Briefly describe the structure of eukaryotic plasma Membrane, identifying at lea

Question

Briefly describe the structure of eukaryotic plasma Membrane, identifying at least two components macromolecules and describing what is their basic functions in the cells.
Summarize the manner in which small molecules are permitted to pass through the membrane ensuring you explain the difference between passive, facilitated, active, and coupled transport by contrasting and comparing them.

finally explain the difference between endocytosis and exocytosis and provide an example of a molecule ( remembering to State it's function that is transferred using this method.

Explanation / Answer

Ques-1: Briefly describe the structure of eukaryotic plasma Membrane, identifying at least two components macromolecules and describing what is their basic functions in the cells.

Answer:

Three kinds of macromolecule components are present in cell plasma membranes are as follows:

Lipids, proteins, and carbohydrates

Two general meanings of the term "membrane" in biology are to describe the structure of cell membrane that is permeable to some molecules but not all molecules. Second meaning of a "membrane in biological cell" is to protect inner cytoskeleton with organelles. Plasma membrane is made of phospholipid bilayer in which one is hydrophilic region and another is hydrophobic region. The phsopholipid layers indicates layers of lipids and membrane proteins whereas the layers of cells is mainly due to "membrane associated cell adhesion molecules". The inner leaflet is composed of lipid composition made of phosphorylated -phosphatidylserine and phosphatidylinositol compared to the outer leaflet in which glycolysated -phosphatidylcholine, sphingomyelin are major components that contribute asymmetric nature of lipid bilayer in the membrane.

These lipid distribution is evenly maintained within smooth endoplasmic reticulum by flippases so that symmetry will be maintained through both inner and outer leaflet

These three macromolecules together to form a complex phospholipid bilayer in which periplasmic proteins are distributed in a mosaic manner. The large fluid mosaic structure is formed from these macromolecules composed of phospholipid bilayers with protein channels for the transport of organic & inorganic nutrients including trace metal. Normally, the essential aspects of these structures composed of "porins, protein channels, integral proteins” that dictate their function for the "selective permeability (lipids permit movement of lipophillic molecules into the cell)", "diffusion of nutrients" across the membrane into & out of the cell finally to attain homeostasis.

The cells of an organism that normally lives at 15-37 degrees Celsius maintain the structure of its proteins at the elevated temperature of 40 degrees Celsius via various mechanism because proteins possess both defolding (renaturation) & denaturation mechanism along with transition temperature to adapt to the differential environments to main membrane fluidity. Protein denaturation is referred as the process of “change in conformational status of protein” finally results in instability of protein due to lose of the quaternary & tertiary structure at the elevated temperatures. However, if the protein is in secondary structure configuration at the elevated temperature of 40 degrees Celsius is leading to presence of protein in native state so that the cells of an organism that normally lives. The renaturation of the protein defined as the reversible regaining of original protein native structure when removing the temperature altering conditions. For example, the large fluid mosaic structure is formed from these macromolecules composed of phospholipid bilayers with protein channels for the transport of organic & inorganic nutrients including trace metal. Normally, the essential aspects of these structures composed of "porins, protein channels, integral proteins” that dictate their function for the selective permeability, diffusion of nutrients across the membrane into & out of the cell finally to attain homeostasis

Glycerophospholipids (normal eukaryotic cell membranes), sphingolipids (neuronal cell walls, fungal cell walls), and glycolipids are complex macromolecule so that can form hydrophobic micellar structure around the plasma membrane in a variety of species to form a complex cell wall so that they can survive towards harsh conditions. The energy storage containing lipids are the structures of triacyglycerols undergoes beta-oxidation to generate energy at the time of starvation or fasting

Fluid mosaic model describes that two-dimensional liquid layer of cell membrane where proteins distributed like mosaic model in the phospholipid bilayer. This model mostly accepted by biologists Role of the protein molecules in this model cell membrane layers are membrane extracellular protein domains in connection to the lipid bilayer membrane. Membrane phospholipids are the molecules with hydrophillic polar heads towards the solvent such as water whereas hydrophobic tail located towards the center of the layer and this bilayer formed by micelles, as fatty acids possess one polar associated with another nonpolar head. Biological lipid bilayers are composed of phospholipids to form spontaneously into bilayers because the hydrophobic tails, which associate as "amphiphilic phospholipids" with hydrophilic phosphate head. Cell membrane possesses a property known as selective permeability. Cell membrane consists of phopholipid bilayer that also include several of the transmembrane proteins, ion channels etc. Small, non-polar molecules with hydrophobic nature diffuse more easily into the cell membrane. Similarly, proteins interact and assemble themselves to form several layers of structures in our body.

Small particles are such as oxygen and CO2, urea can cross the lipid bilayer easily through diffusion compared to glucose (channel mediated-sodium dependent transport into the cell), amino acids (channel mediated) and various ions etc. Atoms that can form hydrogen bonding or electrostatic interactions arranged in complementary fashion to create a hydrophobic pore. Within the cell membrane, the tail portions (lipid region) bonded together and the head portions (hydrophilic region) exposed into cell interior and exterior, which is very essential for the selective permeability of cell membrane. Membrane proteins can contain several transmembrane elements for example G-protein coupled receptors contain 7-transmembrane regions with helical protein subunits. These membrane proteins can occupy only one side of the membrane but majority to the internal surface & some of these proteins are in the membrane are locked into the membrane for ligand binding via other cross-linking membrane proteins or by polar phospholipid heads with ionic interactions. Majority of transmembrane poritens are three dimentional with "alpha-helical sheets" in their structure

These proteins of mosaic model possess significant characteristics in pertinent to a lot of cellular processes such as cell-cell signaling, cellular apoptosis followed by cell death, membrane budding, and biological cell fusion and division.

The considerable movement and spin orientation of the membrane phospholipids from one monolayer to other leaflet layer called “flip-flop” mechanism.

Membranes are fluid structures, and the fluidity depends on fatty acid composition and cholesterol content. The fluidity of the fatty acids increases with the degree of unsaturation and decreases with the length of the linear hydrocarbon chain.

Lipid rafts are the intermittent molecules and formed of between sphigolipids with micelles and cholesterol along with proteins and enabling the lipid bilayer thicker and the membrane proteins tend to be accumulated. According to homeoviscous theory and adaptation, the more acyl chain addition (packaging) to the long chained fatty acids in the biological phospholipids membranes associated with decreased fluidity because of the more viscosity. Long unsaturated (presence of double and triple bonds between fatty acid carbons) fatty acids with trans- configuration possess more melting temperature associated with less membrane rigidity.

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