Cell And General Physiology Flashcards
What are the intracellular and extracellular concentrations of:
Na+ K+ Ca2+ Mg2+ Cl- PO4 HCO3-
Extra Intra Na 145 10 K 4 140 Ca 2.0-2.5 < 1 Cl 105 10 PO4 2 75 Mg 2 50 HCO3 24 10
Nonpolar:
Nonpolar molecules have + and - charges uniformly distributed throughout the molecule; there is no net overall charge.
Oxygen and Sevoflurane are examples
These molecules are lipophilic and hydrophobic
Polar Molecules:
Have no net charge. However they do have regions of + and - clusters
H2O (small) and glucose (large) are examples
These molecules are hydrophilic and lipophobic
Composition of the Cell Mambrane:
Cell membrane is comprised of a phospholipid bi-layer
Lipids:
- Phospholipids (most abundant by #)
- Glycolipids
- Cholesterol
Proteins: (most abundant by weight)
- Channels
- Receptors
- Enzymes
Functions of the Lipid Bilayer:
- Serves as a semi permeable barrier blocking substances that are not small and are not lipophilic
- Provides environment in which membrane proteins can function
Transport Through the Lipid Bilayer:
Hydrophobic lipophilic nonpolar molecules (O2, IV and gas anesthetics) as well as SMALL non charged polar molecules (H2O, CO2) readily pass through the lipid bilayer.
Large uncharged polar molecules (glucose) and ions (Na, K, Cl, etc..) cannot cross and need active transport
Describe the 2 types of endocytosis and give and example of each
Pinocytosis (cell drinking):
Reabsorption of proteins from the proximal tubule of the kidney
Phagocytosis (cell eating):
Macrophages phagocytize bacteria
Describe exocytosis and give an example:
Intracellular vesicle merges with the cell membrane releasing its contents extracellularly.
Neurotransmitters are released from the nerve terminals by the process of exocytosis
Describe Ligand Gated Channels, give an example
These are receptors that control ion channels. When a ligand (drug, neurotransmitter, hormone) attaches to the receptor, the channel opens allowing substances to move down their concentration gradient
Example: Acetylcholine binds to the nicotinic receptor in the neuromuscular junction opening the sodium channel ==> Na and Ca defuse in and K defuses out
Ligand is known as the first messenger
Describe Enzyme-linked Receptors and give an example:
These are receptors that control membrane- bound enzymes. When a ligand attaches to the receptor, an enzyme inside the cell (ie. adenylate cyclase) gets activated and a reaction inside the cell is accelerated by the enzyme.
A second messenger is produced
Describe first and second messengers:
First messengers are ligands (drugs, neurotransmitters etc..) that attach to the receptors
Second messengers are the chemicals generated inside the cell by the enzyme once the receptor has been activated by the first messenger
Describe signal transduction
Signal transduction is the relaying of messages from the exterior to the interior of the cell.
Describe G protein signal transduction
G protein signal transduction can be stimulatory (Gs) or inhibitory (Gi)
The G protein is made up of 3 subunits: gamma, beta, and alpha
When an external ligand (first messenger) attaches to its receptor, a membrane G protein shuttles information to an enzyme (adenylate cyclase) which either accelerates the transformation of ATP ==> cAMP (second messenger) triggering an intracellular event, or inhibits the reaction
List 5 second messengers
(cAMP) cyclic adenosine monophosphate (cGMP) cyclic guanosine monophosphate (IP3-) inositol triphosphate Calcium Calmodulin
Describe the Sodium Potassium ATPase pump and clinical applications
The sodium-potassium ATPase pump shuttles Na and K agains their concentration gradient. This is via active transport and breakdown of ATP.
For every 3 Na+ extruded 2 k+ are imported
Clinical applications:
- Insulin stimulates the Na-K pump and therefore is given in the presence of hyperkalemia along with glucose
- beta-2 adrenergic receptor agonists also stimulate the Na-K pump and can be given to treat hyperkalemia. (i.e. Albuterol)
