119 Questions
What is the main function of enzymes in the digestion process?
To catalyze carbohydrates, lipids, and proteins
In which part of the gastrointestinal tract does the vast majority of absorption occur?
Small intestine
What is responsible for the final removal of electrolytes and water?
Colon
Which structure increases the surface area of the mucosa threefold?
Mucosal folds
What is the role of the capillary network in the villus?
To remove absorbed nutrients quickly
How much does the net increase in surface area occur due to the micrvilli?
20 folds
What is the primary driving force for water absorption in the small intestine?
Active transport of Na+ at the lumenal membrane
What is the role of bile salts in lipid digestion?
Emulsify lipid into small droplets in the duodenum
Which hormone increases Na+ absorption in the colon to conserve water and Na+ during dehydration?
Aldosterone
What is the primary mechanism for Ca++ absorption across the intestinal epithelial cell?
Active transport at the lumenal membrane
Which vitamin is primarily absorbed in the ileum?
Vitamin B12
What is the role of calbindin in Ca++ absorption?
Transporting Ca++ across the cell by primary active process
How are chylomicrons expelled from the intestinal epithelial cells?
Exocytosis
What promotes iron absorption in the small intestine?
Acidic pH in the stomach and vitamin C
How do phospholipids and cholesterol diffuse out of micelles across the gut wall?
By simple diffusion into the epithelial cell
What is the primary driving force for water absorption in the small intestine?
Active transport of Na+ at the lumenal membrane
What is absorbed mainly in the upper part of the small intestine (duodenum and jejunum)?
Fe++ and vitamin C
What is absorbed passively in small intestine but usually secreted in exchange for Na+ in colon?
K+
Which enzyme is responsible for the initial digestion of carbohydrates in the oral cavity?
Amylase
What is the primary function of pepsin in protein digestion?
Hydrolyzing large peptides into smaller polypeptides
How are di- and tri-peptides transported into the enterocyte for protein absorption?
Active transport with Na+ pump as a co-transporter
Which enzyme is responsible for the final hydrolysis of glucose polymers and disaccharides into monosaccharides?
Maltase
What is the role of bile in fat digestion and absorption?
Emulsifying lipids to aid in their digestion
Which molecule is responsible for solubilizing lipids and aiding in their digestion?
Bile salts
What happens to salivary alpha-amylase (ptyalin) in the stomach?
It is inactivated at acidic pH
How does glucose primarily enter the epithelial cells for absorption?
$Na^-$ linked carrier transport
Which enzyme is responsible for digesting 50-80% of starch in the small intestine?
\beta-Amylase
What is the primary function of smooth muscle cells of the muscularis mucosa in the intestines?
Wave villi in the lumen to facilitate absorption
How are small peptides transported into enterocytes for protein absorption?
Active transport with Na+ pump as a co-transporter
What is the total net increase in surface area due to the intestinal mucosal folds, villi, and microvilli?
600 folds
What is the primary function of the capillary network in the villus?
To maintain a concentration gradient between lumen and blood in capillaries
Where does the vast majority of absorption occur in the gastrointestinal tract?
Small intestine
What is the role of bile salts in lipid digestion?
Emulsify lipids to aid in their digestion
Which structure increases the absorptive surface area of the mucosa threefold?
Intestinal Mucosal Folds
What is responsible for the final removal of electrolytes and water in the gastrointestinal tract?
Colon
Which enzyme digests 50-80% of starch in the small intestine?
Ptyalin
What is the primary driving force for water absorption in the small intestine?
Increased osmotic pressure
How does fructose primarily enter the epithelial cells for absorption?
Passive diffusion
What is the primary role of bile salts in lipid digestion?
Solubilize lipids and aid in their digestion
What is responsible for the final removal of electrolytes and water?
Peptidases inside the cytosol
What is absorbed mainly in the upper part of the small intestine (duodenum and jejunum)?
Starch
What is the primary function of smooth muscle cells of the muscularis mucosa in the intestines?
Move folds to permit spreading of chyme
Which molecule is responsible for solubilizing lipids and aiding in their digestion?
Bile salts
What is absorbed passively in the small intestine but usually secreted in exchange for Na+ in colon?
Fructose
What is absorbed primarily in the upper part of the small intestine (duodenum and jejunum)?
Starch
What promotes iron absorption in the small intestine?
Bile salts
What is absorbed mainly in the upper part of the small intestine (duodenum and jejunum)?
Starch
What is the primary driving force for water absorption in the small intestine?
Active transport of sodium
What is the main function of enzymes in the digestion process?
To catalyze the hydrolysis of macromolecules into smaller molecules for absorption
Which hormone increases Na+ absorption in the colon to conserve water and Na+ during dehydration?
Aldosterone
How are phospholipids and cholesterol transported across the gut wall?
Via passive diffusion through the lumenal membrane
What is the role of calbindin in Ca++ absorption?
It transports Ca++ across the cell by primary active process
Which vitamin is primarily absorbed in the ileum?
Vitamin B12
What happens to salivary alpha-amylase (ptyalin) in the stomach?
It gets denatured and becomes inactive due to stomach acidity
What promotes iron absorption in the small intestine?
Acidic pH in the stomach and vitamin C
How does glucose primarily enter the epithelial cells for absorption?
Via active transport by glucose carriers
What is absorbed passively in small intestine but usually secreted in exchange for Na+ in colon?
Chloride (Cl-)
What is responsible for the final removal of electrolytes and water?
Lacteals
Which enzyme is responsible for digesting 50-80% of starch in the small intestine?
Amylase
The vast majority of absorption occurs in the colon.
False
The net increase in the surface area due to mucosal folds, villi, and microvilli is about 600 folds.
True
The lumenal surface of the epithelial cells has macrovilli, which increase surface area 20 folds.
False
The primary function of the capillary network in the villus is to add nutrients to the absorbed substances.
False
The small intestine has specialized structures to decrease the absorptive capacity by decreasing the absorptive surface area of the mucosa.
False
Most nutrients are absorbed before reaching the ileum.
True
Chylomicrons are expelled from the epithelial cells by endocytosis.
False
The conjugated bile acids are more hydrophobic than the sterol nucleus.
False
The primary driving force for water absorption in the small intestine is the active transport of Na+ at the basolateral membrane.
False
Iron absorption is mainly promoted by alkaline pH in the stomach and vitamin C.
False
Bile salts form micelles in an aqueous environment by orienting the hydrophobic portion toward the shell.
False
The absorption of electrolytes is greatest in the ileum and increases toward the duodenum.
False
The primary function of smooth muscle cells of the muscularis mucosa in the intestines is the absorption of lipids.
False
Bile salts are absorbed actively in the terminal ileum.
True
The effect of aldosterone mainly occurs in the small intestine to enhance Na+ absorption.
False
Vitamin B12 is primarily absorbed in the duodenum.
False
Iron stored in the epithelial cell is transported into the blood where it binds to ferritin as needed.
False
Phosphates, oxalates, and phytic acid promote iron absorption in the small intestine.
False
The final digestion of carbohydrates results in the formation of glucose, fructose, and galactose.
True
The enzyme ptyalin is inactivated in the acidic pH of the stomach.
True
Lactase is responsible for splitting maltose and other glucose polymers into glucose.
False
Galactose enters the epithelial cells using a carrier linked to Na+.
True
Protein digestion in the stomach is limited because the pepsin and HCl cannot attack the interior of the food mass.
True
Bile salts are secreted by the liver to act in the lumen of the intestine, aiding in the solubilization and digestion of lipids.
True
Amino acids are primarily transported into the enterocytes using a Na+ dependent carrier.
True
The activity of pepsin results in hydrolysis of about 20% of proteins that enter the stomach, converting them into peptones and smaller polypeptides.
True
Fructose enters into the epithelial cells by facilitated diffusion using a carrier not linked to Na+.
True
The process of carbohydrate digestion begins in the oral cavity with the enzyme ptyalin.
True
Small peptides are transported into enterocytes by a carrier mediated transport system, which depends upon the activity of Na+ pump to maintain a chemical gradient for Na+ across the lumenal membrane.
True
Bile solubilizes lipids and aids in their digestion by acting as an emulsifier to increase lipid surface area for digestion.
True
Most nutrients are absorbed before reaching the ileum.
True
The lumenal surface of the epithelial cells has microvilli, which increase surface area 20 folds.
False
Vitamin B12 is primarily absorbed in the duodenum.
False
Bile solubilizes lipids and aids in their digestion by acting as an emulsifier to increase lipid surface area for digestion.
True
The effect of aldosterone mainly occurs in the small intestine to enhance Na+ absorption.
False
The primary function of the capillary network in the villus is to add nutrients to the absorbed substances.
False
Ptyalin, a salivary alpha-amylase, has an optimum activity at acidic pH.
False
The process of carbohydrate digestion begins in the stomach.
False
Pepsin and HCl in the stomach can fully attack the interior of the food mass for protein digestion.
False
Bile salts are hydrophobic molecules that do not solubilize lipids in the lumen of the intestine.
False
Glucose primarily enters the epithelial cells for absorption using a carrier not linked to Na+.
False
The absorption of electrolytes is greatest in the duodenum and decreases toward the ileum.
False
Proteolytic enzymes of the pancreas include endopeptidases, but not exopeptidases.
False
Fructose primarily enters the epithelial cells for absorption using the same carrier as glucose and galactose.
False
Bile is not required for fat digestion and absorption.
False
Cellulose, a glucose polymer, is digestible by enzymes of the gut.
False
Chylomicrons are expelled from the epithelial cells by exocytosis, not endocytosis.
False
The final digestion of carbohydrates results in glucose only.
False
Chylomicrons are expelled from the epithelial cells by endocytosis.
False
Vitamin B12 is primarily absorbed in the duodenum.
False
Bile salts are absorbed actively in the terminal ileum.
True
The primary driving force for water absorption in the small intestine is the active transport of Na+ at the basolateral membrane.
True
The final digestion of carbohydrates results in the formation of glucose, fructose, and galactose.
False
Bile solubilizes lipids and aids in their digestion by acting as an emulsifier to increase lipid surface area for digestion.
True
The activity of pepsin results in hydrolysis of about 20% of proteins that enter the stomach, converting them into peptones and smaller polypeptides.
False
Lactase is responsible for splitting maltose and other glucose polymers into glucose.
False
Chylomicrons are expelled from the intestinal epithelial cells by endocytosis.
False
Protein digestion in the stomach is limited because the pepsin and HCl cannot attack the interior of the food mass.
True
What is absorbed passively in small intestine but usually secreted in exchange for Na+ in colon?
False
The detailed mechanisms of iron absorption are still unsettled.
True
Test your knowledge on the digestion process catalyzed by enzymes for carbohydrates, lipids, and proteins, as well as the absorption process by specialized epithelial cells in the gastrointestinal tract. This quiz covers important concepts related to the University of Jordan's Department of Physiology and Biochemistry, Dental, Pt III.
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