Module 1 Lec 2

Question 1

Define biotransformation

Answer 1

the body changes (transforms) substances into new chemicals (metabolits)

Question 2

What are the primary routes for absorption?

Answer 2

GI tract (ingestion)
respiratory tract (Inhalation)
skin (dermal)

Question 3

How and where can absorption take place in the GI tract?

Answer 3

Transport by passive diffusion
Absorption can take place anywhere from the mouth to rectum

Question 4

At what point will a compound be absorbed by the GI tract the most?

Answer 4

where the compound exists at it’s highest concentration and in it’s most lipid soluble form

Question 5

How does pH affect the absorption of toxic acids and bases?

Answer 5

when a toxin is in it’s less polar. nonionized form it’s more lipid soluble

weak aids more lipid soluble at low pH
weak bases more lipid soluble at high pH

Question 6

what are 6 factors that influence GI absorption?

Answer 6

Lipid solubility
pH
presence of transporters
size
actions of intestinal microflora, enzymes
presence of food / rate of passage

Question 7

what protein transporters efflux in GI tract and what uptake in GI tract?

Answer 7

ATP-binding cassette (ABC) efflux
solute carriers (SLC) uptake

Question 8

what is the main absorption site in the respiratory tract? why?

Answer 8

the alveoli due to the large surface area for respiration and small distance to blood capillaries

Question 9

what is the different pathway absorption for water-soluble and lipid-soluble gases?

Answer 9

water dissolve in mucus lining
lipid dissolve across alveolar membrane

Question 10

How do different particle sizes affect the respiratory tract?

Answer 10

larger impact the upper airways
smaller sizes deposit in the lower respiratory tract

Question 11

what 4 factors can compromise absorption through skin?

Answer 11

Compromised structure
hydration
increased temperature / blood flow
solubility of toxicant

Question 12

what 4 factors can compromise absorption through skin?

Answer 12

Compromised structure
hydration
increased temperature / blood flow
solubility of toxicant

Question 13

what 3 factors determine distribution rate?

Answer 13

blood flow
diffusion rate into organs
affinity of organ components to toxin

Question 14

what factors affect distribution?

Answer 14

properties of toxin
concentration gradient
cardiac output of tissues
detoxification reactions
tissue sensitivity
barriers inhibiting migration

Question 15

what happens when some of the ingested toxin is metabolized an excreted from the body?

Answer 15

more of the ingested toxin exits storage sites as it attempts to maintain an equilibrium with the body

Question 16

how does toxicity normally manifest?

Answer 16

manifests by the amount of toxin that is unbound

Question 17

why is albumin an important protein when exposed to a toxin?

Answer 17

has a high affinity to bind with toxin since it contains ~100 positive and negative binding sites

Question 18

What are some storage sites for toxins? what is unique to each?

Answer 18

liver / kidney - high binding capacity, high cardiac output, susceptible to repetitive exposure

Fat cells - vulnerable to highly lipophilic toxins, can be released during starvation, less toxic to obese persons

Bone - uptake on surface, vulnerable to metals

Question 19

what occurs during phase 1 and 2 biotransformation

Answer 19

Phase 1 - functional structure added

phase 2 - enzymatic reaction that conjugate the phase 1 product

Question 20

what organs are responsible for excretion?

Answer 20

Kidney (urine), liver (bile), lung (exhalation)

Question 21

what is the excretion functional unit for the kidney? what 3 processes are involved?

Answer 21

Unit: nephron
processes are:
- glomerular filtration
- tubular secretion
- tubular reabsorption

Question 22

what are the 2 processes involved in fecal execration?

Answer 22

biliary excretion (bile)
intestinal excretion (direct into the lumen of GI)

Question 23

what is the cycle where the liver reuptakes execrated substance from the GI tract?

Answer 23

the Enterohepatic circulation

Question 24

how are gases excreted from the lungs?

Answer 24

by passive diffusion that follows the concentration gradient