Biology question?

Question

What is a buffer and how does it regulate pH?

Answer 1

Buffering agents can be either the weak acid or weak base that would comprise a buffer solution. Buffering agents are usually added to water to form buffer solutions. They are the substances that are responsible for the buffering seen in these solutions. These agents are added to substances that are to be placed into acidic or basic conditions in order to stabilize the substance. For example, buffered aspirin has a buffering agent, such as MgO, that will maintain the pH of the aspirin as it passes through the stomach of the patient. Another use of a buffering agent is in antacid tablets, whose primary purpose is to lower the acidity of the stomach.

The way buffering agents work is seen in how buffer solutions work. Using Le Chatelier's principle we get an equilibrium expression between the acid and conjugate base. As a result we see that there is little change in the concentrations of the acid and base so therefore the solution is buffered. A buffering agent sets up this concentration ratio by providing the corresponding conjugate acid or base to stabilize the pH of that which it is added to. The resulting pH of this combination can be found by using the Henderson-Hasselbalch equation:

pH = pKa+ log[10] [A-]/[HA]

where HA is the weak acid and A is the anion of the base.

Answer 2

a buffer is usually a weak acid and it helps to regulate pH by forming with the dissociated electrolytes in the strong acid.

let's say HCl is the strong acid. I'm not sure what it is for this particular acid, but lets say that it dissociates (which gives it its acidic power) into H+ and Cl- in a 50-50 split. well, if you add a weak acid, the weak acid binds to the H+ and Cl- and "uses up" some of the strong acid. then what's left of the strong acid still dissociates 50-50, but there is less of it in the same amount of solution. Viola! the buffer (the weak acid) has reduced the pH of the solution.

If you have an upset stomach, it is usually due to increased acidity, and a lot of stomach soothing remedies are weak acids to buffer the acidity in your stomach

Answer 3

A buffer is any solution that contains a weak acid and its conjugate base in similar concentrations. When a small amount of a strong acid is added to the buffer solution, some of the added protons react with the conjugate base forming an additional amount of the weak acid. Similarly, when a small amount of a strong base is added to the solution, the weak acid neutralizes some of that added base, forming an additional amount of the conjugate base of the weak acid. In either case, the effect of the added acid or base is minimized.

The Henderson-Hasselbalch equation quantitatively describes the behavior of a buffer solution. The equation is:

pH = pKa + log ([base]/[acid]) where pKa is the negative log of the acid dissociation constant for the weak acid and [acid] and [base] are the molar concentrations of the weak acid and its conjugate base.

Answer 4

In general, to buffer is to isolate or minimize the effects of one thing on another.

Buffer can refer to:

Buffer state, a country lying between two potentially hostile greater powers, thought to prevent conflict between them
Buffer zone, any area that keeps two or more other areas distant from one another, may be demilitarized
Buffer (rail transport), a device that cushions the impact of vehicles against each other
Buffer stop (bumper in U.S.), a device to prevent railway vehicles from going past the end of a section of track
Recoil buffer, an accessory for firearms, to cushion the impact of recoil
Film loop, isolates intermittent motion in a movie projector
Buffer (navy), the colloquial term for the senior seaman sailor in a (British Commonwealth) Navy ship
In chemistry:

Buffer solution, a solution which resists change of pH upon addition of small amounts of acid or base, or upon dilution
Buffering agent, the weak acid or weak base in a buffer solution
Buffer gas, an inert or nonflammable gas
Lysis buffer, in biochemistry, a destructor of cell membranes that enables analysis of the compounds within
In geology:

Mineral redox buffer, a mineral assemblage which stabilises oxidation state in natural rock systems
In electronics and computer science:

Buffer (computer science), memory used to temporarily store output or input data
Buffer (telecommunication), a routine or storage medium used to compensate for a difference in rate of flow of data between devices
Optical buffer, a device that stores optically transmitted data without converting it to the electrical domain
Buffer amplifier (also sometimes simply called a buffer), an isolating circuit used in electronics or telecommunications
Buffer (optical fiber), a component used to encapsulate one or more optical fibers in a fiber optic communication cable
Vacuum column, isolates intermittent motion in a Magnetic tape drive
In MMORPG:

Buff (MMORPG terminology), common title for character classes which primary function is to enhance other character's abilities (most often in some magic way).
People

Bruce Buffer, sports announcer.
Michael Buffer, sports announcer.
Buffer solutions are solutions which resist change in hydronium ion and the hydroxide ion concentration (and consequent pH) upon addition of small amounts of acid or base, or upon dilution. Buffer solutions consist of a weak acid and its conjugate base (more common) or a weak base and its conjugate acid (less common). The resistive action is the result of the equilibrium between the weak acid (HA) and its conjugate base (A-):

HA(aq) + H2O(l) ⇌ H3O+(aq) + A-(aq)
Any alkali added to the solution is consumed by hydronium ions. These ions are mostly regenerated as the equilibrium moves to the right and some of the acid dissociates into hydronium ions and the conjugate base. If a strong acid is added, the conjugate base is protonated, and the pH is almost entirely restored. This is an example of Le Chatelier's principle and the common ion effect. This contrasts with solutions of strong acids or strong bases, where any additional strong acid or base can greatly change the pH.

When writing about buffer systems they can be represented as salt of conjugate base/acid, or base/salt of conjugate acid. It should be noted that here buffer solutions are presented in terms of the Brønsted-Lowry notion of acids and bases, as opposed to the Lewis acid-base theory (see acid-base reaction theories). Omitted here are buffer solutions prepared with solvents other than water.

Contents [hide]
1 Calculating pH of a buffer
2 Illustration of buffering effect: Sodium acetate/acetic acid
3 Applications
4 Common buffer compounds used in biology
5 Making buffer solutions
5.1 Citric acid-phosphate buffer
6 See also
7 External links
8 Suppliers



[edit] Calculating pH of a buffer
The equilibrium above has the following acid dissociation constant:


Simple manipulation with logarithms gives the Henderson-Hasselbalch equation, which describe pH in terms of pKa:


In this equation

[A-] is the concentration of the conjugate base. This may be considered as coming completely from the salt, since the acid supplies relatively few anions compared to the salt.
[HA] is the concentration of the acid. This may be considered as coming completely from the acid, since the salt supplies relatively few complete acid molecules (A - may extract H + from water to become HA) compared to the added acid.
Maximum buffering capacity is found when pH = pKa, and buffer range is considered to be at a pH = pKa ± 1.


[edit] Illustration of buffering effect: Sodium acetate/acetic acid
The acid dissociation constant for acetic acid-sodium acetate is given by the equation:


Since this equilibrium only involves a weak acid and base, it can be assumed that ionization of the acetic acid and hydrolysis of the acetate ions are negligible. In a buffer consisting of equal amounts of acetic acid and sodium acetate, the equilibrium equation simplifies to

Ka = [H + ],
and the pH of the buffer as is equal to the pKa.

To determine the effect of addition of a strong acid such as HCl, the following mathematics would provide the new pH. Since HCl is a strong acid, it is completely ionized in solution. This increases the concentration of H+ in solution, which then neutralizes the acetate by the following equation.


The consumed hydrogen ions change the effective number of moles of acetic acid and acetate ions:



After accounting for volume change to determine concentrations, the new pH could be calculated from the Henderson-Hasselbalch equation. Any neutralization will result in a small change in pH, since it is on a logarithmic scale.


[edit] Applications
Their resistance to changes in pH makes buffer solutions very useful for chemical manufacturing and essential for many biochemical processes. The ideal buffer for a particular pH has a pKa equal to the pH desired, since a solution of this buffer would contain equal amounts of acid and base and be in the middle of the range of buffering capacity.

Buffer solutions are necessary to keep the right pH for enzymes in many organisms to work. Many enzymes work only under very precise conditions; if the pH strays too far out of the margin, the enzymes slow or stop working and can denature, thus permanently disabling its catalytic activity. A buffer of carbonic acid (H2CO3) and bicarbonate (HCO3-) is present in blood plasma, to maintain a pH between 7.35 and 7.45.

Industrially, buffer solutions are used in fermentation processes and in setting the correct conditions for dyes used in colouring fabrics. They are also used in chemical analysis and calibration of pH meters.