Module 1 - Proteins Enzymes

Question 1

What is an enzyme?

Answer 1

A biological catalysts that speeds up chemical reactions without being used up itself.

Question 2

How do enzymes affect the activation energy of molecules?

Answer 2

Enzymes lower the activation energy. More substrate molecules have enough activation energy to catalyse reactions.

Question 3

Describe the active site of an enzyme

Answer 3

Has a specific shape to each enzyme. Substrates with a complementary shape to the enzyme can bind to the substrate forming a enzyme-substrate complex.

Question 4

What is the shape of the active site determined by?

Answer 4

The tertiary structure of the enzyme of the polypeptide

Question 5

What is the lock and key theory?

Answer 5

This when the active site of an enzyme is rigid and inflexible meaning the enzyme and substrate can fit together perfectly.

Question 6

What is the induced fit model?

Answer 6

As the enzyme and substrate come together, the active site is more flexible therefore the active sites structure can change to fit the substrate. Enzyme-substrate complex can form.

Question 7

How is the specificity of an enzyme determined?

Answer 7

The active site of an enzyme is determined by the tertiary structure. This means that the amino acids that make up the sequence of the complex polypeptide chains determine the structure and function of the protein therefore only fitting a certain substrate.

Question 8

The effects of substrate concentration on an enzyme

Answer 8

The substrate concentration relates to the number of active sites that are colliding with substrates. At a low number of substrates, there is a low frequency collisions so rate of reaction is low. As we increase the amount of substrate molecules, rate of reaction increases as increase in frequency of collisions.

Question 9

What happens with substrate concentration after a vast amount of substrate molecules have been added?

Answer 9

This means all active sites have been filled with substrates so this is called Vmax (maximum rate of reaction). A graph will level off.

Question 10

The effects of enzyme concentration on an enzyme

Answer 10

If enzyme concentration is low but substrate concentration is high, this means that there will not be a lot of successful collisions happening over a period of time. Increasing enzyme concentration increases frequency of collisions.

Question 11

What are competitive inhibitors?

Answer 11

These are chemicals that can bind to the substrate for a short-period of time preventing substrates from binding to the enzyme. This means that they slow down the rate of reaction

Question 12

How can we decrease the chance of competitive inhibitors from attaching to the active site of an enzyme?

Answer 12

By increasing the substrate concentration meaning there is a higher chance that a substrate will bind to the active site and not the competitive inhibitor.

Question 13

What is an irreversible inhibitor and how is it harmful?

Answer 13

This is a competitive inhibitor that will remain attached to the active of the enzyme and cannot be removed no matter the concentration of the substrates.

Question 14

What is the structure of competitive inhibitors?

Answer 14

These are similar in shape to the substrates and block asses of the formation of ES complexes

Question 15

What is the structure of non-competitive inhibitors?

Answer 15

Non competitive inhibitors do not have a similar shape to the substrate because they do not bind to the active site?

Question 16

What do non-competitive inhibitors do to the shape of the active site of an enzyme

Answer 16

Non-competitive inhibitors do not bind to the active site and instead, they bind to another part of the actual enzyme called the allosteric site. This means that they impact the shape of the tertiary structure of the enzyme and therefore change the shape of the active site.

Question 17

How does the shape of the active site affect how substrate molecules bind to the active site?

Answer 17

As non-competitive inhibitors affect the shape of the active site by impacting the shape of the tertiary structure, this means that substrates are no longer complementary to the active site therefore can no longer bind to the active site making the enzyme denatured.

Question 18

The effect of temperatures on enzyme controlled reactions

Answer 18

As temperatures is increases, rate of reaction increases because of the increase in kinetic energy of the substrate and enzyme.

Question 19

What happens at high temperatures that causes the enzyme to denature?

Answer 19

At high temps, vibrations are more rapid causing bonds to break. The tertiary structure of the enzyme will being to change meaning the active site is no longer complementary to the substrate molecule.

Question 20

The effect of pH on enzymes

Answer 20

The active site forms temporary bonds to the substrate. pH can affect R groups from bonding to substrate therefore reducing the effectiveness of the bonding between active sites and substrates reducing the rate of reaction.

Question 21

How do we calculate the pH of a solution from the concentration of hydrogen ions?

Answer 21

pH = -log(h+)

1) Press log
2) Enter number of the concentration of hydrogen ions
3) Reverse the sign by flipping the negative sign.

Question 22

What is an example of a competitive inhhibitor?

Answer 22

Malonic acid competes with succinate for the active sites of succinic dehydrogenase, an important enzyme in the Krebs cycle of respiration.

Question 23

Why is insulin better taken as injection than as a pill?

Answer 23

If ingested then protease enzyme will break it down. If some escaped digestion then this means that it is likely to become denatured by low pH in the stomach. If it survives this then it would not be small enough to be small enough to be absorbed by small intestine then into bloodstream therefore would not reach body tissue