BI.2.1.22 Enzymes at work - pH effects

Why do enzymes usually work only within very narrow pH ranges?

Even a small change in pH results in a significant change in hydrogen ion concentration. This has an effect on the enzyme tertiary structure and so the active site shape

A hydrogen ion carries a __________________ charge, so it will be attracted towards ___________________ charged ions, molecules or parts of molecules. As like charges repel, hydrogen ions will be repelled by ________________ charged ions, molecules or parts of molecules.

A hydrogen ion carries a positive charge, so it will be attracted towards negatively charged ions, molecules or parts of molecules. As like charges repel, hydrogen ions will be repelled by positively charged ions, molecules or parts of molecules.

All enzymes have their own optimum pH. This is the pH at which the ____ __ ________________ is highest. For many enzymes this optimum __ is around neutral

All enzymes have their own optimum pH. This is the pH at which the rate of reaction is highest. For many enzymes this optimum pH is around neutral

Tertiary structure bonds and interference with hydrogen ions

As hydrogen ions are increased in concentration, the positive charges are attracted to the negative chafes on the alpha helix and so replace the hydrogen bonds

At the optimum pH, the concentration of hydrogen ions in solution gives the _______________ structure of the enzyme the best overall shape. This shape holds the _______ _____ in the shape that best fits the ____________

At the optimum pH, the concentration of hydrogen ions in solution gives the tertiary structure of the enzyme the best overall shape. This shape holds the active site in the shape that best fits the substrate

Because of their charge, hydrogen ions can interfere with ____________ bonds and ____________ bonds holding the _________________ structure in place. This means that increasing or decreasing the concentration of hydrogen ions around an enzyme can alter the _________________ structure of the enzyme molecule. Changes in pH can cause changes to the shape of the ______ ______, and so change the rate of an enzyme-controlled reaction

Because of their charge, hydrogen ions can interfere with hydrogen bonds and ionic bonds holding the tertiary structure in place. This means that increasing or decreasing the concentration of hydrogen ions around an enzyme can alter the tertiary structure of the enzyme molecule. Changes in pH can cause changes to the shape of the active site, and so change the rate of an enzyme-controlled reaction

Explain why both increasing and decreasing pH away from the optimum results in a reduction in the reaction rate

Changing pH means changed to the hydrogen ion concentration. Since the tertiary structure of a protein is held in part by bonds derived from charge differences then changes to the hydrogen ion concentration will affect tertiary structure and so active site shape

Enzymes usually work in a fairly narrow __ range. Changes to pH altering the concentration of ___________ ____ even slightly, result in a fall in the r__________ _____ because the shape of the enzyme molecule is disrupted and so the shape of the active site is changed.

Enzymes usually work in a fairly narrow pH range. Changes to pH altering the concentration of hydrogen ions even slightly, result in a fall in the reaction rate because the shape of the enzyme molecule is disrupted and so the shape of the active site is changed.

Large numbers of hydrogen bonds and ionic bonds are responsible for holding the _______________ structure of an enzyme protein in place. This ensures that the ________ _______ of the enzyme is held in the right shape. These bonds are due to the ____________________ between oppositely charged groups on the ______ acids that make up the enzyme protein

Large numbers of hydrogen bonds and ionic bonds are responsible for holding the tertiary structure of an enzyme protein in place. This ensures that the active site of the enzyme is held in the right shape. These bonds are due to the attraction between oppositely charged groups on the amino acids that make up the enzyme protein

Measuring the effect of pH on enzyme action usually involves carrying out enzyme controlled reactions at different pH values using buffer solutions. The production of a ___________, or the disappearance of a _________________ can be measured in a variety of ways

Measuring the effect of pH on enzyme action usually involves carrying out enzyme controlled reactions at different pH values using buffer solutions. The production of a product, or the disappearance of a substrate can be measured in a variety of ways

The higher the concentration of hydrogen ions the _______ the pH value. This means that in solution acids contain a ____ concentration of hydrogen ions. In chemical terms, an acid is defined as a proton donor because hydrogen ions are also knows as __________.

The higher the concentration of hydrogen ions the lower the pH value. This means that in solution acids contain a high concentration of hydrogen ions. In chemical terms, an acid is defined as a proton donor because hydrogen ions are also knows as protons.

The _______________ ___ hypothesis states that an important part of catalyst in the active site relies on charged groups on the _-groups of the ______ acids that make up the active site. Increasing the concentration of hydrogen ions will alter the charges around the active site, as more hydrogen ions are attracted towards any negatively charged groups in the _______ ____

The induced fit hypothesis states that an important part of catalyst in the active site relies on charged groups on the R-groups of the amino acids that make up the active site. Increasing the concentration of hydrogen ions will alter the charges around the active site, as more hydrogen ions are attracted towards any negatively charged groups in the active site

Explain the the optimum pH for pepsin is different from the optimum pH for typsin even though both enzymes are proteases

The tertiary structure of each enzyme is held in place by a number of charge-based bonds. In each case, the optimum tertiary structure is achieved with the hydrogen ion concentration.

Individual hydrogen bonds are fairly weak Explain how such weak bonds can be responsible for holding the tertiary structure of of an enzyme molecule in place

There are many hydrogen bonds; each one is weak, but lots of them together are very stabilising

pH is a measure of the____________________ ion concentration with values for pH ranging from _ to __. In this range pH7 is ____________, below pH 7 is referred to as ____, above pH 7 is ____________

pH is a measure of the hydrogen ion concentration with values for pH ranging from 1 to 14. In this range pH7 is neutral, below pH 7 is referred to as acid, above pH 7 is alkaline