movement of molecules

movement of molecules

lungs

diffusion

by: alya

Diffusion is the movement of molecules from an area of high concentration of the molecules to an area with a lower concentration.

diffusion occurs in the lungs -> Oxygen is needed to sustain cells in organs, but carbon dioxide is toxic. These gases enter and exit the body through the lungs by diffusion. The lung is a network of branching and narrow tubes that starts at the trachea, or windpipe. At the tip of the narrowest tubes are grape-like clusters called alveoli. These alveolar sacs are surrounded by a net of small blood vessels. Oxygen gas diffuses from the alveolar sacs into the blood vessels, while carbon dioxide goes from the blood into the alveoli.

how the movement of molecules helps diffusion

3 examples of diffusion in the human body

surface area

intestine

Surface area and thickness of the plasma membrane: Increased surface area increases the rate of diffusion, whereas a thicker membrane reduces it.

The kinetic energy of the molecules results in random motion, causing diffusion. In simple diffusion, this process proceeds without help of a transport protein. it is the random motion of the molecules that causes them to move from an area of high concentration to an area with a lower concentration.

why gases and solutes need to diffuse

Calcium ions are essential for nerves to send signals and for skeletal muscles to contract. Calcium is stored and released from bones, but new calcium must be absorbed from food. The small intestine is the organ that absorbs new calcium. When calcium levels in the blood are low, the parathyroid gland releases parathyroid hormone, which causes the bones to release calcium and causes the small intestine to absorb calcium. The absorption of calcium in the small intestine is an example of diffusion.

how things affect diffusion

distance traveled

Gas particles often go through diffusion because they have kinetic energy Diffusion is faster at higher temperatures because the gas molecules have greater kinetic energy.

Distance traveled: The greater the distance that a substance must travel, the slower the rate of diffusion. This places an upper limitation on cell size. A large, spherical cell will die because nutrients or waste cannot reach or leave the center of the cell. Therefore, cells must either be small in size, as in the case of many prokaryotes, or be flattened, as with many single-celled eukaryotes.

temperature

plant tissues hypotonic

Higher temperatures increase the energy and therefore the movement of the molecules, increasing the rate of diffusion. Lower temperatures decrease the energy of the molecules, thus decreasing the rate of diffusion.

When the plant cell is placed in a hypotonic solution , it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting. The plant cell is said to have become "turgid" (swollen and hard.) The pressure inside the cell rises until this internal pressure is equal to the pressure outside. This liquid or hydrostatic pressure called the turgor pressure prevents further net intake of water

isotonic

root hair cells

hypertonic

hen a plant cell is placed in an isotonic solution, a phenomenon called incipient plasmolysis is said to occur. "Incipient" means "about to be". Although the cell is not plasmolsysed, it is not turgid. When this happens the green parts of the plant droop and are unable to hold the leaves up into the sunlight.

active transport

The root hair cells have carrier proteins in their cell membranes. These pick up the mineral ions and move them across the membrane into the cell against the concentration gradient.

Active transport is a kind of cellular transport where substances move against a concentration gradient. This means that the direction is from an area of lower concentration to an area of higher concentration.

hen a plant cell is placed in a hypertonic solution , the water from inside the cell�s cytoplasm diffuses out and the plant cell is said to have become "flaccid". If the plant cell is then observed under the microscopic, it will be noticed that the cytoplasm has shrunk and pulled away from the cell wall .This phenomenon is called plasmolysis. The process is reversed as soon as the cells are transferred into a hypotonic solution (deplasmolysis).

kidneys

the function of the kidney is to filter out salts and waste products from the bloodstream. These molecules are collected as urine, which is excreted from the body. The kidney contains many microscopic filtration systems called nephrons, which are microscopic tubes is shaped like a U. Each portion of the U diffuses different molecules, such as water and salt. Whatever gets through the entire U will go into another tube, called the collecting duct, and eventually to the bladder. The collecting duct is the last chance for the nephron to take water out of urine by diffusion.

isotonic

osmosis

Hypotonic

hypertonic

A solution is isotonic when its effective osmole concentration is the same as that of another solution.

the tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane.

Hypertonic means that the environment outside of the cell has a higher concentration of solutes than the cell itself. That will attract water molecules from the cell leading to the shrinking of the cell.

A hypotonic solution is a solution that has a lower solute concentration compared to another solution. Hypotonic is a description of the solute content of one solution in relation to another solution. It is used to help scientist describe cells