Chapter 65: GI Digestion and Absorption (Discussion 9)

Question 1

Major Groupings of Nutrients

Answer 1

Carbohydrates, Proteins, Fats + MIcronutrients (e.g. vitamins)

Question 2

Major Groupings of Carbohydrates

Answer 2

Sucrose (sugar) Lactose (milk) Starches (big complex carbs)

Question 3

Cellulose

Answer 3

Undigestible form of complex carb found in plants (fibers)

Question 4

Carbohydrates Digestion (location)

Answer 4

Start in mouth Mainly in small intestine

Question 5

Carbohydrates Digestion (Mouth)

Answer 5

Salivary Amylase: Starch –> maltose + small carbohydrates

Question 6

Carbohydrates Digestion (Small Intestine)

Answer 6

Pancreatic Amylase: Starch –> small carbohydrates Enterocytes (intracellular/membrane enzymes): disaccharides –> monosaccharides

Question 7

Protein Digestion (location)

Answer 7

Stomach Small Intestine

Question 8

Protein Digestion (Stomach)

Answer 8

Pepsin: protein –> smaller peptide chains Responsible for breaking down collagen

Question 9

Protein Digestion (Small Intestine)

Answer 9

Trypsin/Chymotrypsin: peptides –> small peptides

Carboxypolypeptidase: peptides –> amino acids

Enterocytes peptidases: peptides –> di + tripeptides –> amino acids

Question 10

Fat Digestion (location)

Answer 10

Mouth Small Intestine Main form of fat = triglycerides

Question 11

Fat Digestion (Mouth)

Answer 11

Minimal Digestion/Not important Lingual lipase

Question 12

Fat Digestion (Small Intestine)

Answer 12

Bile + mechanical agitation –> emulsified fat globules Pancreatic lipase: triglyceride –> fatty acid + monoglyceride Enteric lipase: triglyceride –> fatty acid + monoglyceride

Question 13

Absorption Mechanism

Answer 13

Similar to kidney transport for movement of ions/water

• Na+/K+ pump on basolateral side provides Na+ gradient
• H₂O reabsorbed via osmosis (passively follows gradients)
• Cl- follows Na+
• HCO₃- reabsorbed by combining with H+ and diffusing in as H2O + CO2
• Aldosterone: increase H2O + NaCl absorption
• Different!: HCO₃- secreted in some portions to neutralize acid

Question 14

Stomach (little absorption)

Answer 14

Alcohol

Some drugs (aspirin)

Question 15

Small Intestine Absorption

Answer 15

Wall characteristics:

• Large surface area = large absorption capacity
  
  • Folds –> villi –> microvilli (brush border) = ~1000x increase in SA
• Pinocytosis to move substances at membrane –> cell body

Ions and H2O

• Ca++ reabsoprtion closely regulated by PTH
• Iron

AA’s & monosaccharides (mainly glucose) co-transported w/ Na+

Fat products diffuse across membrane

Question 16

Large Intestine Absorption

Answer 16

NaCl + H2O absorption

Secrete HCO₃- to neutralize acid from gut bacteria

Absorb vitamins produced by gut bacteria: Vitamin K and B are major ones