What are Buffers?
Below are some notes on buffers that can be used for an understanding or refresher that is helpful and useful for the sciences; specifically biology, chemistry, and biochemistry.
What is a Buffer?
Buffer/ Buffer Solution = a solution that resists changes in pH when small to medium amounts of a strong acid or a strong base are added. This solution is made up of a weak acid and its conjugate base.
-Buffers are important and critical to life.
-Buffers are both naturally occurring and can be synthesized in the laboratory.
An example of a naturally occurring buffer is the buffering system in blood that based on the dissociation of carbonic acid (H2CO3).
H2CO3 <--> H+ + HCO3-
How Do Buffers Work?
The way buffers interact is dependent upon the characteristics of the weak acids and the conjugate bases that are in the buffer.
Depending on whether [OH-] or [H+] is added to the solution, the conjugate base or the weak acid will form.
When [OH-] or [H+] are added, they are "used up" when adding it to a buffer. By doing this, the pH is able to maintain some stability and the pH maintains more stability than if the same acid or base had been added to a solution that did not have a buffer.
Buffer Effects
To Buffer Solution:
| Adding [H+]
| Adding [OH-]
|
|---|---|---|
Reacts:
| w/conjugate base
| w/weak acid
|
Forms:
| the weak acid
| water + conjugate base
|
How to Figure Out the Effect of a Buffer?
When buffer is added, the new pH can be calculated using the values of the acid concentration and the conjugate base concentration in the Henderson-Hasselbach equation (referenced in "Notes on Acids, Bases, and pH").
How Are Buffers Selected?
Buffers are selected based on the optimal pH range that needs to be maintained and what will be given off and used up in the buffer.
pH Values and Base/Acid Ratios for Buffers
If the pH equals:
| The ratio of base form/acid form equals:
|
|---|---|
pKa -3
| 1/1000
|
pKa -2
| 1/100
|
pKa -1
| 1/10
|
pKa
| 1/1
|
pKa +1
| 10/1
|
pKa +2
| 100/1
|
pKa +3
| 1000/1
|
This table is based off of Table 2.7 in "Biochemistry" by Mary K. Campbell and Shawn O. Farrel; 7th edition.
High buffering capacity= buffer solution that contains greater amounts of both acid and base.
Low buffering capacity= buffer solution that contains low concentrations of both acid form and base form.
What is Buffering Capacity?
Buffering capacity=how much concentrations of acid and/or base a buffer is able to form.
Zwitterions=compounds that have both a positive and negative charge, and are electrically neutral in solution.
Zwitterions and Buffer Use
Zwitterions can be used as buffers. In use, they are not as likely to affect the biochemical reactions than when using other buffers.
Other Hubs in My "Notes On..." Series
Source Information
The information used for this hub was taken from the following sources:
"Biochemistry" by Mary K. Campbell and Shawn O. Farrel; 7th edition.
My biochemistry lectures at school.
Knowledge and notes taken from previous courses in chemistry and biology.
