Also, in considering osmosis, it is important to understand that we are comparing the solution outside the cell (A) to the solution inside the cell (B). In other words, we compare the solutions on either side of the membrane.
When a blood cell is placed into a solution with a concentration of 0.9% salt, the solutions inside and outside of the cell are isotonic to each other. Water moves into and out of the cell at an equal rate. The cell is not affected by this solution. It remains normal and functional .
When a blood cell is placed in a 10% salt solution, the outside solution is hypertonic to the solution inside the cell. The solution inside the cell is hypotonic to the outside solution. Water will move out of the cell at a faster rate than it moves into the cell.
When an animal cell is placed in distilled water, the solution inside the cell is hypertonic to the outside solution. The outside solution is hypotonic to the solution inside the cell. Water moves into the cell at a faster rate than it moves out.
In general, the size of the cell does not change because the cell wall is rigid and does not collapse. However, in this condition, the cells have no pressure to hold up the leaves of the plant . It wilts.
Unlike passive transport, active transport does require an input of energy from the cell .
Another important difference between active and passive transport mechanisms is that active transport can move particles against the concentration gradient , from an area of lesser concentration to an area of greater concentration.
In situations where the cell needs to take in all the particles it can despite concentration, it is important to have this option.
As you take in and digest nutrients, the cells that absorb the nutrients may start out with a lesser concentration, but as more and more move into the cell, the concentration becomes greater inside the cell, but the cell still needs to continue taking in more.
Co-transport is similar to typical active transport except, in this case, a second type of particle attaches itself to the original particle and both are pulled through the membrane at the same time (piggyback).
Cells like your white blood cells often take in bacterial cells to protect you from infection. Other cells (especially unicellular organisms or protozoa) take in small cells as food . In order to bring in a complete cell, the cell membrane rises up, surrounds and engulfs the cell.
Also, phagocytosis may bring in large chunks of materials like splinter fragments .
The process of releasing vacuole-encased molecules from the inside of the cell is called Exocytosis. The vacuole is formed within the cell and then fuses with the cell membrane as it releases its contents.
If Enzyme 3 is present, D will be converted to F and G the original pathway will be completed with these final products. But if Enzyme 4 is present D will be converted to W and X and the alternate pathway will occur, resulting in the final products Y and Z. Enz 4 Enz 5 Enz 1 Enz 2 Enz 3 + + + A + B F + G D + E C + W + X Y + Z +
Apoenzyme = protein part of the enzyme Coenzyme (organic) or cofactor (inorganic) = non-protein part of the enzyme Active Site = where the substrate fits into the enzyme Allosteric site = where the enzyme is activated or deactivated enzyme
An enzyme may be inhibited by placing an inhibitor molecule into the allosteric site . This process causes the shape of the active site to change so that the substrate can no longer fit into the active site.
The peak of the curve represents the optimal temperature. This is the temperature at which the reaction rate is fastest.
As temperature cools from optimal, molecules slow down and do not encounter each other as often or with as much energy, so the reaction rate slows down until the reaction no longer occurs. This temperature is called the minimal temperature .
As temperature becomes warmer than optimal, enzymes begin to change shape. This change in shape is called denaturing the enzyme.
If the temperature gets too warm, the enzyme changes so radically that the substrate can no longer fit into the active site. The reaction rate is then 0 (no reaction occurs) and the enzyme is irreversibly denatured.
Among mammals, smaller mammals tend to have higher normal body temperatures than larger mammals. As a result, one would expect the optimal temperature for a small mammal to be at a higher temperature than the optimal for larger mammals.
The concentration profile for enzymes is quite different than the temperature and pH profiles.
Initially, there is a steep positive correlation between enzyme concentration and reaction rate, but at a certain point, using more enzyme cannot make the rate go faster and the curve levels off into a plateau.
There is no minimal or maximal concentration. The optimal concentration occurs just before the plateau .