Lipid membrane and solute transport Flashcards
Why the membrane is called mosaic?
Because it consists of different kinds of molecules
The integral proteins are called like that because
They are embedded in the membrane. They can pass through the lipid bilayer or only on one side
Example of integral proteins
Receptors ( GPCRs)
Why do detergents are needed to detach the integral proteins form the membrane?
Because they are strongly associated with it
What does amphitropic protein mean
Having an affinity for both lipid and aqueous environments. Thus, if needed they can detach from the membrane and play its role in the aqueous environment
What do you need to make amphitropic proteins detach from the membrane?
Some kind of enzyme ( phospholipase C) or postranslational modification (phosphorylation)
What is GPI?
Glycosylphosphatidyllinositol
An example of GPI linked protein
Phosphatases
Different organelles within the cell have different ____
Cell wall components ( the ratio of components)
Inner and outer cell membrane ___ each other
Differ from each other
What molecules are involved in cell signaling in the cell membrane
phosphatidyllinositol
Most of phosphatidyllinositol is inside/outside of the cell
inside
Phosphatidylserine is usually maintained
Inside of the cell
When Phosphatidylserine flips to the outer membrane, then
It signals for apoptosis or blood clot
Acyl groups in the bilayer affect
Flexibility
There are two states of the bilayer
Ordered state(Lo) and disordered state(Ld). It is a range of temperatures rather than points
The transition from Lo->Ld of side chains is a result of
Heat that produces thermal motion in side chains. The more temperature it is exposed to, the more disordered the side chains will be.
What increases order in the bilayer
Saturation of FA
Uniform length of FA
Sterol content can decrease or increase order
How do cells regulate the membrane
FA content ( increase Saturated FA at higher temperatures)
Ordered state is more ___, and disordered is more ___
Rigid
Flexible
uncatalyzed lipid movement ( what direction)
Lateral diffusion
three catalyzed transbilayer translocation
flippase (from outer to inside)
Floppase ( form inside to outside)
Scramblase ( moves lipids in either direction, toward equilibrium)
what enzymes perform flippase and floppase
Flippase- P-type ATPase
Floppase- ABC transporter
With the use of ATP
What holds protein in the bilayer
Cytoskeleton
Lipid rafts
Sphingolipids give __ to the bilayer
Order, thus more rigid.
Sphingolipids give order to an area, not flexible within the region, but as a whole free to move
Lipid rafts contain specific___
Double or triply acylated proteins
6 things for two membranes to fuse
- triggering signal
- recognize each other
- close apposition
- local disruption of bilayer
- hemifusion
- fusion proteins
All neurotransmitters are stored in ___
Vesicles
Four types of proteins that are involves in fusion at synapse
T-SNARE
V-SNARE
Q-SNARE(SNAP-25)
NSF (N-ethylmaleimide-sensitive fusion factor)
What does T-SNARE do
They are assembled on the target membrane. At this pont of time the cell should know at what part of the exon( because it is huge) it will secret the neurotransmitters. This is done by them
What does V-SNARE do
It recognizes the vesicle that should be emptied out. It is assembled on the vesicle site
What do Q-SNARE do
They help T-SNARE and V-SNARE to come together
They are induced by Ca
The stages in fusion of the vesicle with neurotransmitter
1) The vesicle has V-SNARE and the plasma membrane has T-SNARE. SNAP-25 helps this two to come together
2) V and T bind to each other and start to zip, thus they are brought closer to each other
3) When the vesicles are brought close enough to each other, hemifusion occurs between outer leaflets
4) Hemifusion-> full fusion. Now the vesicle can open up, because it is part of the membrane
What does NSF do
They disassemble the proteins that were bound to each other, the SNARE complex
Three glucose transporters that are studied a lot
Glut 1
Glut 2
Glut 4
Glut 1,2 and 4 belong to what kind of transporters
Passive, do not need energy, down the concentration gradient
Glut 4 is regulated by what mechanism
RTK and PIP3 and PKB
How GLUT 4 is regulated
Amount of transporter presented in the cell membrane by RTK
thus regulating how much glucose is available for glucose transport. The more transporters are available, the more glucose goes from outside to inside. If no RTK signal, transporters are stored in the cell in vesicles
What is diabetes mellitus ( biochemically)
Lack of signal transduction of RTK, thus less transporters come form the inside to the outside-> less glucose uptake
Respiration is what kind of transport
Facilitated passive transport
Explain what happen in erythrocyte when it comes to respiring tissue
CO2 diffuses through the membrane inside the erythrocyte. CO2+H2O->HCO3-+H+
HCO3- is thrown outside the membrane and CL- is taken in by a cotransporter(antiporter)
What is the enzyme for conversion of CO2 to HCO3-
carbonic anhydrase
What happens in lungs
The same reaction as in erythrocyte but in reverse.
Cl- is given off, HCO3- is taken, converted to CO2 and given to lungs
Two types of active transporters
Primary active transport
Secondary active transport
Explain the difference between primary active transport and secondary active transport
Primary- with the use of ATP, the molecule is transported across the concentration gradient
Secondary- an artificial gradient of one molecule is created by pumping it across the gradient, to allow another protein to use this gradient to transport another molecule symporter)
An active transport: symport example and antiport example
Symport: Na+ glucose, Na+ AA in intestinal epithelium
Antiport:Na+K+ATPase,Na+H= pumps in kidney
What type of ATPases in used in mitochondria
F type
Explain ABC transporters
When ATP is boiund to the cassette, the transporter is opened outward, when ADP- inward, when the molecule comes there is a change in conformation, because of ATP\ADP
RBCs comparing to the stem cell does not have
Nucleus and mitochondria
As RBCs do not have mitochondria what does it mean for them
They cannot produce energy and they rely only on glycolysis
Tissue repair requires____
Energy and biosynthesis precursors
Neurons depend more on ___
Glucose
Cardiac myocytes (muscles int he heart) depend more on ___
FAs
Where can the regulation be inserted in the cell
- Extracellular signals
- Transcription regulation (a-TF phosphorylation/dephosphorylation,b-TF interactions)
- mRNA stability (degradation)
- miRNA) - mRNA translation
- Protein half-life (stability)
- Enzyme localization
- Changes of levels of substrate( the more substrate- the more active the enzyme)
- Enzyme binding “allosteric effectors”
- Covalent modification
- Interaction with regulatory protein
The longer mRNA is maintained within the cell- the longer it is going to be ___
Translated, the more protein produced
What are cyclins
Proteins involved in cell cycle- cell division, their half-life is very short
Mitochondrial enzymes are only functional
In mitochondria
Pathways in opposite directions are not favored ___. For example
At the same time
Glycolysis and Gluconeogenesis
