The importance of diffusion in living organisms?

Answer 1

Diffusion is the net movement of molecules from an area or high concentration, to an area of lower concentration. It is therefore said to happen down a concentration gradient. No energy in the form of ATP is used in transporting the molecules; it is simply a natural random movement. Diffusion ends when the molecules reach a state at which they produce no net movement, this is called equilibrium. The rate of diffusion is controlled by fick's law; Diffusion is important to plants, which need to diffuse in CO2, and diffuse out O2 during photosynthesis. Plants have specially adapted gas exchange surfaces for this very reason. Air enters the stomata, at which point CO2 diffuses into the plant, due to the concentration gradient maintained by the use of CO2 in the photosynthesis reaction in the plant. At this point O2 also diffuses out down a concentration gradient, as a waste product of photosynthesis. The gasses diffuse through the internal spongy mesophyll inside the stomata, which is a hollow to provide a larger surface area for diffusion at a greater rate. Mammals have another specially adapted exchange surface called the lungs. The lungs have a large internal structure, packed with millions of alveoli - small sacks of air. The lungs are ventilated to maintain their concentration gradient, which draws in fresh air with a higher concentration of O2. The air then fills the alveoli, which are completely surrounded by many blood capillaries in order to maintain a short diffusion distance for the O2 to diffuse in, and the CO2 to diffuse out, both down concentration gradients. The blood then carries the Oxygen away, and cycles the CO2 back, maintaining a strong concentration gradient, helping to raise the diffusion rates. It is by this mechanism that mammals are able to maintain respiration in all the cells of their body. Insects have no blood supply to carry respiratory gasses throughout their bodies, and so they rely on openings called spiracles to diffuse air into, replenishing their oxygen source. Many larger insects actively ventilate their respiratory systems, by raising and lowering the volumes of their abdomens with muscle contractions. After the air has diffused through the spiracle, it travels into trachea, which is impermeable to gas and water diffusion. From here it diffuses into tracheoles, which are permeable to gasses and water. The respiratory gasses then exchange, and the new supply of O2 is delivered down a concentration gradient directly into the cells themselves. Fish have a special exchange chamber called an operculum. The operculum in a fish is filled with very vascularised gills, which is the site of gas exchange. A fish draws in a fresh supply of oxygenated water through its mouth, which it then puts under positive pressure by forcing the floor of the mouth to raise. This forces the water out over the gills, increasing the rate of diffusion by replenishing the source of O2, and therefore the concentration difference. The gills have a very high surface area because they are comprised of thousands of tiny filaments, or gill plates. Diffusion is also increased because the blood supply flows in the opposite direction to the water through the opercular cavity, called counter current flow. This ensures that there is always an effective concentration difference at every part of the gill, and so diffusion can happen right across the gill. Diffusion is also very important in the conduction of nerve impulses. Ions are charged molecules, and therefore they cannot diffuse through the plasma membranes of cells. This means that they need special extrinsic cell surface proteins called carrier proteins in order to be able to diffuse into the cell. These proteins can be gated, so that the influx and efflux can be controlled. In the case of nerve impulses, these gates at resting potential are closed. The resting potential is maintained by the active transport of sodium out of the axon, and phosphate ions in. This maintains a large concentration gradient from the inside of the axon to the outside. As a result of this, when an action potential is required to start, the sodium gates are opened, and sodium ions flood in down a concentration gradient. This causes the membrane potential to rise to +40mv, from the resting potential of -70mv. Diffusion is also very important to the processes involved in synapse transmission. Synapses receive action potentials, and transmit across gaps or clefts from one synapse to another. They are necessary for many reasons, such as to ensure impulses are unidirectional, and to filter out low frequency impulses. To transmit an impulse, first the calcium gates in the presynaptic node open. This causes calcium ions to enter via diffusion down a concentration gradient, which in turn triggers vesicles filled with transmitter substance to migrate to the membrane and fuse with it, releasing it into the cleft. The transmitter substance then diffuses across the cleft, to the post synaptic node, then fuses with receptors on its surface. The receptors on the surface of the post synaptic node cause the opening of the sodium gates, as happens in a normal action potential. Water is a special case of diffusion. Water diffusion is called osmosis and can be controlled a lot more variably by solutes adjusting the water potential of an area. This means the area will have a higher affinity to absorb or take on more water if it has a greater number of solutes in it, or a lower water potential. This helps organisms in many ways, including in the kidneys of mammals. Within the kidney, osmosis is required to reabsorb water from being lost in urine. In order to do this, the kidney has thousands of nephrons. The main point of the nephron is to be able to filter out undesirable substances in blood, without losing water or useful molecules such as glucose. In order to do this, many diffusion and osmosis based processes take place. Water is reabsorbed from the collecting duct by the action of sodium ions outside of the duct. These ions lower the water potential outside of the collecting duct, so water has a higher tendency to leave via osmosis. This osmosis is controlled by the hormone ADH changing the permeability of the collecting duct to water, dependant on the water requirements of the body.

Answer 2

The movement of atoms and molecules from higher concentration to lower concentration is known as diffusion.

Diffusion is important for living things for example if a plant is realeasing oxygen through diffusion it can spread in all directions if there was no diffusion people would had to go to plants to breathe. Our cells also take oxygen from air because in air oxygen is at a higher concentration and in cells at a lower concentration.

Answer 3

sugar in your gut,

oxygen to breath (respiration)

Photosynthesis

Answer 4

Diffusion is important to organisms because it makes sure that not too much of a molecule enter the cell beacause a persons inernal homeostasis needs to stay stable.

Answer 5

i dont know u stink