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.
antimicrobial proteins
— proteins that specifically damage or kill bacteria.
• ex: antimicrobial proteins such as proteases, which kill various bacteria by destroying essential proteins; and lysozyme, which attacks the cell walls of gram positive bacteria
defensins
Some antimicrobial peptides, like defensins, attack bacterial cell membranes.
binding proteins
competitively bind to proteins or ions that would have otherwise been beneficial to bacteria or viral replication. They’re important players in the immune system
How do we get calculate VM (membrane potential)?
- VM = 61.5 x log ( [K+out] / [K+in] )
- Examples of membrane potentials for different ions (for a cell that’s was only permeable to one ion):
- K+ = -67mV (positive ions moving outside cell) • Na+ = +67mV (positive ions moving into cell)
- Cl– = -87mV (negative ions moving into cell) • Ca2+ = 123mV (positive ions moving into cell)
- note that because Ca2+ has a 2+ charge, the 61.5 gets changed to 30.75 in our VM equation.
• When the electrons move from protein to protein, , is it going from low to high energy or opp?
• When the electrons move from protein to protein, they’re going from a higher energy state to a lower energy state, releasing energy in the process. This energy is used to pump H+ ions out of the matrix into the intermembrane space.
cyt c is for complex 3
chemiosmosis
• The intermembrane thus becomes acidic while the matrix becomes basic, creating a concentration and electropotential gradient. The H+ ions will want to go back down their gradient, but remember the inner membrane is impermeable
= H+ ions passing through channel in ATP synthase to make ATP
crinophagy
is when lysosomes digest excess secretory product.
• ex: if cells produce extra of a hormone that needs to be secreted, lysosomes will break down that extra via crinophagy.
acid hydrolase
- Enzymes in the lysosomes are known as acid hydrolases; they require an acidic environment to work properly. The pH in a lysosome is ~5, which acts as a safety mechanism for the cell.
- If for some reason a lysosome were to burst, it would release into the cell’s cytoplasm all the acid hydrolases that break down organelles and other molecules… but those hydrolases wouldn’t be able to work because the pH of cytoplasm is ~7.4!
simple epithelial tissue
is found where substances needs to diffuse from two different sites
• ex: Alveoli of lungs are lined with simple epithelium so O2 and CO2 can diffuse from alveoli
stratified epithelial tissue
can be found in places that need to resist chemical/mechanical stress
• ex: The esophagus intakes food that may be sharp, hot, large, etc.. stratified cells protect it.
how do epithelial cells get nutrients since they are avascular
- Epithelial cells are attached to a basement membrane that is made of different kinds of fibers (e.g. collagen) rather than cells.
- The basement membrane is semi-permeable to certain substances, which is important because epithelial cells are avascular; they have no blood vessels.
- Instead, epithelial cells get nutrients from underlying tissue. Nutrients diffuse from tissue through basement membrane into epithelial cells.• Epithelial cells are attached to a basement membrane that is made of different kinds of fibers (e.g. collagen) rather than cells.
- The basement membrane is semi-permeable to certain substances, which is important because epithelial cells are avascular; they have no blood vessels.
- Instead, epithelial cells get nutrients from underlying tissue. Nutrients diffuse from tissue through basement membrane into epithelial cells.
does adipose tiss have fibers?
it is the only conn tiss that does not have fibers
blood doesn’t have fibers either
areolar tissue is
type of conn tiss that binds to different types of tissue and provides flexibility and cushioning.
fibrous conn tiss
very strong. provides support and shock absorption for bones and organs.
• Fibrous connective tissues is found in dermis (middle layer of the skin), tendons, and ligaments
what makes microfilaments diff from flagella or cillia
Note that this gross movement comes from within the cell (as opposed to cilia & flagella, which help move the cell from the outside).
• Microfilaments are found in the cytoplasm.
• They’re composed of a protein called actin. Many molecules of actin join together to form an actin polymer; many actin polymers twist around each other to form actin filaments.
- ex: Microfilaments help the cell divide; they help make the pinched shape & help actual division occur.
- ex: Microfilament are responsible for the ameboid movement of macrophages (e.g. white blood cell engulfing a pathogen).. An amoeba has projections known as pseudopods, which reach out to grab food and ingest it. Pseudopod movement is aided by microfilaments.
how r intermediate fillaments differ from microtubules and microfillaments
- In contrast to microtubules and microfilaments, these are made of many different kind of proteins that are strung together into polymers, which then twist together to make intermediate filaments.
- Also unlike microtubules and microfilaments, intermediate filaments are pretty permanent. Once they’re made in the cell they stay put (Microtubules & microfilaments are dynamic)
kinetichore
A protein kinetichore structure surrounds
the centromere and serves as an anchoring site for the
kinetichore fibers which come out of the kinetichore.
• Those kinetichore fibers are what turn into microtubules.
prok flagellin vs euk flagellin
proks is made of the protein flagellin rather than
microtubules). These help bacteria move toward nutrients via chemotaxis (sensing chemicals and moving towards / away from it)
what are inclusion bodies
Bacteria also have inclusion bodies that store stuff (e.g. nutrients) for the bacteria. This is important in prokaryotes because they have no membrane-bound organelles
diff of plasma membrane btwn gram pos and neg bacteria
neg has two plasma membranes and has liposacharides and an inner lipid layer… repsonds more to protection against antibiotics
how many origin of replication are there
it can have just one origin of replication.
• At this origin, the initiator protein comes in, then 2 DNA polymerases enter to start replication in opposite directions… They eventually just run into each other on the circle.
endospore
Recall, gram-positive bacteria have a super thick cell wall. When they start to sense the toxicity in the environment, some can change their wall chemistry to be super reinforced and seal itself off.. this endospore is then resistant to heat, radiation, toxic chemicals, etc… it can even survive in boiling water for an hour! The endospore “rescues” the bacteria until it gets in an environment that has nutrients again and can be activated
conjugation
horizontal transfer
A bacteria that has a fertility factor in the plasmid and is fertility positive (F+) will create a sex pilus — basically a protein tube — that connects the f+ bacterium to an f- bacterium.
nucleocapsid
= protein coat + nucleic acid
direct fusion
If a virus has that membrane envelope that give the virus a spherical shape, it has an extra option to get in. Enveloped viruses can still enter via receptor-mediated endocytosis, or they can get in by direct fusion, which is when the envelope around the virus fuses with the membrane and gets virus in that way.
retrovirus
use direct fusion
are enveloped ssRNA virus. Three special proteins (reverse transcriptase, integrase, protease) are also carried in the envelope.
