James Rothman, Randy Schekman and Thomas Südhof's Research on Transport Vesicles

Membranes can allow or exclude various molecules, and because of selective transport systems (active mediated transport), they can move molecules in and out of the space. Membrane channels, or “gates,” can open and close depending on the circumstances of the first messenger. Binding of an extracellular messenger to a dual receptor/channel brings about a quick

Phospholipids make up most of the cell membrane, in a phospholipid bilayer. Phospholipid molecules form two layers, with the hydrophilic (water loving) head facing the extracellular fluid and the cytosol (intracellular) fluid, and the hydrophobic (not water loving) tails facing one another. The cell membrane is constructed in such a way that it is semipermeable, and allows oxygen, CO2 and lipid soluble molecules through easily, while other molecules like glucose, amino acids, water, and ions cannot pass through quite as easily. That is the meaning behind the chant “some things can pass, others cannot!”.

List three criteria cells use to select materials to enter or leave the cell. Then explain the role of each criterion in determining the type of transport a cell will use for different sized molecules. For instance, small molecules move across the membrane by diffusion, given they are moving with the concentration gradient.

[1] – Molecular Cell Biology, 7th edition 2012, Harvey Lodish, Chris A. Kaiser, Anthony Bretscher, et al. Macmillian Higher Education.

Second, in order to further confirm the information about characteristics and function of the targeting protein that we have

Explain the effect that increasing the Na+ Cl- concentration has on osmotic pressure and why it has this effect. How well did the results compare with your prediction?

What happens to the urea concentration in the left beaker (the patient)? It mixes with the water to balance out the structure.

The purpose of these experiments is to examine the driving force behind the movement of substances across a selective or semiperpeable plasma membrane. Experiment simulations examine substances that move passively through a semipermeable membrane, and those that require active transport. Those that move passively through the membrane will do so in these simulations by facilitated diffusion and filtration. The plasma membrane’s structure is composed in such a way that it can discriminate as to which substances can pass into the cell. This enables nutrients to enter the cell, while keeping unwanted substances out. Active

Molecules move around the cells through vessels. There are three different ways that molecules enter the cell diffusion, facilitated diffusion and active transport. Diffusion is when a molecule moves from high concertation to low concentration. Facilitated diffusion is when the molecules goes through a plasma membrane. Active transport is when an organism uses energy to move molecules. The three scientist discovered the different aspects to make sure and understand the research of making sure that the right cargo is shipped to the correct destination at exactly the right time. The scientist use the example of a pancreas. The pancreatic cells make insulin and release it in the blood. Chemical signals called neurotransmitters are sent from one nerve cell to another, this allow humans to have some of the functions they have today. The discoverers discovered that the molecules move at a fast pace within the cell and also they used the comparison of rush hour traffic to the molecules moving within the cells. Dr. Schekman discovered a set of genes that were required for vesicle traffic. To discover better research on this experiment he compared two cells, one that was normal and one that was mutated. Dr. Rothman discovered protein machinery that allows vesicles to join with their targets to go through with the transfer of cargo. Proteins on the vesicle bind to specific distinguished proteins on the target membrane, to make sure that the vesicle joins at the specific location and that cargo molecules are delivered to the correct destination. Dr. Südhof revealed how signals give orders to vesicles to release their cargo with precision. He studied how signals are directed to one nerve cell to another. He also discovered how calcium controls this process and that it controls certain things at the

The identified candidate protein is Synaptotagmin-1. Synaptotagmin-1 is a protein which positively affects the release of neurotransmitters by acting as a calcium sensor (Lau et al, 2013), so it is expected for the protein to be located in the pre-synaptic terminal of an axon. It has four distinct domains, two of which are very similar. The first domain is the N-terminal transmembrane domain (CDD). This domain was found to be located on the plasma membrane (Feany et al, 1993). Because the role of the protein as a whole is to enable vesicular fusion, it seems logical to assume that the protein must be anchored on the plasma membrane, and it would be a logical assumption to make that the role of this domain is to anchor the protein down.

As soon as the electrical signal reaches the end of the axon, mechanism of chemical alteration initiates. First, calcium ion spurt into the axon terminal, leading to the release of neurotransmitters “molecules released neurons which carries information to the adjacent cell”. Next, inside the axon terminal, neurotransmitter molecules are stored inside a membrane sac called vesicle. Finally, the neurotransmitter molecule is then discharged in synapse space to be delivered to post synaptic neuron.

The movement of molecules have two forms of transport through the plasma membrane: active transport and passive transport. Active processes require energy, such as ATP, in order for the molecules to be transported. In active transport, the cell administers ATP.i Within passive processes no energy is required and changes n pressure and concentration are the driving forces. Processes such as simple diffusion, facilitated diffusion, osmosis, and filtration are characterized as passive transport, while solute pumps are a form of active transport. Each of these form of transports occur in the cells of all living organisms and are essential to life.

If the solution in the left beaker contained both urea and albumin, which membrane(s) could you choose to selectively remove the urea from the solution in the left beaker? How would you carry out this experiment?

The Transport of Substances Across the Plasma Membrane The plasma membrane or, the cell surface membrane, is made almost entirely of protein and lipid. The plasma membrane controls the movement of substances into and out of a cell. It is partially permeable so some substances cross more easily than others.

Overexpression of the HEPN domain in HeLa cells following three hours of starvation indicates that sacsin plays a key role in lysosomal transport due to the reduced efficiency of perinuclear lysosomal clustering. HEPN’s property of dimerizing may be disrupting the function of with full-length sacsin by preventing endogenous sacsin from dimerizing within the cell. Thus, dimerization may be essential to sacsin’s function, particularly for binding JIP3, which is necessary for lysosomal transport7. HATPase 3 overexpression may be occupying JIP3 binding, but was not found to disrupt lysosomal localization following starvation, perhaps due to the truncated size of this deletion construct.