KA CELLS Flashcards
clatharate
Lipids cause water to arrange in an ordered, unfavorable cage-like structure which will decre entropy
entropy incr when a phospholipid bilayer is formed
cis double bonds on phospholipids have?
kinks that cam effect the membrane
a transmembrane membrane aka
integral protein (cross the whole phospho bilayer
where is a lipid bound protein found
found within the interior of the bilayer
fluidity vs integrity
• cholesterol: maintains fluidity (at low temps, especially) and integrity (at high temps) of membrane
flippase vs floppase vs scramblase
- Flippase protein — catalyzes the movement of a phospholipid from outer leaflet to the inner, using ATP. Fast compared to transbilayer diffusion
- Floppase protein — catalyzes the movement of a phospholipid from inner leaflet to outer leaflet, using ATP
- Scramblase — catalyzes the simultaneous movement of one phospholipid from inner —> outer leaflet, and a second phospholipid from outer —> inner leaflet. Does not require ATP.
desmosomes (macula adherens)
• Like tight junctions, desmosomes physically hold the cells together, but
do not allow fluids or materials to pass from the inside of one cell to the next.
• These connections are also attached to the cytoskeleton (aka the scaffolding
of the cell) to help with structural support.
• The space in between the cells allows for water and solutes to flow freely between each cell without compromising the connection.
• This is convenient for areas of our body that experience high stress like in our skin or our intestines because the space in between the cells offer flexibility that the other junctions can’t.
ligand receptor complex
Signaling molecules (aka ligands) such as neurotransmitters, hormones, etc. bind to the membrane receptor (with specificity)
3 type of membrane receptors
- Ligand gated ion channels
- G-protein coupled receptors
- Enzyme linked receptors
ligand gated ion channel aka ion gate channel
, these are transmembrane ion channels that open or close in response to the binding of a ligand.
• Commonly found in excitable cells like neurons, because these channels react quickly to binding of a ligand, and thus the cells can respond quickly to stimulus.
• Only specific ligands can bind to specific channels (lock and key / induced fit)
• Note, binding site is no where near actual channel.. ligand binds to allosteric site and alters opening / closing by conformational change.
ligand gated vs voltage gated vs stretch activated
- Ligand gated ion channels are not the same as voltage gated ion channels.. those only depend on a different in membrane potential, not the binding of a ligand
- Ligand gated ion channels are also different from stretch activated ion channels.. which open / close in response to deformation or stretching of the cell membrane
how does a gcpr receptor work
When the ligand binds to the GCPR, it undergoes a conformational change.
(2) Because of the conformational change, the Gα exchanges its GDP for a GTP, becoming activated.
(3) The GTP causes the Gα subunit to dissociate and move away from Gßγ dimer.
(4) Gα subunit then goes on to regulate target proteins
• The Gα subunit dissociates and binds to
adenylate cyclase, which then makes the secondary messenger cAMP from AMP.
• cAMP goes on to increase heart rate, dilate blood vessels, and break down glycogen —> glucose
enzyme linked receptor
• also called catalytic receptors
• transmembrane with a General structure has extracellular “ligand binding domain” and intracellular “enzymatic domain”
most common ex is RTK
RTK
are tyrosine kinases (also called RTKs), which regulate cell growth differentiation and survival; and they can bind and respond to ligands such as growth factors.
• Unique because Tyrosine is on the enzymatic intracellular receptor. RTKs have ability to transfer phosphate groups to intracellular proteins, which activates them, and they go on to trigger additional change.
• RTKs occur in pairs. When ligands bind, the RTKs come together and act together in a cross-linked dimer. This helps activate the Tyr.
protron potassium ATP pump is used for and where is it located?
(H+/K+ ATPase) found in the stomach. These proton pumps are responsible for creating the acidic environment of the stomach, and can cause acid reflux
secondary active transport
transport moves multiple molecules across the membrane, powering the uphill movement of one molecule(s) with the downhill movement of the other(s).
• Uses a gradient (which is set up using energy) instead of ATP for energy
ex: glut2 symporter and calcium/sodium antiporter
ssri effect on depression and second active transporter
SSRI antidepressants are a type of antidepressant that work by increasing levels of serotonin within the brain. Serotonin is a neurotransmitter that is often referred to as the “feel good hormone”. SSRIs work by blocking (“inhibiting”) reuptake, meaning more serotonin is available to pass further messages between nearby nerve cells.
block a specific sodium-neurotransmitter symporter
CXCR4
type of phagocytosis
our body has helper T-cells (which target and kill bad things in the body) that have a receptor on them call CXCR4. This receptor is targeted by the HIV virus protein GP41, which binds to CXCR4. Some people have a genetic alteration in the CXCR4 that does not allow GP41 to bind; these individuals are immune to HIV!
what is endocytosis and what are the diff types
phagocytosis (specific)
pinocytosis (non specific )
receptor mediated endocytosis (very specific)
phagocytosis is :
- Phagocytosis — cell engulfs a molecule in order to move it to the interior of the cell.
- A molecule binds to specific receptors on the surface of the cell membrane, triggering the cell membrane to reshape
opsonin receptors
bind bacteria or other particles that have been coated with immunoglobulin G (or “IgG”) antibodies by the immune system.
• Immune system coats potential threats in antibodies so other cells know it should be destroyed.
• Immune system can use something called the “complement system”, a group of proteins used to tag the bacteria… basically another way for the immune system to destroy pathogens and threats.
scavenger receptors
bind to extracellular matrix produced by bacteria itself.
• Most bacteria and other cellular species produce a matrix of proteins surrounding themselves… It’s a perfect way for immune system to identify foreign species, because human cells do not produce the same protein matrix.
toll like receptors
bind to specific molecules produced by bacteria
• Once they’re bound to a bacterial pathogen, the innate immune system recognizes these toll receptors and activates the immune response.
phagolysosome
- Without fusing with a lysosome, the phagosome wouldn’t be able to do anything with its contents.
- A lysosome or phagolysosome is able to break down its contents by drastically lowering the pH of its internal environment.
