89 Questions
What enzyme is released from the salivary glands to begin the breakdown of starch?
Amylase
Why are proteolytic enzymes of the stomach and pancreas synthesized in inactive forms?
To prevent self-digestion of organs
Which enzyme is activated to pepsin within the low pH of the stomach for initiating protein digestion?
Pepsinogen
How are proteins broken down into amino acids during digestion?
By breaking peptide bonds between specific adjacent amino acids
What is the main role of proteolytic enzymes or proteases in protein digestion?
To release individual amino acids from proteins
Where are all proteolytic enzymes released from in their inactive forms?
Both the stomach and pancreas
What happens to chylomicrons when they reach blood capillary walls?
They enter the lacteals due to their size.
How are blobs of lipid separated into smaller micelles within the lumen of the small intestine?
By mechanical digestion with bile salts
What role do the endothelial cells of lacteals play in the absorption of chylomicrons?
Act as one-way valves
How are triglycerides handled within epithelial cells of the small intestine?
Reassembled and packed into chylomicrons
What is the fate of chylomicrons once they are formed within epithelial cells?
Absorbed into lacteals
In individuals with cystic fibrosis, what effect does the blocking of pancreatic ducts have on lipid digestion?
Reduced pancreatic lipase activity
What is the unifying property of lipids?
Hydrophobic
Which enzyme is responsible for limited digestion of triglycerides in the stomach?
Gastric lipase
What is the optimal pH range for lingual lipase?
4.5 - 5.4
Which of the following is NOT involved in the digestion of lipids in the stomach?
Bile salts
Which of the following is true about the breakdown of cholesterol?
Requires chemical digestion for absorption
Where does triglyceride digestion primarily continue?
In the small intestine
What inhibits the transport protein ferroportin in the GI tract?
Hepcidin
Which vitamins are categorized as fat-soluble vitamins?
Vitamin A, D, E, and K
How are fat-soluble vitamins absorbed into epithelial cells?
With lipids within micelles
What mechanism is used for the absorption of water-soluble vitamins?
Simple diffusion and active transport
Which vitamin requires receptor-mediated endocytosis for its absorption?
Vitamin B12
What is the glycoprotein released from parietal cells of the stomach that aids in the absorption of Vitamin B12?
Intrinsic factor
How is fluid balance maintained in the body when blood moves through capillaries?
Water leaves the blood to enter the interstitial and systemic cells
What is the primary function of electrolytes in the body's fluid balance?
Maintaining fluid balance
What happens to excess electrolytes consumed through diet?
They are eliminated in urine
How does diarrhea impact potassium (K+) levels in the body?
It leads to excessive loss of K+
What is the role of hepcidin in iron absorption?
It controls iron absorption by releasing from the liver
How does the small intestine contribute to electrolyte absorption?
It absorbs almost all of the electrolytes from the diet
Which enzyme is responsible for breaking the bond between two glucose molecules in maltose?
Maltase
What enzyme specifically digests sucrose into glucose and fructose?
Sucrase
Individuals lacking which enzyme are referred to as being lactose intolerant?
Lactase
What are the monosaccharides released from the enzymatic digestion of disaccharides?
Glucose, fructose, and galactose
Where are the monosaccharides absorbed into the blood during digestion?
Small intestine epithelial lining
Which enzyme converts fructose and galactose into glucose in the liver?
None of the above
What enzyme is responsible for the digestion of starch in the oral cavity?
Amylase
Which enzyme in the stomach is involved in limited digestion of triglycerides?
Gastric lipase
What enzyme in the small intestine is responsible for breaking down maltose into glucose?
Maltase
In lipid absorption, what specialized steps do hydrophobic molecules like lipids require?
Formation of micelles for absorption
Which enzyme is involved in the breakdown of lactose into glucose and galactose?
Lactase
Where does the activation of pancreatic enzymes like trypsin and chymotrypsin occur?
Duodenum
What is the main difference between micelles and chylomicrons?
Micelles contain digested triglycerides, whereas chylomicrons are formed within epithelial cells.
Where are chylomicrons formed?
In the Golgi apparatus of epithelial cells lining the small intestine
How do micelles transport lipids to the simple columnar epithelial lining?
By simple diffusion
What is the process by which fatty acids are reattached to monoglycerides to form triglycerides within epithelial cells?
Active transport
How are bile salts recovered from the GI tract back into the blood for recycling to the liver?
By active transport
What is a key function of chylomicrons once they are formed within epithelial cells?
To transport lipids to the simple columnar epithelial lining
What role does intrinsic factor play in the absorption of vitamin B12?
Forms a complex with vitamin B12 and transports it through the GI tract
Where do the B12–intrinsic factor complexes bind to receptors for absorption?
Distal ileum
What condition can result from a lack of intrinsic factor?
Pernicious anemia
How is the interaction between intrinsic factor and vitamin B12 described?
As a synergetic process
Which part of the gastrointestinal tract is essential for the absorption of the B12–intrinsic factor complexes?
Ileum
What enzyme is responsible for breaking the bond between the sugar and the nitrogenous base of a nucleoside?
Nucleosidase
Where are nucleic acid component building blocks absorbed?
Small intestine
What is the main site for both chemical digestion and absorption of nutrients?
Small intestine
What kind of digestion occurs within the stomach?
Both mechanical and chemical digestion
Which accessory digestive organ secretions are released into the duodenum to facilitate digestion in the small intestine?
Pancreatic secretions
Where do the final changes to chyme occur?
Large intestine
What is the enzyme responsible for breaking the bond between glucose subunits of oligosaccharides?
Dextrinase
Where does starch digestion continue within the small intestine?
Small Intestine
Which enzyme specifically digests sucrose to glucose and fructose?
Sucrase
What type of muscle contractions are weakest within the fundus of the stomach?
Smooth muscle contractions
Individuals with a lack of which enzyme are referred to as lactose intolerant?
Lactase
Which enzyme completes the breakdown of starch into individual glucose molecules in the small intestine?
Maltase
What disaccharides are digested by specific brush border enzymes in the small intestine?
Maltose and sucrose
Which enzyme breaks the bond between two glucose molecules in maltose?
Maltase
What are the monosaccharides released from the enzymatic digestion of disaccharides?
Glucose, fructose, and galactose
Which enzyme is produced and secreted from the pancreas into the small intestine for digestion?
Pancreatic amylase
Which type of enzymes are dextrinase, glucoamylase, and maltase?
Brush border enzymes
Where is the completion of starch breakdown accomplished in the small intestine?
Small Intestine lining
What is the main function of bile salts in the process of lipid digestion?
Facilitating the chemical digestion of triglycerides by pancreatic lipase
What role does lecithin play in the process of lipid digestion?
Facilitating the formation of micelles
After pancreatic lipase digests triglycerides into monoglycerides and fatty acids, where are these products absorbed?
Lacteal within the lamina propria
What happens to triglycerides after they are chemically digested by pancreatic lipase?
They are re-formed within epithelial cells
In lipid digestion, what is the function of chylomicrons formed within epithelial cells?
Transport lipids to lacteals
What is the final destination of chylomicrons after they are released from epithelial cells?
Lacteals in the lamina propria
What is the role of hydrochloric acid in the stomach during protein digestion?
Denatures proteins to facilitate their chemical breakdown
Why are proteolytic enzymes synthesized and released in their inactive forms?
To protect against auto-digestion of cells that produce them
What enzyme is primarily responsible for chemically digesting proteins into shorter strands of amino acids within the stomach?
Pepsin
What happens to protein digestion when chyme enters the small intestine?
Protein digestion is inhibited by the high pH of the small intestine
What is the primary function of trypsinogen, chymotrypsinogen, and procarboxypeptidase in protein digestion?
Continuing the digestion of proteins in inactive forms
What enzyme is activated in the stomach for initiating protein digestion due to the low pH?
Pepsin
Where does the majority of water absorption in the gastrointestinal tract occur?
Small intestine
What is the approximate daily amount of water that enters the small intestine?
8 liters
How much water is absorbed by the large intestine daily?
1.8 liters
By what process is water absorbed across the epithelial lining of the small and large intestines?
Osmosis
How much water, on average, is lost daily in feces after absorption in the digestive system?
200 mL
Which part of the gastrointestinal tract absorbs most of the water that enters it?
Jejunum
Test your knowledge on protein digestion enzymes and the activation process. Questions cover salivary enzymes for starch breakdown, proteolytic enzymes in stomach and pancreas, activation of pepsin, and more.
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