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MPharm 2 - PH2114 > Unit 2 - Biological barriers & ADME 1 > Flashcards

Unit 2 - Biological barriers & ADME 1 Flashcards

1
Q

Give five ways of transport across a biological barrier

A 
Passive transcellular
Passive paracellular
Vesicular
Efflux
Metabolism
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2
Q

What are tight junctions made from?

A

Proteins between two cells forming non-covalent bonds

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3
Q

What is passive transport limited by?

A

Availability of an electrochemical gradient and suitable drug physiochemical properties for permeability

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4
Q

What are solute carriers limited by?

A

Selectivity of transporter for chemical features of substrate and availability of electrochemical gradient

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5
Q

What are active efflux carriers limited by?

A

Selectivity of transporter for chemical features of substrate
- driven by primary energy source

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6
Q

What is vesicular movement important for?

A

Limited importance for small molecules
Important for proteins/peptides
- endocytosis
- transcytosis

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7
Q

What is metabolism limited by?

A

Selectivity of enzyme for chemical features of substrate

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8
Q

Give examples of types of epithelial barriers

A 
Simple squamous
- lung alveolar type I
Simple cuboidal
- lung alveolar type II
Simple columnar
- kidney proximal tubule
Stratified squamous
- buccal
- non-keratinised
- skin
- keratinised
Stratified cuboidal
- glands and ducts
Stratified columnar
Pseudostratified columnar
- conducting airways of lung
- intestine
- nasal cavitiesSimple squamous
- lung alveolar type I
Simple cuboidal
- lung alveolar type II
Simple columnar
- kidney proximal tubule
Stratified squamous
- buccal
- non-keratinised
- skin
- keratinised
Stratified cuboidal
- glands and ducts
Stratified columnar
Pseudostratified columnar
- conducting airways of lung
- intestine
- nasal cavities
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9
Q

Which type of molecules don’t readily partition into cell membranes?

A

Hydrophilic molecules

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10
Q

How do hydrophilic molecules cross epithelial barriers?

A

Paracellular transport

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11
Q

Which type of molecules permeate easily across cell membranes?

A

Hydrophobic molecules

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12
Q

How do hydrophobic molecules cross epithelial barriers?

A

Transcellular transport

- large surface area

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13
Q

Give some examples of types of capillary

A

Continuous capillaries
Fenestrated capillaries
Discontinuous capillaries

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14
Q

How do normal capillaries allow paracellular diffusion of small molecules?

A

Cell junctions are not tightly sealed

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15
Q

Which barrier is the exception to capillary endothelium cells not being tightly sealed?

A

Blood Brain Barrier

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16
Q

What is a continuous capillary?

A

Epithelial cells that are held together by tight junction with intercellular clefts to allow fluid passage

17
Q

What is a fenestrated capillary?

A

Perforated by fenestra bearing thin diaphragm

- glomerular capillaries

18
Q

What is a discontinuous capillary also known as?

A

Sinusoids

19
Q

What is a discontinued capillary?

A

Contains inter-endothelial gaps >100nm wide
Discontinuities in the basement membrane as well
- liver sinusoids
- movement of macrophages and large particles

20
Q

What molecular properties effect the process of how a molecule will cross a membrane (e.g partitioning, diffusion, stability within barrier)?

A

Steric; molecular size, volume, shape
Hydrophobicity; lipid/ water
Ionic properties; Hydrogen bonding potential, pKa

21
Q

What is solubility?

A

Property of a solid to dissolve in a liquid to form a homogenous solution
solubility depends on the:
- physical and chemical properties of the solute
- temperature
- pressure
- pH of solution

22
Q

What is permeability?

A

Property of a membrane to allow passage of a solute

  • permeability depends on the
  • physical and chemical properties of the solute
  • physical and chemical properties of the membrane
  • temperature
  • pH of solution
23
Q

What is partition coefficient, P?

A

Measure of the differential solubility between octanol/water for neutral compounds or where the compound exists in a single form

24
Q

What is partition coefficient, D?

A

Appropriate descriptor for ionisable compounds as it is a measure of the pH dependent differential solubility of all species in the octanol/water system

25
Q

What is LogD dependent on for ionisable compounds?

A

pH and pKa

- distribution of charged and uncharged forms will change

26
Q

What are the two types of superfamilies of transporters present in cell membranes?

A 
ATP-dependent Binding Cassette (ABC) binding proteins
Solute carriers (SLC)
27
Q

Give some examples of ATP-dependent Binding Cassette (ABC) binding proteins

A 
P-glycoprotein
- P-gp
Multidrug Resistant Proteins
- MRPs
Breast Cancer Resistance Protein
- BCRP
28
Q

Give some examples of Solute Carriers (SLC)

A 
Organic cation transporters
- OCTs
Organic cation/carnitine transporters
- OCTNs
Organic anion transporters
- OATs
Organic anion transporting polypeptides
- OATPs
Peptide transporters
- PEPT1
- PEPT2
Amino acid transporters
Monocarboxylate transporters
29
Q

google pka and ionisaion

A

ghg

30
Q

Where does P-glycoprotein expression increase in the apical (luminal) plasma membrane of small intestine enterocytes?

A

From proximal to distal regions of the small intestine

31
Q

What factors affect the impact of P-glycoprotein?

A

P-gp expression and affinity for a drug
- higher pull through membrane
Passive membrane flux
- bypass P-gp

32
Q

Where is P-glycoprotein constitutively expressed?

A

Blood Brain Barrier
Lung epithelium
Kidney
Liver

33
Q

Give some examples of where integral membrane proteins found

A

Plasma membrane
Mitochondria
Intracellular organelles

34
Q

What is a secondary active transporter?

A

Transporter protein couples the movement of an ion (typically Na+ or H+) down its electrochemical gradient to the uphill movement of another molecule or ion against a concentration/electrochemical gradient

35
Q

What is a symport carrier?

A

A cotransporter carrying 2 molecules in the same direction (either into or out of the cell)

36
Q

What is an antiport carrier?

A

A cotransporter carrying 2 molecules in different directions

MPharm 2 - PH2114 (32 decks)

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