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BIOC192 1st half > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

functions of membrane proteins

A

intercellular joining, enzymatic activity, transport, cell-cell recog, anchorage, signal transduction

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2
Q

4 types of receptors

A
  1. Some receptors form a channel across the membrane (1)
  2. Some receptors transmit a signal across the membrane via G protein and 2nd messenger (2)
  3. Some receptors are membrane bound enzymes (3)
  4. Some receptors are intracellular so won’t be covered in this block (4)
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3
Q

features of a receptor

A
  • Several binding sites
  • Bind ligands
  • Releases ligand unchanged
  • Can be membrane bound or free in cytosol
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4
Q

features of enzymes

A
  • Generally one active site
  • Bind substrates
  • Changes substrate into product
  • Can be membrane-bound or free in cytosol
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5
Q

what is a receptor

A

protein molecule that receives chemical signal from outside cell

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6
Q

what is a ligand

A

molecule or drug that binds to receptor.

2 types:

  • agonist and antagonist
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7
Q

agonist

A

chemical capable of activating a receptor to induce a response - this is not always a positive response (increases action of a receptor)

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8
Q

antagonist

A

a drug that counteracts the effects of another drug or molecule (blocks action of a receptor)

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9
Q

method of action of aspirin

A
  1. Aspirin (ASA) binds the active site of the COX-2 enzyme
  2. This prevents Arachidonic Acid (AA) from binding
  3. No Prostaglandin (PG) is produced
  4. No inflammation
  5. Reduced pain
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10
Q

two types of COX enzyme

A
  • COX-2 - Converts arachidonic acid to prostaglandin causing inflammation and pain
  • COX-1 - Expressed in all cells, helps regulate the release of stomach acid. Therefore inhibition of this enzyme causes increase in stomach acid which results in stomach ulcers. At the same time, pain and inflammation in stomach decreases
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11
Q

increasing selectivity of anti-inflammatory drugs

A

“coxib” drugs like celecoxib specific to COX-2 have reduced side effects but still have anti-inflammatory effects

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12
Q

key groups of receptors

A

Ion channel, G-protein coupled receptor, enzymes

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13
Q

receptor for alcohol

A

GABAA​

  • ionotropic, membrane bound, ligand gated chloride channel
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14
Q

alcohol and GABA

A
  • GABA is inhibitory - slurred speech, memory loss and reduced inhibition
  • alcohol is an agonist
  • Receptor is ionotropic (ion channel)
  • Ethanol binds to GABAA ionotropic receptor, blocking GABA from binding
  • Agonist binding opens the channel and allows chloride ions (Cl-) into the cell
  • Alcohol changes AA sequence which affects secondary structure so subunit makeup of GABA receptor is changed
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15
Q

receptor for cannabis

A

cannabinoid receptor

  • G-Protein Coupled
  • both inhibitory and stimulatory effects simultaneously
  • High concentrations of CB1 in the brain
  • CB2 is found around the body e.g. spleen and pancreas
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16
Q

receptor for aspirin and ibuprofen

A

COX-1 and COX-2

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17
Q

marijuana and cannabinoid receptor

A
  • use a complex of proteins called G-proteins to send a signal from the membrane bound receptor to intracellular targets
  • Targets can be internal enzymes such as adenylate cyclase (forming cAMP) or can be other receptors such as an ion channels
  • Activation of CB1 causes appetite stimulation, euphoria, relaxation, anxiety and hallucinations
  • Cannabis is considered to be a very good analgesic (pain killer) but it has a range of side effects including hallucinations
18
Q

why is it called fluid mosaic model

A

Membrane is made up of many different components (Glycolipids, glycoproteins, phospholipids, cholesterol, integral proteins) which gives it a mosaic appearance, which can all move around each other in a fluid manner

19
Q

structure of phospholipid

A

Two hydrophobic fatty acids and a hydrophilic phosphate connect with glycerol to form phosphatidic acid

20
Q

fatty acid chain of phospholipid

A

can be saturated (no double bonds) or unsaturated (double bonds). even number of C’s and connected by ester bond

21
Q

movement of phospholipids

A
  • Move left to right and back and forth - this happens rapidly
  • Can switch sides of bilayer however this is slow and rare bc polar head has to move through hydrophobic tail region - ‘flip-flopping’
22
Q

what affects membrane fluidity

A
  1. temperature
  2. type of fatty acid
  3. presence of cholesterol
23
Q

effect of temperature of membrane fluidity

A

At higher temperatures, the phospholipids have more energy, and thus move around more AND the energy input breaks the Van der Waals interactions → phospholipids cannot pack close together → membrane fluidity increases

24
Q

effect of type of fatty acid on fluidity

A
  • Unsaturated fatty acids increase the fluidity of a membrane by preventing the phospholipids from packing close together because a double bond in a hydrocarbon tail kinks the fatty acid chain
  • Shorter fatty acid chains have fewer Van der Waals interactions between them, hence an overall weaker interaction between adjacent hydrocarbon tails compared to long ones, increasing the fluidity of the membrane
25
Q

effect of cholesterol on fluidity at low temperature

A

cholesterol is a bidirectional regulator - it prevents too close packaging of phospholipids when its hydrophobic rings interacts with/binds to adjacent hydrocarbon tails, partly immobilising those phospholipids → membrane fluidity is maintained at low temperatures and freezing (crystallization) is prevented

26
Q

effect of cholesterol on fluidity at high temperature

A

bidirectional regulator - many cholesterol molecules inserts themselves in the membrane (as there is more space between the phospholipids). The hydrophobic rings of the cholesterol interacts with/binds to adjacent hydrocarbon tails, partly immobilising those phospholipids → decrease membrane fluidity

27
Q

sphingolipids

A
  • type of membrane lipid
  • based on sphingosines (amino alcohols) instead of glycerol
  • abundant in myelin sheaths around nerve cells
28
Q

glycolipids

A

side chains attached by glycosidic (sugar-like) linkage (common in plants)

29
Q

how are proteins attached to lipid bilayers

A
  • Proteins can be attached to lipid bilayers by partially inserted proteins
  • Fatty acids can be used to anchor proteins in the membrane - post-translational addition of lipids
30
Q

channel proteins

A
  • when open, a channel is open to both the intracellular and extracellular space
  • Forms a polar core through which polar molecules can move down their concentration gradient
  • can open and close spontaneously or be regulated (“gated”)
  • rate of transport can approach rate of diffusion: 107 -108 molecules per second
  • e.g. aquaporin
31
Q

transporter proteins

A
  • transporters are open to either the intracellular or the extracellular space
  • binding induces a conformational change
  • rate of transport: 102 -103 molecules per second
  • transporters have several features in common with enzymes
  • Can only transport specific molecules
  • e.g. glucose transporter GLUT
32
Q

permeability coefficient

A

describes how easy and fast a molecule can move across a membrane

33
Q

transport of non-polar molecules e.g. O2 and CO2

A
  • Small, non-polar molecules, e.g. oxygen and carbon dioxide, are so small that they can fit through the spaces in the membrane
  • More hydrophobic = more permeable = moves through membrane faster
  • Larger concentration gradient = increase rate of transport for a non-polar molecule across a lipid bilayer
34
Q

non mediated

A

does not require protein

35
Q

mediated

A

requires protein (facilitated)

36
Q

passive

A

down a conc gradient

37
Q

active

A

requires an input of energy to move a molecule up its concentration gradient. Energy may come from the hydrolysis of ATP (primary active transport) or the co-transport of another molecule down its concentration gradient (secondary active transport)

38
Q

symport cotransport

A
  • both molecules move in the same direction.
  • Molecules should be moving in opposite gradient directions.
  • E.g. Na+ down a gradient which releases energy.
  • Glucose uses this energy to move up a gradient.
  • Both moving in the same direction
39
Q

antiport cotransport

A
  • the two molecules move in opposite directions.
  • e.g. Na+ down a gradient. Ca+ up a gradient.
  • Moving in opposite gradient directions
40
Q

Na+/K+ ATPase

A
  1. cytoplasmic Na+ binds to Na+/K+ pump
  2. Na+ binding stimulates phosphorylation by ATP
  3. phosphorylation causes conformational change in protein, expelling Na+ to outside
  4. extracellular K+ binds to protein triggering release of phosphate group
  5. loss of phosphate restores proteins original conformation
  6. K+ is released and Na+ sites are receptive again

BIOC192 1st half (6 decks)

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