The Outer Membrane

The endoplasmic reticulum is specialised for protein processing and lipid biosynthesis. One of its primary functions is to regulate the ionic concentration in the cytoplasm via the movement of Ca2+, via ionic pumps and channels. It also contains enzymes responsible for the metabolising of drugs. Endoplasmic reticulum (ER) can come in two forms. As depicted in Fig. 2 Rough ER has ribosomes present as part of the membrane of the organelle, and together with these ribosomes takes polypeptides and amino acids from the cytosol and synthesises proteins destined for attachment to cell membranes. It is in the lumen of the rough ER that the proteins are folded into the specific three dimensional shapes that are so important for biochemical recognition and linking sites [6]. It is called rough because of the presence of ribosomes makes the surface of the membrane look rough, unlike smooth ER, which lacks the ribosomes so the membrane looks smooth. Rough ER is composed of a large but convoluted flattened sac. The main function of the smooth ER is the production of lipids and the metabolism of compounds (such as the breakdown of glycogen into glucose). Because of the different functions between the rough and smooth ER, different specialised cells will have different amounts of each; for example, hepatic

Mitochondria and chloroplasts have two membranes that surround them. The inner membrane is probably from the engulfed bacterium and this is supported by that the enzymes and proteins are most like their counterparts in prokaryotes. The outer membrane is formed from the plasma membrane or endoplasmic reticulum of the host cell. The electron transport enzymes and the H+ ATPase are only found in the mitochondria and chloroplasts of the eukaryotic cell. (2)

Introduction: The biological membranes are composed of phospholipid bilayers, each phospholipid with hydrophilic heads and hydrophobic tails, and proteins. This arrangement of the proteins and lipids produces a selectively permeable membrane. Many kinds of molecules surround or are contained within

The lipids found in the membrane are known as phospholipids. Phospholipids are fat derivatives in which one fatty acid has been replaced by a phosphate group and one of several nitrogen-containing molecules. The phospholipids’ structure is such that it appears to have a ‘head’ attached to a ‘tail’. The head section of the lipid is made of a glycerol group which is then attached to an ionised

The cell membrane consists of eight distinctive parts that each have their own unique structure and function. The phospholipid bilayer is an integral part of the cell membrane because it is the external layer of the cell membrane and composes the barriers that isolate the internal cell components and organelles from the extracellular environment. It is composed of a series of phospholipids that have a hydrophobic region and a hydrophilic region. These regions are composed of the hydrophilic heads and the hydrophobic tails of the phospholipids, this organization of the polar heads and nonpolar tails allows the heads of the cell to form hydrogen bonds with water molecules while the tails are able to avoid water. The phospholipid bilayer also has many important functions within the cell, it gives the cell shape, provides protection, and it is selectively permeable which allows it to only let very specific molecules pass through its surface. The phospholipid bilayer is an important structure because it prevents harmful and unwanted molecules from entering the cell and isolates organelles which helps to maintain the internal environmental homeostasis of the cell.

7. List several functions for the outer membrane in gram-negative bacteria. What is the chemical composition of the outer membrane?

“While motility is commonplace among the prokaryotes, it is important to note the variety of structures responsible for motility. These structures vary depending not only on the organism in question, but also on the particular environment” (Bardy, Ng, & Jarrell, 2003). “Study of the bacterial flagellum has provided insights into many aspects of prokaryotic cellular activities including genetics and regulation, physiology, environmental sensing, protein secretion and assembly of complex structures” (Bardy, Ng, & Jarrell, 2003). “Continued study of all prokaryotic motility structures will provide knowledge that is likely to reach far beyond the topic of motility and pathogenicity” (Bardy, Ng,

Introduction: Cell membranes contain many different types of molecules which have different roles in the overall structure of the membrane. Phospholipids form a bilayer, which is the basic structure of the membrane. Their non-polar tails form a barrier to most water soluble substances. Membrane proteins serves as channels for transport of metabolites, some act as enzymes or carriers, while some are receptors. Lastly carbohydrate molecules of the membrane are relatively short-chain polysaccharides, which has multiple functions, for example, cell-cell recognition and acting as receptor sites for chemical signals.

Gram negative and gram positive bacteria differ from each other in many ways especially in the composition and size of their cell walls. Unlike Gram-positive bacteria, Gram-negative bacteria have a thin peptidoglycan layer surround by an outer membrane. This outer membrane contains many proteins one of them being lipopolysaccharides (LPS), which contributes to the bacteria’s negative charge. One part of this protein is a lipid, called Lipid A, which is considered an endotoxin because this lipid triggers an immune response stimulating fever

Strains of Escherichia coli and Citrobacter rodentium contain set of operons called the locus enterocyte effacement (LEE) region in their genomes. This region encodes a type III secretion system (T3SS).

The smooth ER does not have any ribosomes on it's membrane. It's functions can vary depending on the differences of the cell it is located in. The smooth ER makes lipids, breaks down carbohydrates, and detoxifies substances that may be harmful to the cell.

To study the effects of hypotonic, hypertonic and isotonic solutions on plant and animal cells.

Bacteriorhodopsin is a globular protein, (Henderson, 1975) which acts as a light driven proton- pump located in the native purple membrane of Halobacterium halobium. It was first discovered by Stoechenius and his lab in 1979 (Stoeckenius, 1979). Although Henderson and Unwin had already made a three-dimensional map of the purple membrane at 7Å ,by electron microscopy and diffraction, four years prior to Stoechenius (Henderson, 1975). Studying Bacteriorhodopsin by multidimensional solution NMR methods has confirmed that they were corrected in their predicted secondary structure. Since then decades of intensive research has gone into discovering more about Bacteriorhodopsin and vast advances in our knowledge have occurred but there are still gaps in our understanding. Bacteriorhodopsin has a vital role in H.halobium as the bacteria uses the energy generated by the electrochemical gradient to provide energy for the synthesis of ATP as well as other metabolic processes (Khorana, 1988). ATP is used by the bacterium to power its flagella. The electrochemical gradient is formed by pumping protons into the extracellular space. It is found as a high density two-dimensional crystal lattice within the purple membrane, making it possible to study as crystals don’t need to be formed because they naturally occur. The space group of the two-dimensional lattice is P3 (Kyte, 1995). The molecular weight of the Bacteriorhodopsin is 26,000, which is approximately 75% of the total

The bacterium evolved by loosing its genes converting it from a free-living microbe into a pathogen. It needs the host’s nutrients in order to survive. The bacterium latches itself onto the host epithelial cells by a 160 kDa type 1 pilli. The pilli, located on a specific organelle on the polar region of the

In all areas of biology, it is easy to see that structure is related to function. This statement holds true in microbiology as well, the study of microorganisms, including bacteria. One characterizing feature of bacteria is the cell wall, which can generally (although not in all situations) be categorized into one of two categories: either Gram positive or Gram negative. Gram positive bacteria’s cell walls are composed of a large peptidoglycan layer (up to 90% of their cell wall). Within this large peptidoglycan layer, one can find techoic acids, which contribute to the maintenance of cell wall structure, and lipotechoic acids, which attach to membrane lipids. Gram positive bacteria that act as pathogens can also potentially release exotoxins, which can have very dangerous effects on humans. Gram negative bacteria, on the other hand, have a very small layer of peptidoglycan in their cell wall, which is surrounded by an outer membrane. Within the outer membrane, one can find the lipopolysaccharide layer, which is one of the most distinguishing factors of Gram-negative bacteria. It is important to note that Gram negative bacteria fail to possess techoic