1E Foundations 5 - Cell Biology - Plasma membrane Flashcards
Name the different types of phospholipids in the plasma membrane?
- Phosphatidylcholine (aka lecithin)
- Phosphatidylserine
- Phosphatidylinositol
Components of the plasma membrane?
- Phospholipid bilayer
- Proteins (more protein than phospholipids)
- Glycoprotein
- Glycolipids
- Sphingolipids
- Cholesterol (15% of plasma membrane)
Tyrosine kinase receptors function?
Transfer a phosphate group (phosphorylate) from ATP to selected tyrosine side chains on specific protein including itself (autophosphorylation).
The first step after binding of ligand is to autophosphorylate.
What type of pass receptor is PDGFR and other growth factor receptors?
single-pass transmembrane
Type of receptor? (Insulin and IGF-I)
Four subunits:
- 2alpha (bound by disulfide bonds) bind extracellular ligand
- 2beta (tyrosine kinase activity)
Definition of a Kinase
Uses ATP to add phosphate groups
Definition of a Phosphatase
Removes phosphate groups
Definition of a Phosphorylase
Adds inorganic phosphate without using ATP
Definition of a Dehydrogenase
Oxidizes substrates by using an electron acceptor (NAD or NADP)
Definition of a Carboxylase
Adds carbon units with help of biotin
Where is the majority of Na+
Extracellulary
Where is the majority of K+
Intracellulary
What is the ratio of Na+/K+ exchanged by the Sodium-Potassium ATPase?
- 3Na+ out
- 2K+ in
What drugs can inhibit the sodium-potassium ATPase?
- Cardiac glycosides (Digoxin, Digitoxin)
- Ouabain (inhibits by binding to K+ site)
What is the end-result of blocking the sodium-potassium ATPase?
Indirect inhibition of Na+/Ca2+ exchange –> Increased intracellular Ca2+–> increased cardiac contractility
What does Clathrin bind to?
Adaptin
What is the function of Dynamin?
It pinches of the developing clathrin-coated vesicle so that it becomes a vesicle
What does Adaptin bind to on the other side of clathrin?
A cargo receptor
In receptor-mediated endocytosis what happens after uncoating of clathrin from endosomal vesicle?
The receptor is recycled back to the plasma membrane and the vesicle fuses with a lysosome
What can be an outcome of an LDL receptor with an abnormal coated pit binding site?
Familial hypercholesterolemia
What is the function of Arachidonic Acid derivatives?
Tissue-tissue communication. They are communicating substances
Name three major derivatives of Arachidonic acid
- Leukotrienes
- Prostacyclines
- Prostaglandins
Arachidonic acid derivative pathway. Step 1?
Membrane phospholipid (specifically Phosphatidylinositol) is converted to Arachidonic Acid by Phospholipase A2.
What can inhibit Phospholipase A2?
Corticosteroids
Arachidonic acid derivative pathway. Step 2A1?
Arachidonic acid is converted to Hydroperoxides by Lipoxygenase
What can inhibit Lipoxygenase?
Zileuton
Zileuton is used as asthma medication because it blocks the production of?
Leukotrienes
Arachidonic acid derivative pathway. Step 2A2?
Hydroperoxides are converted to Leukotrienes (LTB4, LTC4, LTD4)
What is associated with LTB4?
Neutrophil chemotaxis (Increased LTB4 attracts Neutrophils)
What is associated with LTC4 and LTD4?
Increased bronchial tone (which is why blocking of Leukotrienes is helpful in asthma patients)
What drugs block the Leukotriene receptors? (specifically LTC4 and LTD4)
- Zafirlukast
- Montelukast (Approved for pediatric population)
Arachidonic acid derivative pathway. 2B1?
Arachidonic acid is converted to Endoperoxides (PGG2, PGH2) by Cyclooxygenase (COX-1, COX-2)
Only COX-2 inhibitors?
Celecoxib
Irreversible inhibitor of COX
Aspirin
Why does acetaminophen not have antiplatelet and antiinflammatory effects?
Acetaminophen is inactivated peripheraly
Inhibitors of COX
NSAIDS, celecoxib, Aspirin, Acetaminophen
Arachidonic acid derivative pathway. Step 2BA?
Endoperoxides are converted to Prostacyclin (PGI2) (“Platelet Gathering Inhibitor”)
Effects of PGI2?
Decreased:
- Platelet aggregation
- Vascular tone
- Bronchial tone
- Uterine tone
Analogs of Prostacyclins can be used to treat?
Raynaud phenomenon and pulmonary hypertension (due to vasodilatory effects)
Arachidonic acid derivative pathway. Step 2BB?
Endoperoxides are converted to Prostaglandins (PGE2, PGF2a).
Effects of Prostaglandins?
- Increased Uterine tone (Induce labour, Abortifacient (induce uterine contractions))
- Decreased: Vascular tone and Bronchial tone
- Increased gastric mucous production
Arachidonic acid derivative pathway. Step 2BC?
Endoperoxides are converted to Thromboxane
How is Thromboxane associated with thrombose formation?
Thromboxane is prothrombotic
Effects of Thromboxane?
Increased:
- Platelet aggregation
- Vascular tone
- Bronchial tone
Which Arachidonic acid derivative causes Increased bronchial tone?
- Leukotrienes (LTC4, LTD4)
- Thromboxane (TXA2)
Which Arachidonic acid derivative causes decreased bronchial tone?
- Prostacyclin (PGI2)
- Prostaglandins (PGE2, PGF2a)
Which Arachidonic acid derivative causes increased platelet aggregation
Thromboxane (TXA2)
Which Arachidonic acid derivative causes decreased platelet aggregation?
Prostacyclin (PGI2)
Which Arachidonic acid derivative causes increased uterine tone?
Prostaglandins (PGE2, PGF2a)
Which Arachidonic acid derivative causes decreased uterine tone?
Prostacyclin (PGI2)
Which Arachidonic acid derivative causes increased vascular tone?
Thromboxane (TXA2)
Which Arachidonic acid derivative causes decreased vascular tone?
- Prostacyclin (PGI2)
- Prostaglandins (PGE2, PGF2a)
What are the two most abundant substances in plasma membranes?
Proteins and Phospholipids
What drugs act on the arachidonic acid product pathway? What enzymes do they affect?
Corticosteroids: -Inhibit phospholipase A2 Zileuton: -Inhibits lipoxygenase Zafirlukast and Montelukast -Inhibit leukotriene receptors NSAIDs, acetaminophen, COX-2 inhibitors, aspirin -Inhibit cyclooxygenase