Buffers are chemicals that help a liquid resist changing its acidic properties when other chemicals are added that will normally cause a change in these properties. Buffers are essential for living cells. This is because buffers maintain the right pH of a liquid. What is pH? It's a measure of how acidic a liquid is. For example, lemon juice has a low pH of 2 to 3 and is very acidic -- so is the juice in your stomach that breaks down food. Since acidic liquids can destroy proteins, and cells are chock-full of proteins, cells need to have buffers inside and outside them in order to protect their protein machines. The pH inside a cell is about 7, which is considered neutral like pure water.
What Is A Buffer?
The opposite of a chemical that is an acid is a chemical that is a base, and both can exist in a liquid. An acid releases a hydrogen ion into a liquid, while a base takes a hydrogen ion out of the liquid. The more free-floating hydrogen ions there are in a liquid, the more acidic that liquid becomes. Thus acids make a liquid more acidic, and bases make a liquid more basic -- basic is another way of saying less acidic. Buffers are chemicals that can easily release or take up hydrogen ions in a liquid, meaning they are able resist a change in pH by controlling how many free-floating hydrogen ions there are. The pH scale ranges from 0 to 14. A pH from 0 to 7 is considered acidic and a pH from 7 to 14 is considered basic. A pH of 7, in the middle, is neutral and is pure water. Different buffers maintain different pHs, but the ones inside a cell maintain a pH of around 7.2.
Protect Against Accidental Spills
Animal cells contain pouches called lysosomes. These pouches are the recycling center of the cell. The insides of these pouches are acidic, having a pH of 5, and contain many enzymes that digest proteins, fats, sugars and DNA. The acidic environment inside a lysosome helps break down molecules for recycling. However, if one or more of these pouches accidentally breaks open inside the cell, the acidic contents will spill into the rest of the cell and make the whole cell acidic. The cell has buffers that protect itself in case these spills happen. Since buffers resist a change in pH, a few lysosomes that break open will not make the pH inside a cell more acidic.
pH Affects Protein Shape
The danger of a change in pH inside a cell is that pH dramatically affects the structure of proteins. The cell is made of many different types of proteins and each protein only works when it has its proper three-dimensional shape. The shape of a protein is held in place by attractive forces inside the protein, like many mini-magnets here and there that connect to hold the whole protein in place. Some of these magnets will lose their magnetic power if the pH changes. Therefore, if the inside of a cell gets too acidic or too basic, then proteins begin to lose their shape and no longer work. The cell becomes like a factory without workers and without repairmen. Therefore, buffers inside a cell prevent this from happening.
Changing The pH Can Make Stem Cells
In 2014, the journal “Nature” reported a very exciting discovery from Japanese stem-cell researchers. Normal adult cells such as skin cells and brain cells can be turned into stem cells when placed in an acidic environment. Stem cells are cells that have the potential to become any type of cell in the body, which makes them very promising as cures for medical problems. Dead, missing, or broken cells can be replaced by new cells. Stem cells can be taken from a crushed embryo, which is very controversial when it comes to human embryos, so being able to turn adult cells into stem cells is an exciting step for biomedical science. What this study tells us is that buffers inside a cell also likely prevent the cell from forgetting its adult identity and becoming a stem cell.
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