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Flashcards in Pharmacology Deck (40)
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functions of membrane proteins

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


4 types of receptors

  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)


features of a receptor

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


features of enzymes

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


what is a receptor

protein molecule that receives chemical signal from outside cell


what is a ligand

molecule or drug that binds to receptor. 

2 types:

  • agonist and antagonist



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



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


method of action of aspirin

  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


two types of COX enzyme

  • 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


increasing selectivity of anti-inflammatory drugs

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


key groups of receptors

Ion channel, G-protein coupled receptor, enzymes


receptor for alcohol


  • ionotropic, membrane bound, ligand gated chloride channel


alcohol and GABA

  • 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


receptor for cannabis

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


receptor for aspirin and ibuprofen

COX-1 and COX-2


marijuana and cannabinoid receptor

  • 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


why is it called fluid mosaic model

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



structure of phospholipid

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


fatty acid chain of phospholipid

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


movement of phospholipids

  • 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'


what affects membrane fluidity

  1. temperature
  2. type of fatty acid
  3. presence of cholesterol


effect of temperature of membrane fluidity

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


effect of type of fatty acid on fluidity

  • 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


effect of cholesterol on fluidity at low temperature

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


effect of cholesterol on fluidity at high temperature

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



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



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


how are proteins attached to lipid bilayers

  • 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


channel proteins

  • 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