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MP221 Normal Function of the GI Tract > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

What are drugs ?

A

Molecules that interact with a biological system to produce a biological response.
Mostly small molecules, MW’s less than 600.
Not endogenous.

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2
Q

Can a drug ever be totally safe ?

A

No, no drug is safe. There has to be a balance between efficacy and toxicity.

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3
Q

What is drug safety dependent on ?

A

It is dependent on its therapeutic index/window and this varies for all drugs.

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4
Q

What is the therapeutic index/window ?

A

It dictates the effective dose of a drug that can be administered.
The wider the window, the more liberal the dosing can be and the narrower the window, the more closely monitored the dose must be.

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5
Q

What are biologics ?

A

These are larger drug molecules, e.g. antibodies and proteins as therapeutic agents.

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6
Q

What is a drug target ?

A

Usually a biomacromolecule involved in the biological process that is responsible for producing the symptoms or causing the illness.

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7
Q

What is a biomacromolecule ?

A

A receptor, enzyme, ion channel.

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8
Q

Why are drugs administered ?

A

To achieve a biological response that alleviates the symptoms or cause of an illness.

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9
Q

What does the drug molecule interact with ?

A

With the molecular target and produces a response that is clinically beneficial.

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10
Q

Where is the drug target ?

A

It is buried somewhere in a physiological system i.e. a patient.

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11
Q

Process of the drug reaching their target - step 1

A

The tablet is swallowed and enters the stomach.

The stomach is very acidic and so the drug is protected to survive this environment.

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12
Q

Process of the drug reaching their target - step 2

A

The drug moves from the stomach to the small intestine.

The small intestine has a large SA which allows a high rate of drug absorption.

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13
Q

Process of the drug reaching their target - step 3

A

The drug is absorbed across the lipid membrane of the GI tract and enters the bloodstream.
There is a competing process where reflux pumps will pump compounds that have been absorbed back out.
So the rate of absorption needs to be much faster than the rate of the drug being pumped out so that the drug can accumulate in the systemic circulation.

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14
Q

Process of the drug reaching their target - step 4

A

The drug moves into the systemic circulation and goes to the hepatic portal vein and directly to the liver.
The liver is the primary site of metabolites in the body.
The liver is full of enzymes that metabolise exogenous and foreign molecules in the body.
A lot of drugs can be lost in the first pass through the liver if they have not been properly designed.

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15
Q

Process of the drug reaching their target - step 5

A

The drug enters the systemic circulation and enters the blood flow of the body.

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16
Q

Process of the drug reaching their target - step 6

A

The dugs cross the lipophilic membranes to reach the actual site of action.

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17
Q

What is it that fives rise to the observed biological effects ?

A

The interaction between the drug and its target.

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18
Q

The key intermolecular interaction that promote associating between the drug and the amino acid target protein’s binding site

A

Hydrogen bonding, VDW/LDF, ionic/electrostatic, pi-pi bonding, dipole interactions.

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19
Q

The types of interactions available for any drug molecule is directly related to…

A

… the functional groups it contains.

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20
Q

What else is dictated but the functional groups present ?

A

Physiochemical properties like water solubility and membrane permeability.

21
Q

Types of functional groups

A

Phenyl groups, carboxylic acid, fluorine, tertiary butyl group, secondary aliphatic amine.

22
Q

There are three different alcohols each with…

A

… different properties and therefore form different interaction and have different pKa’s.
But they all form H bonding and potentially ionic bonds.

23
Q

What type of targets do drugs interact with ?

A

Amino acid based targets.

24
Q

What do proteins need in order to interact with and partner up with their target ?

A

The proteins need complementary features to allow partnering.

25
Q

How are amino acids grouped ?

A

Amino acids are grouped based on their physiochemical properties and the interactions they will be involved with.

26
Q

Types of amino acid groupings

A

Non-polar aliphatic side groups, aromatic side groups, polar uncharged side groups, charged side chains.

27
Q

Non-polar aliphatic side groups

A

Have non-polar lipophilic groups and are involved in short range VDW.

28
Q

Aromatic side groups

A

Involved in VDW and pi-pi bonds.

29
Q

Polar uncharged side groups

A

Mid-range H bonding reactions.

30
Q

Charged side chains

A

Involved in long range ionic bonds.

31
Q

What is it that gives the drug its binding properties ?

A

It is the relationship between the complementary functional groups/molecules.

32
Q

What is the difference between alpha helices and beta sheets ?

A

Whether they are inter or intra molecular hydrogen bonds between the structure.

33
Q

Why is the tertiary structure important ?

A

The tertiary structure enables the enzyme to perform its function and maintain the integrity of the active site where the catalysis is performed.

34
Q

The amino acids that border the active site produce…

A

… a particular 3D shape that maximises the interactions between the enzyme and the substrate, i.e. the enzyme is sculpted to the shape of the AA.

35
Q

What do these interactions ensure ?

A

They ensure that the substrate us held in the correct position for long enough so that the reaction can be catalysed.

36
Q

What type of structure do enzymes have ?

A

Enzymes have globular tertiary structures and have a surface which excludes small molecules from penetrating the interior.

37
Q

Properties of the active site

A

The active site is flexible and can expand and contract which allows molecules (substrates) in and the products out and the cycle continues.
This cycle is catalytic.
The enzyme is unchanged from before and after the reaction.
Forces the substrate into a transition-state compound which lowers the activation energy of the reaction taking place.

38
Q

Types of interactions between the amino acids and the substrates

A

Hydrogen bonds - directional and specific for H bonding groups on the substrate.
Short range VDW interactions - between the surface of the substrate and the surface of the active site.

39
Q

Which interaction is looser ?

A

VDW interactions are looser than H bonds.

40
Q

Flurbiprofen

A

Is a competitive inhibitor of the COX enzyme.
It binds in preference to AA and therefore blocks PG synthesis which reduces the inflammatory response.
Needs to have some structural resemblance so that it can match the 3D shape of the active site.

41
Q

What must be done in order for the drug to effectively compete with the substrate ?

A

The drug must form stronger interactions with the active site than the substrate so that the drug binds in preference to the substrate.

42
Q

What does it mean that the binding process is dynamic ?

A

This means that the molecules will associate and dissociate regularly.
Inhibitors need to stay in the active sit longer than the substrate to be effective.

43
Q

Aromatic rings have…

A

… better short-range interactions.

44
Q

Pharmacodynamics =

A

What the drug does to the body, i.e. the therapeutic effects of the drug, how it exerts its effects and how it interacts with the target.

45
Q

Small changes to the functional groups can change…

A

… the pharmacological action of a drug.

46
Q

Pharmacokinetics =

A

What the body does to the drug.
How the drug is distributed and absorbed in the body.
How long the drug stays in the body, i.e. metabolic rates etc.

47
Q

Changing a drug’s functional groups to modify the pharmacodynamic effects will also affect…

A

… the pharmacokinetic profile and vice versa.

48
Q

What do physiochemical properties facilitate ?

A

Absorption via oral administration.

49
Q

What can control metabolism and half-life ?

A

Modification of functional groups.

MP221 Normal Function of the GI Tract (13 decks)

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