membrane Flashcards
1
Q
phsophotidylinositols are involved in _____
phsophatidylserine is normally maintain ___
A
- signaling
- inside
2
Q
5 factors affecting flexibility of acyl groups in the bilayer
A
- temperature (20-40degree)
- saturation of FA increases order
- uniform lenght of FA chains increases order
- sterol content affects both ways
- cells regulate FA content of the membrane (increase saturated FA at higher temperature)
3
Q
3 characteristics of lipid rafts
A
- contains clusters of glycosphingolipids
- are more ordered
- contain specific doubly or triply acylated proteins
** Contain sphingolipids that can form more compact, more stable associations with the long ring system of cholesterol that can can the shorter, often unsaturated, chains of phsopholipids
4
Q
6 things fusion membrane requires
A
- triggering signal
- recognize each other
- close apposition (In order to fuse, they have to be close physically, which requires the removal of water molecules normally associated with the polar head groups of lipids)
- local disruption of bilayer
- hemi-fusion (Fusion of the outer leaflet of each membrane)
- fusion proteins
5
Q
8 examples of membrane fusion
A
- budding of vesicles from golgi complex
- endocytosis
- exocytosis
- fusion of endosome and lysosome
- viral infection
- fusion of sperm and eggs
- fusion of small vacuoles (plants)
- separation of two plasma membranes at cell division
6
Q
4 proteins involve in the membrane fusion at synapse
A
- 3 types of SNARE ae involved:
1. T-SNARE assemble on the target membrane (with which the vesicles fuses)
2. V-SNARE assemble on the vesicle membrane
3. Q-SNARE (SNAP-25) are regulatory proteins that are Ca2+ induced. ** it helps V-snare and T-snare to come together
- 3 types of SNARE ae involved:
- NSF (N-ethylmaleimide-sensitive fusion factors) proteins disassemble the SNARE complex
7
Q
6 steps of membrane fusion at synapse
A
- neurotransmetteurs-filled vesicle approaches plasma membrane
- v-SNARE and t-SNARE bind to each other, zipping up from the amino terminal and drawing the 2 membranes together
- zipping causes curvature and lateral tensionon bilayers, favorising hemifusion between outer leaflets
- hemifusion: outer leaflets of both membranes come into contact
- complete fusion creates a fusion pore
- pore widens: vesicle contents are released outside the cell
8
Q
6 types of solute transport accross membrane
A
- simple diffusion
- facilitated diffusion (with a protein transporter): down an electrochemical gradient
- primary active transport: against electrochemical gradient, driven by ATP
- secondary active transport (against electrochemical gradient, driven by ion moving down its gradient)
- ion channel (down electrochemical gradient, may be gated by a ligand or ion)
- ionophore-mediated ion transport (down electrochemical gradient)
9
Q
GLUT1,2 and 4: where are they + their role
A
- belonged to the class acyl transporter since they don’t required energy, so its down the gradient, passive transport
1. GLUT1: expressed in erythrocytes and most tissues at a lower level, role: basal glucose uptake
2. GLUT2: expressed in liver, pancreatic islets, intestine, kidney, role: in liver and kidney
3. GLUT4: muscle, fat, heart, role: activity increase by insulin
- belonged to the class acyl transporter since they don’t required energy, so its down the gradient, passive transport
10
Q
5 steps whith insulin dependent glucose transporter
A
- glucose transporters are stored within the cell in membrane vesicles
- when insulin interacts with its receptors (PIP3 will be activate), vesicles move to the surface and fuse with the plasma membrane, increasing the number of glucose transporters in the plasma membrane (so increasing the uptake of glucose inthe cell..)
- when insulin levels drop, glucose transporters are remove from the plasma membrane by endocytosis, forming small vesicles.
- the smaller vesicles fuse with a larger endosome
- patches of the endosome enriched with glucose transportes bud off to become small vesicles, ready to return to the surface when insulin levels rise
** lack of transcription = diabetes mellitus!!
11
Q
what is the way of CO2 in respiring tissue and lungs (what is the enzyme tha converts it to bicarbonate..)
A
in respiring tissue:
- CO2 produces by catabolism enters erythrocytes.
- CO2 will be convert into bicarbonate (HCO3-) by carbonic anhydrase.
- chloride-bicarbonate exchange protein brings the Cl- inside and the HCO3- outside the cell
in lungs:
- HCO3- enter erythrocytes from blood plasma and Cl- goes out
- carbonic anhydrase converts it to CO2
- CO2 leaved the erythrocytes and is exhaled
** all of this is facilitated passive transport!!!
12
Q
2 examples of secondary active transport
A
- symport: Na+ : glucose and Na+: amino acid in the epithelium intestine
(so Na+ goes out first driven by ATP and this will allow the glucose and the Na+ to go in after without ATP_ - antiport: Na+: K+-ATPase; Na+: H+ pumps in kidney
13
Q
7 solutes tranported by ABC transporters in the cell
A
amino acids peptides proteins drugs bile silts lipids metal ions
14
Q
different cells require different metabolic pathways, give 3 examples
A
- tissue repair requires energy and biosynthetic precursors
- neurons depend more on glucose (like RBC)
- cardiac myocytes depend more on FA
15
Q
10 steps of regulation of enzymes
A
- extracellular signal
- transcriptional regulation (TF phosphorylation/dephosphorylation, TF interactions)
- mRNA stability
- mRNA translation
- proteins stability (half-life) ex: cyclins
- enzyme localization (ex: mitochondrial enzymes)
* * methods 1-6 regulate levels of enzymes, which can e measured - changes of level of substrate
- enzyme binding allosteric effectors
- covalent modification
- interaction with regulatory proteins
