Digestion + Absorption

Question 1

Transcellular

Answer 1

Across

Question 2

Paracellular

Answer 2

Between

Question 3

Extent of absorption in carb + protein v iron + calcium

Answer 3

> 98% v less due to regulation

Question 4

Surface area amplification

Answer 4

Villi x 10 , Microvilli x20

Question 5

Digestion of amino acids and small peptides

Answer 5

Pepsin in gastric juice + luminal phase in s.i. -> pancreatic enzymes

Question 6

Larger peptides are digested by

Answer 6

Brush border peptidases

Question 7

Amino acids are transported to brush border by

Answer 7

Na+ dependent transport (di + tri peptides by H+ dep)

Question 8

Amino acids are transported to blood by

Answer 8

Facilitated diffusion

Question 9

Polysaccharides are digested by

Answer 9

Luminal digestion by salivary + pancreatic amylase

Question 10

Glucose absorbed in

Answer 10

Jejunum via SGLT1 (Na+ dep) + Glut2 (diff)

Question 11

Galactose is transported into blood through

Answer 11

Basolateral membrane

Question 12

Fructose uptake

Answer 12

Glut5 and Glut2 at brush border + basolateral membrane

Question 13

Water uptake

Answer 13

9/L is absorbed -> SGLT1 also water transporter

Question 14

Electrolyte uptake methods

Answer 14

1. Upper S.I. : electrolytes + H2O
2. Na+/ H+ exchange at brush border -> HCO3- uptake
3. K+/ Cl- -> paracellular transport
4. Lower S.I. : Na+/ H+, Cl-/ HCO3- at brush border : NaCl uptake

Question 15

Calcium uptake

Answer 15

350 mg/ day

• Upper S.I. via specific channel in luminal membrane
• Small amounts may be absorbed passively -> bones + kidneys -> Ca2+ haemostasis

Question 16

In calcium deficiency,

Answer 16

Vit D. metabolite, calcitrol, released

Question 17

Colonic electrolyte + water absorption

Answer 17

1. Transcellular + paracellular secretion of K+, Cl- -> HCO3- secretion in lower ileum
2. Na+ uptake at brush border -> absorption of SFCA’s

Question 18

Importance of bacteria in digestion

Answer 18

1. Bulk of luminal content -> 10^15 m in colon
2. Ferment indigestible carbs to SCFA’s
3. Major anion in caloric contents -> colonocyte metabolism
4. Degrade bile acids, cholesterol, drugs, food additives