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Questions and Answers
What is the process by which glucose moves against its concentration gradient?
What is the process by which glucose moves against its concentration gradient?
Fructose is absorbed through the facilitated diffusion of GLUT2.
Fructose is absorbed through the facilitated diffusion of GLUT2.
False
What are the four major pathways of protein digestion-absorption?
What are the four major pathways of protein digestion-absorption?
- Luminal enzymes hydrolyse proteins to peptides and then to amino acids, 2) Luminal enzymes digest proteins to peptides, then brush border enzymes digest peptides to amino acids, 3) Luminal enzymes digest proteins to peptides which are taken up as oligopeptides, and 4) (not mentioned in the content)
The facilitated sugar transporter ______________________ is used for the exit of all three monosaccharides across the basolateral membrane.
The facilitated sugar transporter ______________________ is used for the exit of all three monosaccharides across the basolateral membrane.
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Match the following molecules with their primary transport mechanisms:
Match the following molecules with their primary transport mechanisms:
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What is the non-digestible polymer found in fruits, vegetables, and cereals?
What is the non-digestible polymer found in fruits, vegetables, and cereals?
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Salivary amylase continues to digest starch in the small intestine.
Salivary amylase continues to digest starch in the small intestine.
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What are the two steps involved in carbohydrate digestion?
What are the two steps involved in carbohydrate digestion?
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The ______________ transporter is responsible for glucose and galactose uptake at the apical membrane.
The ______________ transporter is responsible for glucose and galactose uptake at the apical membrane.
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Match the following enzymes with their functions:
Match the following enzymes with their functions:
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What is the product of starch hydrolysis in the small intestine?
What is the product of starch hydrolysis in the small intestine?
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Pancreatic alpha-amylase initiates starch digestion in the mouth.
Pancreatic alpha-amylase initiates starch digestion in the mouth.
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Glycogen is the storage form of carbohydrate in ______________.
Glycogen is the storage form of carbohydrate in ______________.
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What is the primary function of the stomach in the gastrointestinal system?
What is the primary function of the stomach in the gastrointestinal system?
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The large intestine is responsible for nutrient absorption.
The large intestine is responsible for nutrient absorption.
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What is the primary site for nutrient absorption in the gastrointestinal system?
What is the primary site for nutrient absorption in the gastrointestinal system?
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The pancreas secretes digestive enzymes and ____________________ to neutralise gastric acid.
The pancreas secretes digestive enzymes and ____________________ to neutralise gastric acid.
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Match the following structures with their respective functions in the gastrointestinal system:
Match the following structures with their respective functions in the gastrointestinal system:
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What type of carbohydrates can be directly absorbed by the small intestine?
What type of carbohydrates can be directly absorbed by the small intestine?
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The liver stores bile between meals.
The liver stores bile between meals.
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What is the role of bile acids in fat digestion?
What is the role of bile acids in fat digestion?
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Study Notes
Carbohydrate Digestion
- Carbohydrates require hydrolysis to monosaccharides before absorption
- Some polymers are digestible, others are not; non-digestible polymers are fiber
- Dietary fiber is non-digestible and found in fruits, vegetables, and cereals
- Glycogen is the storage form of carbohydrate in animals, equivalent to starch in plants
Carbohydrate Digestion Process
- Involves two steps: intraluminal hydrolysis and membrane digestion
- Intraluminal hydrolysis: starch to oligosaccharides by salivary and pancreatic enzymes
- Membrane digestion: oligosaccharides to monosaccharides by brush border disaccharidases
Intraluminal Hydrolysis
- Salivary and pancreatic acinar cells synthesize and secrete alpha-amylases
- Salivary amylase initiates starch digestion in the mouth, inactivated by gastric acid
- Pancreatic alpha-amylase completes starch digestion in the small intestine
- Products of starch hydrolysis are disaccharides, which require further digestion to produce absorbable monosaccharides
Membrane Digestion
- Involves hydrolysis of oligosaccharides to monosaccharides by brush border disaccharidases
- Three brush border oligosaccharidases with different hydrolytic functions: lactase, maltase, and sucrase-isomaltase
Carbohydrate Absorption
- Three monosaccharide products of carbohydrate digestion (glucose, galactose, and fructose) are absorbed by the small intestine in a two-step process
- Uptake across the apical membrane into the epithelial cell
- Coordinated exit across the basolateral membrane
- Sodium/glucose transporter 1 (SGLT1) responsible for glucose and galactose uptake at the apical membrane
Organisation of the Gastrointestinal System
- Gastrointestinal tract is a tube specialized along its length for sequential processing of food
- Series of hollow organs (mouth to anus) and accessory glands and organs that add secretions to the hollow organs
- Each hollow organ serves a specialized function, separated at key locations by sphincters
Organisation of the Gastrointestinal System (continued)
- Mouth and oropharynx: mechanical breakdown and lubrication of food, propels food into the oesophagus, initiates fat and carbohydrate metabolism
- Oesophagus: conduit to the stomach
- Stomach: temporary food storage, churns and secretes proteases and acid that facilitate digestion
- Small intestine: continues digestion, primary site for nutrient absorption
- Large intestine: reabsorbs fluids and electrolytes, stores faecal matter before expulsion
- Accessory glands: salivary glands, pancreas, liver
Pancreas and Liver
- Pancreas: secretes digestive enzymes, bicarbonate to neutralize gastric acid, and secretes into the duodenum
- Liver: bile secretion (stored in the gallbladder between meals), bile acids play a key role in fat digestion
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