Summary
The pH scale measures hydrogen ion concentration; buffers resist pH change to keep conditions stable in cells.
In depth
pH is the negative log of hydrogen ion concentration, so each unit is a tenfold change. Cells operate near pH 7.2 to 7.4, and blood is kept at 7.35 to 7.45. Enzyme shape depends on pH, so small shifts alter activity.
Buffers contain a weak acid and its conjugate base that absorb added H+ or OH-. In blood the bicarbonate system (CO2 plus water, carbonic acid, bicarbonate) is the main buffer.
The bicarbonate system is the main blood buffer: CO2 plus water is in equilibrium with carbonic acid and then bicarbonate plus H+, so the lungs and kidneys can adjust pH by removing CO2 or bicarbonate. Proteins, including haemoglobin, and phosphate act as additional buffers in cells.
Acidosis (pH below 7.35) and alkalosis (above 7.45) disturb enzyme and ion function; uncontrolled diabetes causes ketoacidosis, while hyperventilation causes respiratory alkalosis. Each pH unit change is tenfold in H+, so a drop from 7.4 to 7.0 means 2.5 times more H+.
Example: soil pH determines which plants thrive; hydrangea flower colour changes from pink to blue as soil becomes more acidic and aluminium becomes available.
Frequently asked questions
What is pH and Buffers?
The pH scale measures hydrogen ion concentration; buffers resist pH change to keep conditions stable in cells.
Which area of biology covers pH and Buffers, and how advanced is it?
pH and Buffers is one of the 51 topics in Biomolecules & Biochemistry. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Allosteric Regulation, Free Energy in Biology, Denaturation.
Can you give an example of pH and Buffers?
During hard exercise, lactic acid is buffered to avoid a sharp pH drop.
What should I learn before pH and Buffers?
pH and Buffers is a Beginner topic, so no earlier topic is required. Other Beginner topics in Biomolecules & Biochemistry that pair well with it include Water Properties, Carbon Chemistry, Carbohydrates.
What topics are related to pH and Buffers?
The closest topics to pH and Buffers are Allosteric Regulation, Free Energy in Biology, Denaturation, Amino Acids. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand pH and Buffers?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for pH and Buffers. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is pH and Buffers different from Allosteric Regulation?
pH and Buffers: The pH scale measures hydrogen ion concentration; buffers resist pH change to keep conditions stable in cells. Allosteric Regulation: Binding of a molecule at a site other than the active site changes enzyme shape and activity. Read both side by side and note what each one explains.
How should I study pH and Buffers step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Allosteric Regulation and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.