P125 Transmembrane Protein

Proteins are important elements in cellular membranes and give the membranes many of their characteristics. In red blood cells, the meshwork of proteins in and around the membrane gives it strength and flexibility, allowing a cell to squeeze through small capillaries without bursting. Other proteins play roles in transporting material in and out of the cell (Lab Manual, Cell Biology). Polyacrylamide gel electrophoresis (PAGE), with all of its different modifications is probably the most widely-utilized procedure in contemporary biochemistry and molecular biology (Mordacq and Ellington (1994)). In this experiment, we will attempt to determine the molecular weights of the major proteins in the plasma membranes of bovine red blood cells (RBCs). The predictions made are if our protein has similar weights as proteins

Cell membranes are surrounded by a phospholipid bilayer that provides a semipermeable barrier for cells, separating the cytosol from the extracellular environment. Phospholipids are ampithatic, meaning that they have a hydrophilic head and hydrophobic tail, which causes the heads to face outwards towards the water and the tails inwards, creating the bilayer [figure 1]. Small hydrophobic molecules such as O2 and CO2 and small uncharged polar molecules such as H2O and ethanol can diffuse through this bilayer, however larger molecules and ions cannot, and thus require proteins, which are polymers of amino acids joined together by strong peptide bonds. These proteins feature throughout the membrane, and account for around 50% of its mass [http://www.ncbi.nlm.nih.gov/books/NBK9898/] . Not only are proteins required for transport of molecules through the membrane, but they also transport signals and are necessary for the cell support; throughout this essay I will focus on the pivotal role they play with regards to the transport of these molecules and signals, and what occurs when these functions are inhibited.

A cell membrane functions as a selective barrier between the cytoplasm and the extracellular fluid. This allows the cell to monitor what is permitted into and out of the cell because some molecules are permeable and others are not. The membrane is composed of phospholipid molecules that are characterized by their amphipathic nature, which means there is a polar and nonpolar end of the molecule. The head is water loving or hydrophilic and the tail is lipid loving or lipophilic. The difference in

The four main parts of the plasma membrane are phospholipid bilayer, membrane proteins, cholesterol, and polysaccharides. The phospholipid bilayer prevents all water soluble substances from crossing the plasma membrane. Membrane proteins are responsible for regulating the entry/exit of vital materials and anchor cells together. Cholesterol regulates the fluidity of the membrane. Polysaccharides acts as receptors and self-identification markers.

Summary of Lipid Dynamics Project. Lipid membranes are highly dynamic. Lipid membranes are highly dynamic. In 1972, Singer and Nicholson introduced the mosaic bilayer model, which suggests that membranes are two dimensional homogeneous liquid. Nowadays with a better understanding of the dynamics occurring at the molecular level of membranes, we are aware of their transverse and lateral heterogeneities. Studies suggest the existence of the so called lipid rafts. These are sub-domains with unique lipid and protein composition, in general with high concentrations of cholesterol and glycosphingolipids. They are believed to play an important role on cell

The cell membrane (also known as the plasma membrane) is a “thin semi-permeable membrane that surrounds the cytoplasm of a cell” (Bailey, 2010). The purpose of cell membrane is to serve as a barrier or gate keeper. Some molecules are able to diffuse across the lipid bilayer while others are prohibited from entering the cell. (The Editors of Encyclopædia Britannica, 2016). Allowing only specific molecules to enter the cell and keeping others out of the cell is what gives the cell membrane the “semipermeable” characteristic (Bailey,

The transport activity is expressed as nmoles of substrate transported during the incubation time per milligram of the reconstituted protein and it is calculated with the following formula:

Unlike integral proteins, peripheral proteins do not extend into the hydrophobic region of the bilayer but remain bound to the surface of the membrane. They are often anchored to an integral protein and are also easier to analyze for scientists since

Protein molecules are made soluble in buffered liquid and isotopically labeled. Therefore, allows thermodynamics, studies of the kinetics aspects of structures and interactions with other components.

Plasma membrane is a border that covers all cells. This coating is difficult, due to the parts always moving allowing specific materials into the cell and keeping substances away. Phospholipid bilayer is what plasma membrane is made of, and they are membrane proteins. “Because it is made of different pieces that form a pattern and seem to float and move in watery environments” (Daempfle, 2016) the plasma membrane is called the fluid mosaic. The fluid mosaic model consists of several macromolecules. Integral proteins spread the whole lipid bilayer; peripheral proteins which sits either inside or outside of the membrane. These two macromolecules serve as foundation cells to one another to transport materials across the membrane, take in chemicals,

On our SDS-PAGE, our protein standards were separated alongside our protein samples which allowed determination of the sizes of our protein in our sample. SDS denature proteins and coats them with a negative charge allowing for their electrophoretic separation by polyacrylamide gel electrophoresis (PAGE). As you can see, after being stained with the coomassie blue, we could detect proteins of various sizes and our unknown protein expressing GST was detected in our Pure B sample (Figure 2). The distance travelled from the wells on the SDS-PAGES by our protein standards were measured and compared to our protein ladder in Daltons (Table 2), from which we could construct our semi log plot. On the semi-log plot, our unknown protein within our Pure B travelled 27mm from the well with a size of 29,000 Dalton (Figure 3). To identify the specific protein in the gel, the western blotting method was used to detect which of the cultures (A or B) contains GST (Figure 4). After the cassette was taken out of the electrophoresis unit, colors of our protein standards appeared on top of our membrane surface. After blocking, primary antibody incubation, and secondary antibody incubation, we could clearly identify our GST in our Pure B and Crude B (Figure

Eukaryotic cells use around 5% of their genes in order to synthesise lipids. There are many different types of lipids present in membranes. Firstly, phospholipids are the most abundant type of lipid in all biological membranes and are composed of a hydrophilic phosphate head and a hydrophobic fatty acid tail. Some membranes also contain glycolipids, which are sugar containing lipids. In eukaryotic membranes, but not prokaryotic membranes, cholesterol can be found, which is a lipid and steroid. Whilst lipids do play a structural role in membranes and function in compartmentalisation, lipids also have many functions in the cell. In this essay I will discuss how lipids play a role in the ability of receptors to function, budding and fusion, fission,

Cells use receptors to recognize a signal, and each signal has a specific receptor (“Cell Signaling”). Receptors bind to signal molecules that act as ligands, molecules that bind to another molecule which cause the receptor to change shapes (“Cell Signaling”; Urry et al. 109). Receptors are usually transmembrane proteins located on the plasma membrane which includes enzyme-linked receptors, ion channel receptors, and G-protein coupled receptors. These receptors use the signals received to affect the function of the cell without harming the cell. Enzyme-linked proteins are typically activated by enzymes (“Cell Signaling”). Ion channel receptors open and close, allowing specific ions to move in and out (“Ion Channel.”) An example of an ion channel receptor is a ligand-gated ion channel which is important for the nervous system. The largest group of transmembrane receptors are G-protein coupled receptors or GPCRs. GPCRs use a G protein that bind GTP. These receptors have many functions including embryonic development and helping with taste and smell (Urry et al. 110). Cells use the receptors on the outside of the cell, but cells also use receptors on the inside.

The experiment is conducted to find out how the membrane is affected by different temperatures. Betalain pigment increases with high temperatures because most mammalian proteins denature and tertiary structure unravels because the strong covalent bonds between the R groups of amino acids in the polypeptide chains are destroyed at

The erythrocyte cell membrane comprises a typical lipid bilayer, similar to what can be found in virtually all human cells. Simply put, this lipid bilayer is composed of cholesterol andphospholipids in equal proportions by weight. The lipid composition is important as it defines many physical properties such as membrane permeability and fluidity. Additionally, the activity of many membrane proteins is regulated by interactions with lipids in the bilayer.