BI.2.1.21 Enzymes and temperatures

An enzyme can catalyse a reaction only if a ______________ molecule collides with the active site of the enzymes so that an _________-substrate ___________ is formed. It is important to remember that the random movements of enzyme and substrate molecules lead to these collisions. If the kinetic energy of both enzyme and substrate molecules is increased by heating, there will be increased number of __________________ between enzymes and substrates. More collisions between enzyme and substrate means an increased _____ __ __________-, so more product will be formed

An enzyme can catalyse a reaction only if a substrate molecule collides with the active site of the enzymes so that an enzyme-substrate complex is formed. It is important to remember that the random movements of enzyme and substrate molecules lead to these collisions. If the kinetic energy of both enzyme and substrate molecules is increased by heating, there will be increased number of collisions between enzymes and substrates. More collisions between enzyme and substrate means an increased rate of reaction, so more product will be formed

Applying heat to molecules not only males them move faster, it also makes the molecules __________. These vibrations put strain on the bonds that hold the molecules together. In large molecules such as enzymes, the vibration of the molecules can break the weaker bonds such as_______________ bonds and ________ bonds. These weaker bonds occur in large numbers in an enzyme molecule and are responsible for holding the ___________________ structure in place. In particular, these bonds maintain the _______ ________ in its correct shape. As heat is increased, more and more bonds are broken. The tertiary structure is held less and less in the shape needed to keep the active site in its working form. This means the _____ ___ ____________________ will decrease. If enough of these bonds are broken, the whole _________ ____________________ will unravel and the enzyme will stop working. As with all proteins, if the tertiary structure of an enzyme if changed significantly it cannot ________________. This is not reversible, even if the temperature is lowered again, the tertiary structure is too damaged and the enzyme is ___________________

Applying heat to molecules not only males them move faster, it also makes the molecules vibrate. These vibrations put strain on the bonds that hold the molecules together. In large molecules such as enzymes, the vibration of the molecules can break the weaker bonds such as hydrogen bonds and ionic bonds. These weaker bonds occur in large numbers in an enzyme molveule and are responsible for holding the tertiary structure in place. In particular, these bonds maintain the active site in its correct shape. As heat is increased, more and more bonds are broken. The tertiary structure is held less and less in the shape needed to keep the active site in its working form. This means the rate of reaction will decrease. If enough of these bonds are broken, the whole tertiary structure will unravel and the enzyme will stop working. As with all proteins, if the tertiary structure of an enzyme if changed significantly it cannot function. This is not reversible, even if the temperature is lowered again, the tertiary structure is too damaged and the enzyme is denatured.

What types of bond would you expect to find in greater numbers holding the tertiary structure of heat-resistanct enzymes, compered with more hear-sensitive enzymes? Explain

Disulphide bonds. These are not broken by heat, only by reducing sugars

Suggest why the normal body temperature of mammals is slightly below the optimum temperature of most of the enzymes that occur in the organism

In exercising, heat is generated by the organism in the muscles which takes some time to remove, also some infections lead to fevers. If the normal body temperature was too near the optimum temperate for the enzymes, then in situations of increased temperature many enzymes may be denature. A higher body temperature would require more energy and might denature other proteins

In modern genetic engineering, heat-resistant enzymes are used to catalyse reactions involved in making many copies of DNA segments. The process is known as the ______________ ______ ___________ and is very similar to DNA replication

In modern genetic engineering, heat-resistant enzymes are used to catalyse reactions involved in making many copies of DNA segments. The process is known as the polymerase chain reaction and is very similar to DNA replication

Explain why increased kinetic energy increases the rate of reaction in an enzyme-controlled reaction

Increased kinetic energy leads to increased numbers of collisions between enzyme and substrate molecules and so increases rate of reaction

Increasing the temperature ____________________ the rate of reaction of an enzyme-controlled reaction at first, but as the temperature increases further, the rate of reaction______________. Eventually the enzyme will stop working.

Increasing the temperature increases the rate of reaction of an enzyme-controlled reaction at first, but as the temperature increases further, the rate of reaction decreases. Eventually the enzyme will stop working.

Many enzymes have an optimum temperature somewhere between __ and __°. But there are some organisms for which such enzymes would be useless. The temperatures at which these organisms live means they must have____-__________ ____________

Many enzymes have an optimum temperature somewhere between 40 and 50°. But there are some organisms for which such enzymes would be useless. The temperatures at which these organisms live means they must have heat-resistance enzymes.

The molecules in a gas or liquid move around continually. They have natural __________ energy and move continuously and randomly. These movements mean that molecules continually collide with each other. If a gas or liquid is heated, the kinetic energy of the molecules is _________________ and they move around more quickly. This makes molecules collide with each other more often. It also means that when they do collide, as they are moving at greater speed, they collide with greater forces

The molecules in a gas or liquid move around continually. They have natural kinetic energy and move continuously and randomly. These movements mean that molecules continually collide with each other. If a gas or liquid is heated, the kinetic energy of the molecules is increased and they move around more quickly. This makes molecules collide with each other more often. It also means that when they do collide, as they are moving at greater speed, they collide with greater forces

The temperature that gives the maximum rate of reaction is the enzymes __________________ temperature. It is a balance between increasing the __________________ of the enzyme molecule which breaks the bonds that hold the _______________ structure in place

The temperature that gives the maximum rate of reaction is the enzymes optimum temperature. It is a balance between increasing the vibration of the enzyme molecule which breaks the bonds that hold the tertiary structure in place