Digestion and Absorption of Nutrients (carbs and proteins)

Question 1

What are the 2 steps of digestion of protein and carb polymers

Answer 1

1. Intraluminal hydrolysis
2. Membrane digestion

These digested molecules are absorbed by enterocytes

Question 2

What is intraluminal hydrolysis

Answer 2

Breakdown of macromolecules into smaller molecules in lumen of GASTROINTESTINAL TRACT, facilitated by enzymes secreted by pancreas stomach and small intestine.

Carbs -> monosaccharides (by amylases and disaccharidases)

Proteins -> Peptides and amino acids (Proteases, eg. Pepsin, trypsin)

Lipids -> Fatty acids and gycerol (lipases)

Question 3

What is membrane digestion

Answer 3

Final stage of digestion, at epithelial cells in brush border membrane of enterocytes.

Enzymes embedded in the brush border (Disaccharidases and peptidases) break down partially digested nutrients (oligosaccharides) into absorbable forms.

Disaccharides -> Monosaccharides
Small peptides -> Amino acids

Maltase, sucrase and isomaltase cleave internal and terminal alpha 1-4 links.
Sucrase splits sucrose into glucose + fructose
Isomaltase can also cleave 1-6 alpha links

Can be absorbed into blood stream

Question 4

What are dietary carbs? What are they?

Answer 4

Macronutrients providing energy. Must be digested because starches and disaccharides are not absorbed by small intestine.

Monosaccharides (5-10%)
Disaccharides (30-40%)
Polysaccharides (the rest idk)

Question 5

Try understand purpose of oligosaccharides

Question 6

Structures of glucose, fructose and galactose

Answer 6

Question 7

Structures of lactose, maltose and sucrose

Answer 7

Question 8

What is α-amylase

Answer 8

Digests starch and glycogen by HYDROLYSING α-1,4 glycosidic bonds

Produced in salivary glands and pancreas

Salivary amylase starts process of carb digestion, inactivated by high pH of acidic stomach

Pancreatic Amylase is induced by CCK and completes starch digestion.

Cannot act on terminal alpha 1-4 or 1-6 links

Question 9

What are disaccharidases

Answer 9

Enzymes in wall of brush border of small intestine that break down disaccharides into monosaccharides which will be ready for absorption.

Lactase : Lactose -> Glucose + Galactose
Sucrase : Sucrose -> Glucose + Fructose
Maltase : Maltose -> 2 Glucose

Question 10

How much carb digestion occurs in stomach?

Answer 10

None, pH of stomach inactivates activity of salivary α-amylase

Question 11

How are carbs uptaken and absorbed

Answer 11

Question 12

Understand clinical relevance of all that bs

Answer 13

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