GI Digestion and Absorption

Question 1

What does digestion entail?

Answer 1

Decreasing size (all of the gut)

Question 2

What does absorption entail?

Answer 2

Passing nutrients to cells (small intestine)

Question 3

Where does absorption of lipids occur?

Answer 3

At the level of the brush border
Top: digestion
Bottom: defense mechanism

Question 4

What causes the defense mechanism for absorption to change?

Answer 4

Age: # of cells reduce and rate of regeneration decreases

Question 5

Methods of transport

Answer 5

Simple diffusion
Active diffusion
Facilitated diffusion
Pinocytosis

Question 6

Types of Digestion

Answer 6

Luminal (cavities)
Membrane (contact)

Question 7

Luminal Digestion

Answer 7

Digestive enzymes
Sources: mouth, stomach (least impt.), intestinal/ pancreatic (most impt.)

Question 8

Membrane digestion

Answer 8

Hydrolytic enzymes
Source: apical membrane of enterocytes

Question 9

What are the 3 types of nutrients?

Answer 9

Carbs
Proteins
Fats

Question 10

What is the end product of the digestion of carbs?

Answer 10

Glucose, fructose and galactose

Question 11

Digestion process of carbs

Answer 11

1. Starch at luminal digestion
2. Amalayse converted starch into carbs
   3.Carbs turned into sugars at membrane digestion

Question 12

Which carbs are digested?

Answer 12

1. Trehalose –> trehalase –> glucose
2. Lactose –> lactase –> glucose and galactose
3. Sucrose –> sucrase –> glucose and fructose

Question 13

What does the absorption of carbs involve?

Answer 13

Enterocytes with special carries for molecules

Question 14

What are the special carriers for carb absorption?

Answer 14

GLUT-5: fructose
SGLT-1: Glucose and galactose
GLUT-2: fructose, glucose and galactose (carries to blood stream)

Question 15

T/F Newborns don’t have special carriers for absorotion

Answer 15

TRUE

Question 16

What is the end product for the digestion of proteins?

Answer 16

Amino Acids

Question 17

Luminal digestion of proteins

Answer 17

Endopeptidases (eats inside of protein molecule)
Exopeptidase (eats out)

Question 18

Absorption of proteins

Answer 18

Free amino acids, di- and tripeptides (simple diffusion)
Large proteins: pinocytosis (decreases with age)

Question 19

What are the end products of the digestion of lipids?

Answer 19

Cholesterol, free fatty acids, monoglycerides, glycerol

Question 20

Steps of fat digestion

Answer 20

1. Gut motility creates fat droplet formation
2. Hydrolysis allows enzymes to work
3. Emulsification by bile salts/ phospholipids (prevents aggregation of lipid droplets)
4. Micelle formation (water soluble, no glycerol)

Question 21

How are micelles formed?

Answer 21

Water soluble molecule formed by
1. Bile Acid
2. Cholesterol OR Fatty Acid OR Monoglyceride
Bile salts will take FFA–> bind them from Micelle –> transport (adding charge onto a fat)

Question 22

Steps of lipid absorption

Answer 22

1. Micelle formation
2. Chylomicrons formation

Question 23

Chylomicrons formation

Answer 23

Mostly from long chain FA
Short and medium chain FA
Absorbed directly in the blood
(lacteals)

Question 24

Cholesterol

Answer 24

95% reabsorbed and 5% feces (intestinal/ bile)
Blood vessels are carriers

Question 25

Good and bad cholesterol

Answer 25

Good cholesterol: High density lipoproteins
Bad cholesterol: (low density lipoproteins)