Cell membrane

concentrations of water through a selectively permeable membrane. Osmosis is a way for water molecules to create equilibrium between a cell and its environment. For example, if the cell is a hypotonic solution and its environment is a hypertonic solution, then water will naturally diffuse to its environment to create equilibrium. The guiding question for this experiment was, “How does alcohol concentration affect the water content in cells?” It is related to osmosis because alcohol molecules are…

Evidence for and against the Davson- Danielli model of membrane structure The plasma membrane is thin and has double layers. The plasma membrane has two dark lines and a lighter central region. The two dark lines suggests the presence of the protein on either side. The lighter central region suggests the presence of phospholipids. The dark grainy appearance could be the ribosomes. Ribosomes appear as dark granules in the cytoplasm. Measured by rule: approximately 1 mm actual size 10 nm…

are proton pumps that are dependent on ATP. They are involved with processes along the plasma membrane. The processes involved are membrane traffic, protein degradation, bone resorption, tumor cell invasion, and pH homeostasis. There has been a better understanding of the structure and mechanism of V-ATPases. Another thing brought to light, are the mechanisms that occur to regulate its activity in cells. This includes the V¬1 and V0 domain assembly and the regulation of the V-ATPases. The final…

process of moving soluble molecules across a membrane is referred to as passive transport. For this type of transport chemical energy is not necessary. Two of the main types of passive transport that the human body utilizes are osmosis and diffusion. Diffusion is the movement of a hydrophobic substance across a semi-permeable membrane without the use of cell energy from a gradient area of higher concentration to an area (either inside or outside of the cell) with a lower concentration…

A receptor is a molecule usually found on the surface of the cell and receiving signals (chemical or hormonal) from outside the cell. Receptors belong to class of proteins. Binding of some substance to the receptor brings about changes that direct the actions of cell containing receptor. Ligand is the molecule that binds to the receptor and it can be a peptide, a hormone, neurotransmitter, drug or a toxin etc. Each receptor possesses two functional domains: recognition domain that binds the…

passive transport move oxygen, water, and nutrients into cells and remove waste. Active transport requires a chemical energy because it moves from lower concentration to areas of higher concentration. It uses ATP to pump the molecules against the concentration, which requires cellular of solute. Passive transport moves from areas at a higher concentration to low concentrations, so it doesn’t require energy. Active transport takes place in the membranes of both the mitochondria and chloroplasts.…

drainage of bile in the liver. This progresses to biliary fibrosis and can be fatal if left untreated in the first two years after birth. Biliary atresia is the most typical source of end-stage liver disease. A previous study was carried out to identify a cell population expressing the PROMININ-1 gene. Within periportal fibrosis, the expansion of this population was studied and was located adjacent to ductular reactions. This study utilized a mouse model that was infected with the Rhesus…

Adenosine triphosphatase (ATPase) is a mitochondrial lipid dependent membrane bound enzyme and principle donor of free energy in the living system. Any alteration in membrane lipids leads to changes in membrane fluidity, which in turn alters the ATPase activity and cellular function. The use of ATPase level measurement was considered as an appropriate index of membrane damage. Pathological processes that interfere with the production of ATP may interfere with sodium pump activity, which in turn…

fact that this “limits communication between cells, a condition that probably accounts for the vastly decreased ability of prokaryotes to form multicellular organisms.” This is compared to the internal skeleton strucutre of Eukaryotes, where “it is formed by a complex of protein tubules called the cytoskeleton.” (K S Kabnick and D A Peattie, 1991.) This difference in structure gives a pliable membrane to the cell rather than a rigid cell wall. This increases mobility of many…

(Kövecses 91) the biological function of cell membranes through the underlying descriptive structural megametaphors CELL MEMBRANE IS A WALL and TRANSPORT PROTEINS ARE DOORS and the mappings between them, and by “hiding” (Kövecses 92) other aspects of this concept. Throughout this chapter, Peter Raven and George Johnson pair these main conceptual metaphors with visual portrayals of transport proteins that enable molecules to pass through the “wall” of the cell, in order to develop a stronger…