Lecture 9 & 10: UNIT 2 Metabolism

Question 1

Enzymes that catalyze xenobiotic biotransformation are often called

Answer 1

drug-metabolizing enzymes.

Question 2

Xenobiotic biotransformation is the process

Answer 2

is a series of enzyme-catalyzed processes that alters the physiochemical properties of foreign chemicals (xenobiotics) from those that favour absorption across biological membranes (namely, lipophilicity) to those favouring elimination in urine or bile (namely, hydrophilicity)

Question 3

Absent xenobiotic biotransformation, many of the drugs in use today would have an

Answer 3

unacceptably long duration of action

Question 4

Xenobiotic biotransformation or drug metabolism is the process of

Answer 4

converting lipophilic (fat-soluble) chemicals, which are readily absorbed from the gastrointestinal tract and other sites, into hydrophilic (water-soluble) chemicals, which are readily excreted in urine or bile.

Question 5

Four categories enzyme systems

Answer 5

• Hydrolysis (eg, carboxylesterase)
• Reduction (eg, carbonyl reductase)
• Oxidation (eg, cytochrome P450 [CYP])
• Conjugation (eg, Uridine 5’-diphospho-glucuronosyltransferase)

Question 6

Individual xenobiotic-bio-transforming enzymes are located in

Answer 6

a single organelle, however, in such cases, the enzyme name generally refers to 2 or more enzymes, each with its own distinct subcellular location.

Question 7

xenobiotic biotransformation is accomplished by

Answer 7

a limited number of enzymes with broad substrate specificities

Question 8

Base on all the enzymes that perform biotransformation on xenobiotics, _____ ranks first.

Answer 8

CYP 450

Question 9

The highest presence of CYP 450 can be found in the

Answer 9

liver’s SER, but the enzymes are in all tissues.

Question 10

Cytochrome P450 (CYP 450) consists of how many gene families.

Answer 10

27 gene families.

Question 11

The three main gene families important in xenobiotic metabolism

Answer 11

CYP1, CYP2, and CYP3.

Question 12

Why is the CPY4 not best for xenobiotic metabolism

Answer 12

There also CYP4 but it works mostly of fat metabolism.

Question 13

How many families are within CYP 450?

Answer 13

There is one subfamily, i.e., CYP1A, CYP3A, CYP4A,

Question 14

How many subfamilies does CYP2 have?

Answer 14

CYP2 have five subfamilies A, B, C, D, and E.

Question 15

CYP 450 can be further subdivided into genes that

Answer 15

code for single enzyme proteins, such as CYP1A1 and CYP1A2.

Question 16

Subfamilies are denoted by capital

Answer 16

letters

Question 17

CYP3A4 means the

Answer 17

4th gene to be sequenced in the CYP3A subfamilies

Question 18

Proteins and genes are denoted

Answer 18

by Arabic numerals.

Question 19

A compound derived from the parent drug via metabolic pathways in

Answer 19

Phase I and/or Phase II.

Question 20

Metabolites are

Answer 20

the intermediate products of metabolic reactions catalyzed by various enzymes that naturally occur within cells.

Question 21

How does metabolism works?

Answer 21

Substances that enter the body are usually fat loving and are not ideal for excretion. They will be reabsorbed in the kidney or from the GI after biliary excretion.

Question 22

Metabolism (Biotransformation) makes the compounds more _____ compounds so they can be readily excreted.

Answer 22

polar

Question 23

Results of Metabolism

Answer 23

1. Parent molecule is converted into a more polar metabolite
2. Molecular weight/size increased
3. Facilitation of excretion from the body is increased

Question 24

Consequences of Metabolism

Answer 24

1. Biological half-life is decreased
2. Duration of exposure is reduced
3. Accumulation of compound in the body is avoided
4. Biological activity may change
5. Duration of biological activity may be affected

Question 25

Enzymes are responsible for

Answer 25

the conversion of compounds in the body and xenobiotics as well.

Question 26

Enzymes bind to compounds based on

Answer 26

structure and physiochemical properties

Question 27

Xenobiotics are not exclusively metabolized by

Answer 27

a specific enzymes.

Question 28

The organ responsible for the majority of xenobiotic transformation

Answer 28

is the liver.

Question 29

What oragn transports the majority of foreign compounds to the liver?

Answer 29

GI tract

Question 30

Why does the liver serve as a gateway to the rest of the body?

Answer 30

Because it converts endogenous compounds, it is ideal for converting xenobiotics.

Question 31

First-Pass effect can be so extensive that

Answer 31

none of the parent compound reaches the circulatory system.

Question 32

Enzymes that part take in biotransformation are usually found in:

Answer 32

1. Smooth endoplasmic reticulum (SER) (Most are found here)
2. Cytosol
3. Mitochondria

Question 33

Biotransformation is divided into how many phases?

Answer 33

Two phases