Membranes Biochemistry

Question 1

What is meningitis?

Answer 1

Infection of meninges of the brain

Usually due to vital/bacterial infection

Question 2

What are the meninges?

Answer 2

Membranes that cover brain neuronal tissue

Question 3

Why are the meninges important?

Answer 3

Closely associated with blood brain barrier

Question 4

What is the blood brain barrier?

Answer 4

Selectively permeable membrane that regulates passage of small + large molecules into microenvironment of neurons of brain

Question 5

What are all the blood brain barriers?

Answer 5

Blood-retina barrier
Blood-spinal cord barrier
Blood-cerebrospinal fluid barrier
Arachnoid barrier 
Blood-brain barrier

Question 6

What type of barrier is the blood-brain barrier?

Answer 6

Physical barrier to molecule penetration into brain

Question 7

What is able to cross the BBB?

Answer 7

Pain killers (analgesics)
Anaesthetics
Antibiotics

Question 8

What doesn’t cross the BBB?

Answer 8

Antihistamines
Chemotherapy drugs
Drugs that cause vomiting + nausea

Question 9

What is the most important membrane?

Answer 9

GI tract

Question 10

Why is GI tract most important membrane?

Answer 10

Drug molecules need to be absorbed so they enter systemic circulation

Question 11

What happens when a patient takes a tablet?

Answer 11

Tablet enters stomach + dissolves
Absorbed in intestines
Enters circulation
Reaches action site

Question 12

What must the drug be to be absorbed?

Answer 12

Drug must be in reasonable soluble form

Question 13

What happens if a drug fails to be H2O soluble?

Answer 13

Cannot be absorbed from small intestine into systemic circulation
= therapeutic failure

Question 14

Why may a drug be H2O insoluble?

Answer 14

Tablet may not disintegrate (formulation problem)
Drug formulated in tablet granules = H2O insoluble

Question 15

What factors effect drug solubility of drugs?

Answer 15

Several polar groups - OH
Able to dissociate - eg. COOH
Poor electrolyte

Question 16

Why is having polar groups important for drug solubility?

Answer 16

Greater H bonding

= increases H2O solubility

Question 17

Why is being able to dissociate important for drug solubility?

Answer 17

Create proton + negative drug ion

Question 18

When are drugs poor electrolytes?

Answer 18

DO NOT dissociate readily

Question 19

What are examples of weak electrolytes?

Answer 19

Acetic acid
Ammonium
Phosphoric acid
Carbonic acid
GOOD SOLUBILITY BUT POOR DISSOCIATION

Question 20

Describe small intestine

Answer 20

Villi
Supplied with blood
Receive lymph supply
Rudimentary nerve supply

Question 21

What is the gut wall structure?

Answer 21

Mucous coat
Submucous coat
Muscular coat
Serous coat

Question 22

Describe mucous coat

Answer 22

Surface epithelium with glands
Loose fibrous tissue with capillaries + lymphatic vessels
Muscularis mucosae
Lymphatic tissue

Question 23

What is villi linked to?

Answer 23

Epidermis

Question 24

What does epidermal cells have?

Answer 24

Small finger like protuberances

= increase SA for absorption

Question 25

What is structure of cell membrane?

Answer 25

Phospholipid bi-layer

Question 26

What is structure of phospholipid bi-layer?

Answer 26

H2O soluble polar head = outside | Fatty acid chain = inside

Question 27

What drug property factors affect absorption of drugs?

Answer 27

Lipid/H2O solubility Molecular size Degree of ionisation Chemical structure

Question 28

How do drugs pass through cell membrane?

Answer 28

Passive diffusion

Question 29

What do drugs need to be to penetrate cell membrane?

Answer 29

Slightly hydrophilic to penetrate hydrophilic head | Slightly lipophilic to penetrate lipophilic head

Question 30

Why is paracetamol more likely to pass through cell membrane compared to Rifampicin?

Answer 30

``` Paracetamol = small Rifampicin = large ```

Question 31

What makes a drug more likely to pass through cell membrane?

Answer 31

Contain functional groups that donate or accept H+

Question 32

What does ionised form of a drug attract?

Answer 32

H2O = H2O soluble

Question 33

When is ionised form of a drug useful?

Answer 33

Enter hydrophilic area of membrane

Question 34

What happens when ionised form of a drug enters fatty acid section of membrane?

Answer 34

Ionisation reverses = drug becomes fat soluble

Question 35

What are the physical properties of membrane that affect drug absorption?

Answer 35

SA Thickness Conc gradient ^^^FICK'S LAW ^^^

Question 36

What happens in filtration?

Answer 36

Drug molecules pass through pore in membrane Dissolved in bloodstream Under increased pressure

Question 37

How does drug molecule pass through pore of membrane?

Answer 37

Force via dynamic pressure through pore

Question 38

What pressures are involved?

Answer 38

Hydrostatic | Osmotic

Question 39

What is the glomeruli?

Answer 39

Small sections of kidney

Question 40

What happens to blood vessels in kidney?

Answer 40

Blood supply under pressure = blood vessels narrow Increased blood pressure = H2O soluble drugs forced out of blood vessels

Question 41

What happens to micro blood vessels in kidney?

Answer 41

Fluid forced out of micro blood vessels THEN further forced through pores of membrane Cells form Bowman's capsule Fluid collects + passes to bladder

Question 42

Why do anti-inflammatory pain killers have an effect upon kidney filtration?

Answer 42

Cause narrowing of blood vessels = glomeruli vasoconstricts = pressure + vol of blood to glomeruli reduced = reduction in filtration

Question 43

Why is proportion of fluid reabsorbed by osmosis?

Answer 43

Blood vessels exert high osmotic pull

Question 44

Describe active transport across membrane

Answer 44

``` Transported by pore or protein Requires energy to open OR close pore Against conc gradient Energy from glucose + ATP Pumps = move molecules against conc gradient ```

Question 45

What is endocytosis?

Answer 45

Process of cell ingesting material by enveloping it in proportion of cell membrane

Question 46

What is phagocytosis?

Answer 46

Endocytosis of large particles

Question 47

What is pinocytosis?

Answer 47

Brings fluid containing dissolved substances

Question 48

What is receptor-mediated endocytosis?

Answer 48

Endocytosis by portion of cell membrane that contains receptors specific to certain substance