Which organelle controls osmotic pressure in a cell

Osmosis is the spontaneous net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves across a semipermeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Osmosis can be made to do work.Osmotic pressure is defined as the external pressure required to be applied so that there is no net movement of solvent across the membrane. Osmotic pressure is a colligative property, meaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity.Osmosis is a vital process in biological systems, as biological membranes are semipermeable. In general, these membranes are impermeable to large and polar molecules, such as ions, proteins, and polysaccharides, while being permeable to non-polar and/or hydrophobic molecules like lipids as well as to small molecules like oxygen, carbon dioxide, nitrogen, and nitric oxide. Permeability depends on solubility, charge, or chemistry, as well as solute size. Water molecules travel through the plasma membrane, tonoplast membrane (vacuole) or protoplast by diffusing across the phospholipid bilayer via aquaporins (small transmembrane proteins similar to those responsible for facilitated diffusion and ion channels). Osmosis provides the p...

Plants - Higher plants use the stomata on the underside of leaves to control water loss. Plant cells rely on vacuoles to regulatecytoplasm osmolarity. Plants that live in hydrated soil (mesophytes) easily compensate for water lost from transpiration by absorbing more water. The leaves and stem of the plants may be protected from excessive water loss by a waxy outer coating called the cuticle. Plants that live in dry habitats (xerophytes) store water in vacuoles, have thick cuticles, and may have structural modifications (i.e., needle-shaped leaves, protected stomata) to protect against water loss. Plants that live in salty environments (halophytes) have to regulate not only water intake/loss but also the effect on osmotic pressure by salt. Some species store salts in their roots so the low water potential will draw the solvent in via Osmoregulation in Humans In humans, the primary organ that regulates water is the kidney. Water, glucose, and amino acids may be reabsorbed from the glomerular filtrate in the kidneys or it may continue through the ureters to the bladder for excretion in urine. In this way, the kidneys maintain the electrolyte balance of the blood and also regulate blood pressure. Absorption is controlled by the hormones aldosterone, antidiuretic hormone (ADH), and angiotensin II. Humans also lose water and Osmoreceptors in the hypothalamus of the brain monitor changes in water potential, controlling thirst and secreting ADH. ADH is stored in the pituitary gla...

Learning Objectives By the end of this section, you will be able to: • Describe the structure and function of the cellular organelles associated with the endomembrane system, including the endoplasmic reticulum, Golgi apparatus, and lysosomes • Describe the structure and function of mitochondria and peroxisomes • Explain the three components of the cytoskeleton, including their composition and functions Now that you have learned that the cell membrane surrounds all cells, you can dive inside of a prototypical human cell to learn about its internal components and their functions. All living cells in multicellular organisms contain an internal cytoplasmic compartment, and a nucleus within the cytoplasm. Cytosol, the jelly-like substance within the cell, provides the fluid medium necessary for biochemical reactions. Eukaryotic cells, including all animal cells, also contain various cellular organelles. An organelle (“little organ”) is one of several different types of membrane-enclosed bodies in the cell, each performing a unique function. Just as the various bodily organs work together in harmony to perform all of a human’s functions, the many different cellular organelles work together to keep the cell healthy and performing all of its important functions. The organelles and cytosol, taken together, compose the cell’s cytoplasm. The nucleus is a cell’s central organelle, which contains the cell’s DNA ( Figure 3.13 Prototypical Human Cell While this image is not ...

Have you ever forgotten to water a plant for a few days, then come back to find your once-perky arugula a wilted mess? If so, you already know that water balance is very important for plants. When a plant wilts, it does so because water moves out of its cells, causing them to lose the internal pressure—called turgor pressure—that normally supports the plant. Why does water leave the cells? The amount of water outside the cells drops as the plant loses water, but the same quantity of ions and other particles remains in the space outside the cells. This increase in solute, or dissolved particle, concentration pulls the water out of the cells and into the extracellular spaces in a process known as osmosis. Formally, osmosis is the net movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. This may sound odd at first, since we usually talk about the diffusion of solutes that are dissolved in water, not about the movement of water itself. However, osmosis is important in many biological processes, and it often takes place at the same time that solutes diffuse or are transported. Here, we’ll look in more detail at how osmosis works, as well as the role it plays in the water balance of cells. This is actually a complicated question. To answer it, let’s take a step back and refresh our memory on why diffusion happens. In diffusion, molecules move from a region of higher concentration to one of lower c...

What is osmoregulation? Doctors typically recommend drinking eight to ten glasses of water a day. This amount is necessary for the proper balance of electrolytes in the human body. The intake is balanced by more or less equal excretion of fluids by urination, defecation, sweating, and, to a lesser extent, respiration. The body’s organs and tissues are immersed in fluid at a constant temperature, pH, and solute concentration, each of which contributes to maintaining the body’s homeostasis. The solutes in body fluids are mainly mineral salts and sugars. Osmotic regulation, or osmoregulation, keeps these solutes at the ideal concentrations. Osmotic homeostasis is maintained despite the influence of external factors such as temperature, diet, and weather conditions. Osmosis is the diffusion of water across a membrane in response to osmotic pressure caused by an imbalance of molecules on either side of the membrane. Osmoregulation is the process of maintenance of salt and water balance (osmotic balance) across membranes within the body’s fluids, which are composed of water plus electrolytes and non-electrolytes. An electrolyte is a solute that dissociates into ions when dissolved in water. A non-electrolyte, in contrast, does not dissociate into ions during water dissolution. Both electrolytes and non-electrolytes contribute to the osmotic balance. The body’s fluids include blood plasma, the cytosol within cells, and interstitial fluid, the fluid that exists in the spaces betwe...