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Questions and Answers
What are the three main components that help the small intestine increase its surface area for absorption?
What are the three main components that help the small intestine increase its surface area for absorption?
Mucosal folds, villi, and microvilli.
Absorption of nutrients mostly takes place in the stomach.
Absorption of nutrients mostly takes place in the stomach.
False
What is the primary function of the esophagus?
What is the primary function of the esophagus?
Transporting food from the mouth to the stomach.
What are the two main types of carbohydrate digestion enzymes found in saliva?
What are the two main types of carbohydrate digestion enzymes found in saliva?
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What are the four enzymes found in the brush border that help digest sugars?
What are the four enzymes found in the brush border that help digest sugars?
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What are the two types of carrier-mediated transport systems involved in amino acid absorption?
What are the two types of carrier-mediated transport systems involved in amino acid absorption?
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What is the primary function of bile salts in lipid digestion?
What is the primary function of bile salts in lipid digestion?
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What is the main type of transport system used in the absorption of lipid components?
What is the main type of transport system used in the absorption of lipid components?
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Where is the main site for vitamin B12 absorption?
Where is the main site for vitamin B12 absorption?
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The digestion of carbohydrates begins once food reaches the stomach.
The digestion of carbohydrates begins once food reaches the stomach.
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The absorption of iron is primarily done by active transport.
The absorption of iron is primarily done by active transport.
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What is the name of the protein that binds to iron in the epithelial cells?
What is the name of the protein that binds to iron in the epithelial cells?
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What are the two main types of vitamins based on their solubility?
What are the two main types of vitamins based on their solubility?
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The absorption of water primarily occurs through active transport.
The absorption of water primarily occurs through active transport.
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Absorption of sodium electrolytes is primarily passive.
Absorption of sodium electrolytes is primarily passive.
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Match the following digestive enzymes with their primary action:
Match the following digestive enzymes with their primary action:
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The digestive process for lipids is similar to that of carbohydrates and proteins, involving active transport mechanisms.
The digestive process for lipids is similar to that of carbohydrates and proteins, involving active transport mechanisms.
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Chylomicrons are formed inside the intestinal epithelial cells.
Chylomicrons are formed inside the intestinal epithelial cells.
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The absorption of water is more efficient in the ileum compared to the duodenum.
The absorption of water is more efficient in the ileum compared to the duodenum.
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What hormone is primarily responsible for increasing sodium reabsorption during dehydration?
What hormone is primarily responsible for increasing sodium reabsorption during dehydration?
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What is the mechanism of chloride ion absorption in the upper part of the small intestine?
What is the mechanism of chloride ion absorption in the upper part of the small intestine?
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Calcium absorption is primarily passive throughout the entire intestinal tract.
Calcium absorption is primarily passive throughout the entire intestinal tract.
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What are the two main hormones that regulate calcium absorption?
What are the two main hormones that regulate calcium absorption?
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Ferrous iron (Fe++) is less soluble than ferric iron (Fe+++).
Ferrous iron (Fe++) is less soluble than ferric iron (Fe+++).
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What is the primary mechanism that prevents excess iron from entering the bloodstream?
What is the primary mechanism that prevents excess iron from entering the bloodstream?
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What are the two main categories of vitamins based on their absorption mechanisms?
What are the two main categories of vitamins based on their absorption mechanisms?
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Water-soluble vitamins are primarily absorbed passively.
Water-soluble vitamins are primarily absorbed passively.
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What is the specific factor required for the absorption of vitamin B12?
What is the specific factor required for the absorption of vitamin B12?
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Lipid-soluble vitamins are absorbed through the same mechanisms as lipids themselves.
Lipid-soluble vitamins are absorbed through the same mechanisms as lipids themselves.
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Study Notes
Digestion and Absorption
- Digestion involves enzymes breaking down carbohydrates, proteins, and lipids.
- Absorption is by specialized epithelial cells.
- Most absorption happens in the small intestine, some in the stomach, and none in the esophagus.
- The colon absorbs remaining water and electrolytes.
- The small intestine's structure increases nutrient absorption.
- Mucosal folds (Kerckring folds) triple surface area
- Villi increase surface area tenfold
- Microvilli on epithelial cells increase absorption 20 times, leading to a total surface area of about 600 folds.
Carbohydrate Digestion and Absorption
- Carbohydrates are ingested as starch, sucrose, lactose, and cellulose.
- Cellulose cannot be digested.
- Digestion starts in the mouth with salivary amylase (ptyalin).
- Salivary amylase breaks down 1-4 alpha-glycosidic bonds in starch.
- Pancreatic amylase further breaks down starch into maltose and maltotriose.
- Brush border enzymes (lactase, sucrase, maltase) hydrolyze disaccharides.
- Final products are glucose, fructose, and galactose, which can be absorbed.
Protein Digestion and Absorption
- Protein digestion begins in the stomach with pepsin and HCL.
- Pepsin and HCl break down peptide bonds, creating large polypeptides.
- Proteolytic enzymes (endopeptidases and exopeptidases) in the small intestine further break these down.
- Brush border enzymes (peptidases) break down peptides into oligopeptides and then amino acids.
- Di- and tripeptides are absorbed via a carrier-mediated transport system.
- Amino acids are absorbed through Na+-dependent carriers.
Lipid Digestion and Absorption
- Bile salts emulsify lipids, creating smaller droplets.
- Pancreatic lipase digests triglycerides into free fatty acids (FFAs) and monoglycerides.
- FFAs, monoglycerides, cholesterol, phospholipids, and bile salts combine to form micelles.
- These micelles diffuse into the epithelial cells.
- Inside the cells, FFAs and monoglycerides reform into triglycerides.
- Triglycerides combine with cholesterol and phospholipids to form chylomicrons.
- Chylomicrons are expelled from cells via exocytosis and enter lymphatic vessels.
- Glycerol and short-chain fatty acids are absorbed directly into capillaries.
Water and Electrolyte Absorption
- Water absorption is driven by sodium transport.
- Water follows sodium into the cells through tight junctions.
- Electrolytes (e.g., sodium, chloride, potassium) are actively absorbed in the small intestine and colon.
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Description
Test your knowledge on the processes of digestion and absorption, focusing on the roles of enzymes and the structures that enhance nutrient uptake in the digestive system. This quiz covers both the general digestion processes as well as specific carbohydrate digestion. Perfect for students of biology or health sciences.
