pH & Buffers

What are you measuring when you take the pH of a solution?

the number of hydrogen ions in a solution

What is the pH of an acid, base, or neutral solution?

acid >7, base

What is the concentration of ions in an acid?

contains more H+ ions and less OH- ions

What is the concentration of ions in a base?

contains less H+ ions and more OH- ions

What is the concentration of ions in a neutral solution?

the H+ ions and OH- ions are equal concentrations

How could we increase or decrease the pH of a solution with a pH of 9.5?

increase - add a base;
decrease - add an acid

What are buffers?

composed of weak acids (HA) and its conjugate base (A-)

How do buffers work?

resist pH changes by interacting with H+ or OH- ions that may be released or added in the solution

How do changes in pH protein activity?

changes in pH can add or subtract charged ions from a protein - changing shape and function

How are buffers used in biotech labs?

ensures that molecules will not be affected by small changes in H+ or OH- concentration during reactions or storage

What is the isoelectric point or pi?

represents the pH where the protein's positive
and negative charges are equal and the protein is
electrically neutral

What happens when the pi = pH?

the protein will precipitate out
of solution

What does the pKa indicate?

the pH at which a molecule is 50/50 ionized

What range of pH should a buffer be in relation to pi?

1 or 2 pH units away from pi

What solvent is added when making a buffer?

deionized water

A protein has a pH of 7.5. A buffer for this protein might be around a pH of 9.5. Which buffer would be best for this protein? - Use the chart in your notes.

borate

How should buffers be stored?

at room temperature or 4 C for several weeks

What procedures can be done to ensure that buffers stay uncontaminated?

filter and autoclave