodenum.
What inhibits the opening of pyloric sphincter?
Excessive acidity in duodenum inhibits further stomach empying by contracting, which is done by nerves and hormones.
What is the name of the hormone secreted by epithelial cells in duodenum?
cholecystokinin.
1. What is gastrin?
2. It's function?
1. Hormone secreted by G cells (stomach wall ep. cells).
2. Stimulates acid & pepsin secretion and gastric motility.
How is gastrin secretion stimulated?
Stimulated by
1. food in stomach
2. parasympathetic stimulation.
1. What is histamine?
2. What does blocking of histamine to a G cell receptor do?
1. Cofactor of acid stimulation by gastrin.
2. Less gastric acidity.
What does anti-histamine do?
More gastric acidity.
3 parts that make up small intestine (SI)
duodenum, jejunum, ileum.
(Digestion completed at jejunum.)
3 explanations why SI has large surface area.
1. length (10 ft)
2. villi - multicellular projections in the wall.
3. microvilli - microscopic foldings of SI ep. cell membranes.
Brush border
Lumenal surface of small intestine.
3 structures of villi and their description
1. capilaries - absorb dietary monosaccharides and amino acids (a.a.)
2. small lymphatic structure called lacteals, which absorb dietary fats.
3. Peyer's patches - a part of immune system; collections of lymphocytes at the villi.
Where do absorbed monosaccharides and a.a. go from villi?
capillaries --> veins --> hepatic portal veins (liver). Basically, blood from gut to liver.
Where to absorbed fats go from villi?
lacteals --> large lymphatic vessels --> thoracic duct --> bloodstream.
What 2 ducts empty into duodenum?
1. Pancreatic duct, which delivers exocrine secretions.
2. Bile duct, which delivers bile.
1. What is bile?
2. Where's it stored?
1. Contains bile acids made from liver cholesterol, which is absorbed & recycled.
2. It's stored in gallbladder
2 functions of bile
1. Vehicle for the disposal (excretion) of waste products by liver
2. Digestion of fats
Sphincter of Oddi
Where pancreatic duct & bile duct empty into.
Duodenal enterokinase
Activates pancreatic zymogen trpsinogen to trypsin.
**Duodenal enzyme
Trypsin
Enzyme that catalyzes protein ------> polypeptide reaction.
**differs from pepsin that it's active in basic envt. Secreted by pancreas and activated in SI
Brush border enzymes
Work on inside or surface of duodenum (NOT secreted). Hydrolyze smallest carbohydrates & protein ---> monosaccharide & a.a.
3 duodenal hormones
1. Cholecystokinin (CCK)
2. secretin
3. enterogastrone - decreases stomach emptying.
4 functions of Cholecystokinin (CCK)
1. secreted in response to fat.
2. causes pancreas to secrete digestive enzymes.
3. stimulates gallbladder contraaction (bile release)
4. decreases gastric motility.
3 roles of secretin
released in response to acid in duodenum.
2. causes pancreas to release high-pH buffer (HCO3- in H2O, very basic secretion)
3. Neutralizes HCl from stomach.
Duodenal pH must be
neutral or slightly basic for pancreatic enzyme to function.
2 functions of colon (muscular tube, 3-4 ft)
1. absorb water & minerals
2. form/store feces

Consists of cecum and rectum
Appendix
Composed of lymphatic tissue
2 parts of anal sphincter that controls defecation and their description
1. internal: smooth muscle, autonomic control
2. external: skeletal muscle, voluntary control
Gas
From undigested materials metabolized by colonic bacteria (normal flora).
2 importance of normal flora
1. colony competition: keep dangerous bact from proliferating.
2. supply of Vitamin K: essential for blood clotting.
3 enzymes of exocrine pancreas
1. pancreatic amylase
2. pancreatic lipase
3. Nucleases: hydrolyze dietary DNA/RNA
4. pancreatic proteases
Nervous system vs. pancreatic secretion
Sympathetic nervous system: decreased pancreatic secretion.
Parasympathetic: increased pan. secretion.
1. Islets of Langerhans
2. What hormones does each cells in it secrete?
1. small regions within the pancreas containing three types of cells: alpha, beta, & sigma.
2. Glucagon, insulin, and somatostatin
3 characteristics of glucagon (secreted by alpha cells)
1. secreted in response to low blood sugar.
2. stimulates liver to hydrolyze glycogen & release glucose into bloodstream.
3. stimulates adipocytes to release fats into bloodstream.
3 characteristics of insulin (by beta cells)
1. secreted in response to high blood sugar.
2. effect: opposite of glucagon.
3. stimulates removal of glucose from blood for storage as glycogen & fat.
Somatostatin (by sigma cells)
inhibits many digestive processes.
Body in response to high blood glucose does what?
releases insulin, which causes sugar removed and stored.
** diabetics: high blood pressure
** excess glucose destroys many physiological system.
Body in response to low blood glucose:
releases:
1. glucagon (polypeptide hormone from pancreas)
2. epinephrine (a.a. derivative from adrenal medulla)
3. cortisol (steroid from adrenal cortex)
3 hormones: raise blood glucose level.
1 hormone: lowers blood glucose level.
Why difference in number?
Low blood glucose level: immediately fatal.
High blood glucose level: harmless in short term.
5 functions of liver
1. secretes bile
2. stores sugar as glycogen
3. makes proteins from a.a.
4. renders toxins harmless
5. produces most of the blood proteins that circulate in plasma
2 functions of gallbladder
1. stores bile from liver until fatty meal's eaten
2. contracts in response to CCK and parasympathetic stimulation
monosaccharides and a.a. from SI to bloodstream
1. Na+ leaves the cell thru basolateral Na/K ATPase, creating a concentration gradient.
2. Monosac & a.a. taken into the ep. cell with Na+ (symport).
3. monosac & a.a. reach the bloodstream by facilitated diffusion down the gradient (uniport)
1. Chyme in duodenum causes:
2. Trypsin activates:
1. secretion of CCK and secretin.
2. proteases: polypeptide --> dipeptides
How's fat broken down? 4 steps.
1. Not broken down in stomach.
2. In duodenum CCK hormone released.
3. Lipase cannot digest clump of fats. CCK causes bile secretion; bile solubilizes fat.
4. Lipase works.
fat from SI to blood.
1. triglycerides ---> monoglyceride & fatty acid by pancreatic lipase.
2. into ep cells by simple diffusion.
3. Inside ep cells, converted back to triglycerides, which are packaged into chylomicrons.
4. chylomicrons enter lacteals (tiny lymphatic capillaries).
5. lacteals --> larger lymphatics --> thoracic duct --> large vein near heart.
Lipoprotein lipase
enzyme contained in adipose (fat cells) and liver tissues, which hydrolyzes chylomicron --> monoglycerides and free fatty acids.
2 types of vitamin
1. Fat soluble: require bile acids for solubilization & absorption. Stored in adipose tissue.
2. Water soluble: excreted in urine by kidneys.
4 Fat-soluble vitamins and their function.
A: visual pigment
D: stimulates Ca2+ absorption from the gut and deposition in bones.
E: Prevents oxidation of fats
K: Necessary for blood coagulation
5 types of water-soluble vitamin B
B1: for enzymatic decarboxylations
B2: made into FAD, electron transporter
B3: made into NAD
B6: protein & a.a. metabolism
B12: nucleotides --> deoxynucleotides
Other three water soluble vitamins
C: collagen formation; prevents scurvy.
biotin: CO2 transport
folate: transport of methylene groups, synthesis of purines & thymines, required for fetal nervous system development.