Podcast
Questions and Answers
What is digestion primarily defined as?
What is digestion primarily defined as?
Which type of carbohydrate does not require digestion?
Which type of carbohydrate does not require digestion?
Where does the digestion of carbohydrates begin?
Where does the digestion of carbohydrates begin?
What stops the action of salivary amylase in the stomach?
What stops the action of salivary amylase in the stomach?
Signup and view all the answers
Which enzyme is responsible for carbohydrate digestion in the mouth?
Which enzyme is responsible for carbohydrate digestion in the mouth?
Signup and view all the answers
What is the role of pancreatic amylase in carbohydrate digestion?
What is the role of pancreatic amylase in carbohydrate digestion?
Signup and view all the answers
What ion is required for the activation of salivary amylase?
What ion is required for the activation of salivary amylase?
Signup and view all the answers
What is the primary type of carbohydrate that undergoes digestion?
What is the primary type of carbohydrate that undergoes digestion?
Signup and view all the answers
Why can't humans digest cellulose?
Why can't humans digest cellulose?
Signup and view all the answers
What is the end product of carbohydrate digestion?
What is the end product of carbohydrate digestion?
Signup and view all the answers
What is necessary for the activity of pancreatic amylase?
What is necessary for the activity of pancreatic amylase?
Signup and view all the answers
Which mechanism is NOT responsible for the absorption of sugars?
Which mechanism is NOT responsible for the absorption of sugars?
Signup and view all the answers
What role does cellulose play in human digestion?
What role does cellulose play in human digestion?
Signup and view all the answers
Which of the following sugars is absorbed through active transport?
Which of the following sugars is absorbed through active transport?
Signup and view all the answers
Which statement about intestinal brush border enzymes is accurate?
Which statement about intestinal brush border enzymes is accurate?
Signup and view all the answers
What does active transport of glucose and galactose require?
What does active transport of glucose and galactose require?
Signup and view all the answers
What process involves the simultaneous transport of glucose and sodium into the cell?
What process involves the simultaneous transport of glucose and sodium into the cell?
Signup and view all the answers
What is the role of the sodium pump in glucose transport?
What is the role of the sodium pump in glucose transport?
Signup and view all the answers
What condition arises from a deficiency of the enzyme lactase?
What condition arises from a deficiency of the enzyme lactase?
Signup and view all the answers
What happens to lactose in the absence of lactase in the gut?
What happens to lactose in the absence of lactase in the gut?
Signup and view all the answers
Which glucose transporter is primarily known for its role in the uptake of glucose in various tissues?
Which glucose transporter is primarily known for its role in the uptake of glucose in various tissues?
Signup and view all the answers
What initiates the emulsification of lipids in the stomach?
What initiates the emulsification of lipids in the stomach?
Signup and view all the answers
Which lipase acts on short chain triglycerides in the stomach?
Which lipase acts on short chain triglycerides in the stomach?
Signup and view all the answers
Which of the following glucose transporters is NOT mentioned as being important for glucose uptake?
Which of the following glucose transporters is NOT mentioned as being important for glucose uptake?
Signup and view all the answers
What is the primary product of the action of lingual lipase on triglycerides?
What is the primary product of the action of lingual lipase on triglycerides?
Signup and view all the answers
Which enzyme is responsible for the hydrolysis of cholesteryl esters?
Which enzyme is responsible for the hydrolysis of cholesteryl esters?
Signup and view all the answers
What role do bile salts play in lipid digestion?
What role do bile salts play in lipid digestion?
Signup and view all the answers
Which end products result from the complete digestion of triglycerides by pancreatic lipase?
Which end products result from the complete digestion of triglycerides by pancreatic lipase?
Signup and view all the answers
What is the primary function of phospholipase A2 during lipid digestion?
What is the primary function of phospholipase A2 during lipid digestion?
Signup and view all the answers
What is the significance of emulsification in lipid digestion?
What is the significance of emulsification in lipid digestion?
Signup and view all the answers
How does Orlistat function in relation to lipid digestion?
How does Orlistat function in relation to lipid digestion?
Signup and view all the answers
Which of the following is NOT a major end product of triglyceride digestion?
Which of the following is NOT a major end product of triglyceride digestion?
Signup and view all the answers
What composes the structure of mixed micelles?
What composes the structure of mixed micelles?
Signup and view all the answers
Which type of fatty acids do not require bile salts for absorption?
Which type of fatty acids do not require bile salts for absorption?
Signup and view all the answers
Where are short and medium chain fatty acids absorbed into the bloodstream?
Where are short and medium chain fatty acids absorbed into the bloodstream?
Signup and view all the answers
What happens to absorbed free glycerol in the intestine?
What happens to absorbed free glycerol in the intestine?
Signup and view all the answers
What condition is characterized by the loss of lipids in the feces?
What condition is characterized by the loss of lipids in the feces?
Signup and view all the answers
What can cause bile salt deficiency?
What can cause bile salt deficiency?
Signup and view all the answers
What is the main outcome of pancreatic enzyme deficiency?
What is the main outcome of pancreatic enzyme deficiency?
Signup and view all the answers
What is the end product when long chain fatty acids combine with 2-MAG?
What is the end product when long chain fatty acids combine with 2-MAG?
Signup and view all the answers
Study Notes
Digestion and Absorption
- Digestion is the process of breaking down food into molecules small enough to be absorbed.
- Absorption is the process of moving nutrients from the gastrointestinal (GI) tract into the bloodstream.
- Transport is the process of moving nutrients throughout the body using the circulatory and lymph systems.
- Elimination is the excretion of undigested food through feces
Digestion of Carbohydrates
- Carbohydrates broken down include:
- Polysaccharides: starch, glycogen, and cellulose
- Disaccharides: sucrose, maltose, and lactose
- Monosaccharides: glucose and fructose
- Monosaccharides do not need digestion.
- Carbohydrate digestion begins in the mouth with the help of salivary amylase (ptyalin) which:
- Hydrolyzes (1-4) glycosidic bonds in starch and glycogen
- Produces dextrins and maltose
- Requires Cl- ions for activation and a pH of 6.7
- Digestive action stops in the stomach due to its high acidity, but resumes in the small intestine.
- The small intestine has two stages of carbohydrate digestion:
- Pancreatic Amylase: hydrolyzes dextrins to a mixture of maltose, isomaltose, and limit dextrin, requiring Cl- ions for activity with an optimal pH of 7.1
-
Intestinal Brush Border Enzymes: responsible for final carbohydrate digestion, including:
- Lactase: hydrolyzes lactose into glucose and galactose.
- Sucrase: hydrolyzes sucrose into glucose and fructose.
- Maltase: hydrolyzes maltose into two glucose molecules.
- Isomaltase: hydrolyzes isomaltose into two glucose molecules.
Why Cellulose is Not Digested by Humans?
- Cellulose is a polysaccharide found in plants containing (1-4) glycosidic bonds in its structure.
- Humans lack the enzyme needed to break these bonds.
- Cellulose provides fiber that aids in intestinal motility and stool softening.
Absorption of Carbohydrates
- The final products of carbohydrate digestion are glucose, fructose, and galactose.
- Three mechanisms are responsible for absorption of these sugars:
- Passive Diffusion: relies on concentration gradients between intestinal lumen and mucosal cells.
- Facilitated Diffusion: requires carrier proteins and is sensitive to concentration gradients.
-
Active Transport: requires energy, a transport protein, and sodium ions.
- Glucose and galactose are absorbed via this mechanism using a sodium-dependent glucose transporter (SGLT-1).
- This process is called cotransport or symport.
- Energy is provided by ATP-linked sodium pumps.
Glucose Transporters
- There are 7 important glucose transporters (GLUT-1 to GLUT-7) for uptake of glucose into specific cells.
- GLUT-2 is found in the intestines, liver, and kidneys, and is a critical transporter for glucose uptake.
- GLUT-5 is found in the intestines and transports fructose.
Disorders of Digestion and Absorption of Carbohydrates
-
Lactose Intolerance: deficiency of the enzyme lactase results in lactose accumulation in the gut.
- Lactase hydrolyzes lactose into glucose and galactose.
- Undigested lactose is fermented by bacteria in the large intestine, producing gases (H2 and CO2) and acids (acetic acid), causing:
- Abdominal cramps
- Flatulence
- Diarrhea
- Dehydration due to water drawn into the lumen
-
Causes of Lactose Intolerance:
- Congenital: present at birth
- Acquired: develops later in life (primary or secondary)
Digestion of Lipids
- Digestion begins in the stomach where heat liquidizes lipids.
-
Emulsification: dispersion of lipids into small droplets to reduce surface tension.
- This process is essential for lipid digestion.
- Emulsification is achieved by:
- Bile salts
- Peristaltic contractions
-
Enzymatic Action on Lipids:
- Lingual lipase and gastric lipase act on short-chain triglycerides (SCTs).
- Pancreatic lipase, cholesteryl esterase, and phospholipase-A2 are essential enzymes for lipid digestion.
- Pancreatic Lipase: hydrolyzes fatty acids in the 1 and 3 positions of triglycerides, producing 2-monoacylglycerol (2-MAG) and two free fatty acids.
- Cholesteryl Esterase: hydrolyzes cholesteryl esters into cholesterol and free fatty acids.
- Phospholipase-A2: hydrolyzes fatty acids from the 2-position of glycerophospholipids, producing lysophospholipids.
- Orlistat: an anti-obesity drug, inhibits gastric and pancreatic lipases, reducing fat absorption and weight loss.
Absorption of Lipids
-
Mixed Micelles: spherical particles with hydrophilic exteriors and hydrophobic interiors.
- Formed by free fatty acids, 2-MAG, free cholesterol, lysophospholipids, and bile salts.
- Help in absorbing lipids.
-
Absorption:
- All digested products passively diffuse into mucosal cells.
- Short and medium-chain fatty acids do not require bile salts for absorption.
- They are absorbed directly into intestinal cells and enter the portal blood.
- They are transported to the liver bound to serum albumin.
- Fat-Soluble Vitamins (A, D, E, and K): packaged in micelles and absorbed.
Synthesis of Lipids in Intestinal Cells
- Long-chain fatty acids are activated by thiokinase to fatty acyl CoA.
- Acyl CoA combines with 2-MAG to form triglycerides.
- Absorbed cholesterol and lysophospholipids are reactivated to form cholesteryl esters and phospholipids.
- Free glycerol released in intestinal lumen is not reutilized but passes directly to the portal vein.
- Glycerol-3-phosphate, formed from glucose within intestinal cells, can be used for triglyceride synthesis.
Abnormalities in Lipid Digestion and Absorption
-
Lipid Malabsorption: loss of lipid in the feces.
- Can lead to loss of fat-soluble vitamins and essential fatty acids.
- Occurs in conditions such as:
- Bile salt deficiency: liver disease or bile duct obstruction.
- Pancreatic enzyme deficiency: pancreatitis or cystic fibrosis.
- Defective chylomicron synthesis.
- Steatorrhea: condition characterized by lipid loss in feces.
Digestion of Proteins
- Whole proteins are not absorbed.
- Pepsinogen, secreted by the stomach, is activated by its own acid to become the active enzyme pepsin.
- Pancreatic enzymes further break down proteins into peptides.
- Intestinal brush border enzymes break down peptides into amino acids, which are then absorbed.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the processes of digestion and absorption of nutrients. This quiz covers key concepts of carbohydrate digestion, including the types of carbohydrates and the role of enzymes. Enhance your understanding of how food is broken down and absorbed in the body.
