Podcast
Questions and Answers
What is the direction of transport in active transport?
What is the direction of transport in active transport?
- Against the concentration gradient, but without energy
- In the same direction as the concentration gradient
- From a higher concentration to a lower one (correct)
- From a lower concentration to a higher one
What is the source of energy for active transport in glucose absorption?
What is the source of energy for active transport in glucose absorption?
- Sodium pump
- Breakdown of glucose
- Hydrolysis of ATP (correct)
- Glycogenesis
What is the role of sodium ions in active transport?
What is the role of sodium ions in active transport?
- To transport glucose down its concentration gradient
- To bind to the transport protein
- To transport glucose against its concentration gradient (correct)
- To provide energy for active transport
What is the condition characterized by the inability to digest lactose due to lactase deficiency?
What is the condition characterized by the inability to digest lactose due to lactase deficiency?
What is the characteristic of congenital lactose intolerance?
What is the characteristic of congenital lactose intolerance?
What is the site of glucose and galactose absorption?
What is the site of glucose and galactose absorption?
What type of bonds are cleaved during the digestion of lipids?
What type of bonds are cleaved during the digestion of lipids?
Which enzyme is responsible for digesting lipids in the stomach?
Which enzyme is responsible for digesting lipids in the stomach?
What is the pH range for the intestinal phase of protein digestion?
What is the pH range for the intestinal phase of protein digestion?
What is the primary function of lingual lipase?
What is the primary function of lingual lipase?
What type of amino acids are found at the carboxylic end?
What type of amino acids are found at the carboxylic end?
Which hormone stimulates the release of bile acid from the gallbladder?
Which hormone stimulates the release of bile acid from the gallbladder?
What is the function of microvilli?
What is the function of microvilli?
What is the name of the enzyme that digests COO end of proteins?
What is the name of the enzyme that digests COO end of proteins?
What is the main function of pancreatic juice?
What is the main function of pancreatic juice?
What happens to the pyloric part's contractility during the intestinal phase?
What happens to the pyloric part's contractility during the intestinal phase?
What is the primary function of trypsin?
What is the primary function of trypsin?
Which cell type secretes gastric lipase?
Which cell type secretes gastric lipase?
What is the primary ingested lipid form?
What is the primary ingested lipid form?
What is the primary function of gastric inhibitory polypeptide?
What is the primary function of gastric inhibitory polypeptide?
What is the main source of carbohydrates?
What is the main source of carbohydrates?
What is the process that occurs before lipids are digested in the small intestine?
What is the process that occurs before lipids are digested in the small intestine?
What is the universal fuel for human cells?
What is the universal fuel for human cells?
What is the primary function of the parasympathetic nervous system in digestion?
What is the primary function of the parasympathetic nervous system in digestion?
What is the primary site of carbohydrate digestion?
What is the primary site of carbohydrate digestion?
What is the condition where the immune system attacks the tissues when eating gluten?
What is the condition where the immune system attacks the tissues when eating gluten?
What is the function of salivary α-amylase in the mouth?
What is the function of salivary α-amylase in the mouth?
What happens to carbohydrate digestion in the stomach?
What happens to carbohydrate digestion in the stomach?
What is the result of α-amylase action on dietary starch in the mouth?
What is the result of α-amylase action on dietary starch in the mouth?
What is the function of the enterogastric reflex in the digestion process?
What is the function of the enterogastric reflex in the digestion process?
What is the function of intestinal gastrin?
What is the function of intestinal gastrin?
What is the function of phospholipase A2 (PLA2)?
What is the function of phospholipase A2 (PLA2)?
What is the function of pancreatic lipase?
What is the function of pancreatic lipase?
What surrounds the small fat droplet?
What surrounds the small fat droplet?
What is the function of co-lipase?
What is the function of co-lipase?
What percentage of bile salts recycle through the enterohepatic cycle?
What percentage of bile salts recycle through the enterohepatic cycle?
What is the function of chemoreceptors at the duodenum?
What is the function of chemoreceptors at the duodenum?
What is the function of the lymphatic vessel?
What is the function of the lymphatic vessel?
Study Notes
Digestion and Absorption of Carbohydrates
- Carbohydrates are the major source of energy for humans
- Glucose is the universal fuel for human cells
- The principal sites of carbohydrate digestion are the mouth and small intestine
- Dietary carbohydrates consist of:
- Polysaccharides (starch, glycogen, and cellulose)
- Disaccharides (sucrose, maltose, and lactose)
- Monosaccharides (glucose and fructose)
- Monosaccharides do not require digestion prior to absorption, whereas disaccharides and polysaccharides must be hydrolyzed to simple sugars before absorption
- Digestion in the mouth:
- Salivary glands secrete α-amylase (ptyalin), which initiates the hydrolysis of starch
- α-amylase breaks some α-(1 → 4) bonds, hydrolyzing starch into dextrins
- Digestion in the stomach:
- Carbohydrate digestion temporarily halts in the stomach due to the high acidity that inactivates salivary α-amylase
- Active transport:
- The transport of glucose and galactose across the brush-border membrane of mucosal cells occurs by an active transport process that requires energy
- Sodium-dependent glucose transporter (SGLT-1) binds both glucose and Na+ at separate sites and transports them through the plasma membrane of the intestinal cell
Digestion and Absorption of Proteins
- Proteins are hydrolyzed into smaller peptides and amino acids through the action of various enzymes
- Proteolytic enzymes are produced in the stomach and small intestine
- Digestion in the stomach:
- Gastric amylase and gastric lipase hydrolyze carbohydrates and lipids, respectively
- Digestion in the small intestine:
- Pancreatic juice containing proteases (trypsin, chymotrypsin, and carboxypeptidases) and amylase hydrolyze proteins and carbohydrates, respectively
- Brush-border enzymes (peptidases and carbohydrases) further hydrolyze peptides and sugars
Digestion and Absorption of Lipids
- Dietary lipids consist of triacylglycerols (TAG), cholesterol esters, and phospholipids
- Digestion of lipids occurs mainly in the small intestine
- Emulsification of lipids by bile salts and phospholipids enhances the surface area for enzymatic digestion
- Pancreatic lipase hydrolyzes TAG into fatty acids and glycerol
- Colipase binds to lipase and substrate, enhancing enzymatic activity
- The products of lipid digestion are absorbed into the intestinal cells and re-esterified into TAG, which are then transported to the lymphatic system as chylomicrons
Regulation of Digestion and Absorption
- The digestive process is regulated by hormones and nervous system signals
- The enteric nervous system (ENS) and the central nervous system (CNS) interact to regulate digestion and absorption
- Hormones such as gastrin, cholecystokinin (CCK), secretin, and gastric inhibitory peptide (GIP) play key roles in regulating digestive processes
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Description
This quiz covers the physiological processes involved in digestion, including the cephalic, gastric, and intestinal phases, and their effects on stomach emptying.
