Discuss the role of proteins in membrane structure and transport of molecules across the membrane? (AP Biology II Free Response Question) Solution 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, diffusion of nutrients across the membrane into & out of the cell finally to attain homeostasis 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 biol.

1. Discuss the role of proteins in membrane structure and transport of molecules across the
membrane? (AP Biology II Free Response Question)
Solution
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, diffusion of nutrients across the membrane into &
out of the cell finally to attain homeostasis
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

2. 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.