GF - Nutrients & Drug absorption

Question 1

carbohydrates

Answer 1

Diet contains disaccharides and complex polymers (starch and sucrose)

All carbs are broken down into monosaccharides & absorbed in the small intestine

Question 2

What breaks down glucose polymers to disaccharides?

Answer 2

amylase

Question 3

What breaks down disaccharides to monosaccharides?

Answer 3

maltase, surcrase, lactose

Question 4

examples of glucose polymers

Answer 4

starch, glycogen

Question 5

disaccharides examples

Answer 5

Glucose + Glucose: Maltose
Glucose + Fructose: Sucrose
Glucose + Galactose: Lactose

Question 6

monosaccharides examples

Answer 6

Glucose, Fructose, Galactose

Question 7

name transporters that transport fructose, glucose and galactose through the intestinal fluid to the capillary:

Answer 7

SGLT2
GLUT5
GLUT2

Question 8

Decreased lactase activity is associated with a condition known as ______ __________

Answer 8

lactose intolerance

Question 9

what stops disaccharides from converting into monosaccharides?

Answer 9

Lactase

Question 10

What are proteins broken down into and where are they absorbed?

Answer 10

di/tri peptide & absorbed in small intestine

Question 11

Proteins > smaller peptides (what enzyme?)

Answer 11

endopeptidase

Question 12

smaller proteins > di/tri peptides. amino acids (what enzyme?)

Answer 12

exopeptidase

Question 13

transporters of protein that transports them into the intentinal fluid (aminoacids) and capillary (di/tri peptides)

Answer 13

a.a - sodium co-transporter

di/tri - H+- PepT

Question 14

Most lipids are __________ and must be emulsified to facilitate digestion in the aqueous environment of the intestine

Answer 14

hydrophobic

Question 15

how are micelles formed?

Answer 15

bile salts coat lipids to make emulsions

Question 16

describe micelles

Answer 16

small disks with bile salts,
phospholipids, fatty acids, cholesterol,
and mono- and diglycerides

Question 17

nutrient digestion step by step

Answer 17

1. micelles formed
2. lipase and colipase digest triclycerides

Question 18

Nucleic acid polymers (DNA & RNA) digest into ????? by pancreatic and intestinal enzymes and are absorbed via active transporters.

Answer 18

amino bases and monosaccharides

Question 19

The fat-soluble vitamins

Answer 19

A, D, E, and K; are absorbed in the small intestine along with fats.

Question 20

The water-soluble vitamins

Answer 20

C and most B vitamins; are absorbed by mediated transport.

Question 21

B12 (seafood, milk, meat)

Answer 21

intestinal transporter for B12 is found only in the ileum and recognizes B12 only when the vitamin is complexed with a protein called intrinsic factor, secreted by the same gastric parietal cells that secrete acid)

Question 22

Electrolytes

Answer 22

Sodium, potassium, chloride and water are absorbed through various pathways

paracellular diffusion

Question 23

Drug absorption: 1. passive diffusion

Answer 23

FACTORS::

a) Rate of diffusion
-surface area
-thickness of the membrane
-molecular size & lipid solubility of the drug (diffusion constant)
what is rate of diffusion moving from GI tract to blood

b) Concentration of drug [D]/amount transfer
Transfer rate
Residence time at membrane

Question 24

drug absorption: 2. active diffusion

Answer 24

REQUIRE carrier

Low lipid soluble (hydrophilic) drugs use transporters

Organic anion transporters (OATs)
Organic cation transporters (OCTs)

Question 25

What will cross lipid bilayers by PASSIVE DIFFUSION?

Answer 25

un-ionised drugs (weak acids or weak bases)

Question 26

Factors affecting ionisation

Answer 26

pH (i.e. concentration of H+ ions)
pKa of drug
(pH at which 50% of molecules are in each state)

Question 27

what is the pH i
mouth
stomach
SI

Answer 27

7.4
1.5
5.3

Question 28

factors influencing drug absorption

Answer 28

G.I. motility
G.I. secretions & enzymes
Drug-food/supplement interactions
Differences in luminal pH along the GI tract
Surface area per luminal volume
Blood perfusion
Presence of bile and mucus
The nature of epithelial membranes

Question 29

Advantages of G. I absorption (physiological)

Answer 29

Large surface area for passive diffusion
Range of pH environments promotes the uptake of weak acids/bases
Richly vascularised (high blood supply)
Long tract and long dwell time
Some active transport (e.g. Levodopa taken up by phenylalanine transporter)
Small intestine is a major site for drug absorption

Question 30

Kinetics of absorption (oral, intravenous, oral compromised)
How well us drug absorbed in body?

Answer 30

Bioavailability (F): measure of proportion of dose absorbed, compared to I. V. (same) dose

F= AUC of oral/AUC of I.V (for oral drug)

Time to peak (tmax): time required to reach maximum drug concentration in plasma (is a measure of rate of absorption)

tmax (oral)