Enzyme action

Question 1

Name the three conditions required for normal chemical reactions e.g sucrose + water (substrates) -> glucose and fructose (products)

Answer 1

• Substrates must collide with sufficient energy to alter the arrangement of their atoms to form products
• The free energy of the products must be less than that of the substrates
• Many reactions require an initial amount of energy to start. The min. amount of energy needed to activate the reaction in this way is called activation energy

Question 2

How do enzymes alter these conditions (conditions required for normal chemical reactions) and what does this do (explain in detail)

Answer 2

They lower the activation energy level so enzymes can allow reactions to happen at a lower temp. than normal - enables some metabolic processes to occur rapidly at human body temp. (relatively low for chem. reactions)

(Straining the bonds lowers the level of energy)

Question 3

What structure of proteins determines the functionality of the enzymes?

Answer 3

The tertiary structure - because of the further twisting of the secondary structure + can become complex specific shape to a specific protein which determines the behaviour of the protein

Question 4

What is the optimal temp. of enzymes and why is this their optimal temp.?

Answer 4

Most enzymes have an optimal temp. of 37 degrees
Too high - active site starts to change shape (substrate will no longer fit)
Too low - the enzymes won’t have enough energy to function

Question 5

Define activation energy

Answer 5

The movement of particles and the required energy for a reaction to happen

Question 6

Define intracellular and extracellular

Answer 6

Intracellular: inside the cell
Extracellular: outside the cell

Question 7

What is the substrate and what does it form when it binds to the enzyme?

Answer 7

The substrate the molecule in which the enzyme acts on. It fits exactly onto the active site and forms an enzyme-substrate complex.
The substrate is held within the active site by bonds that temporarily form between certain amino acids of the active site and groups on the substrate molecule

Question 8

What can the active site also be known as?

Answer 8

A small ‘depression’ within the enzyme

Question 9

What does the induced fit model state has to happen in order for a reaction to take place?

Answer 9

• The active site of the enzyme only takes the shape of the substrate when they collide
• The flexibility of the polypeptide chain allows enzyme to shape its active site around the substrate if all the right bonds can be formed in all the right places
• If this happens the reaction can take place

Question 10

Describe the induced fit model when the reaction takes place

Answer 10

• The enzyme holds the substrate molecules close enough to overcome repulsion between molecules
• While breaking a substrate down, the enzyme puts strain on the substrate, reducing the energy needed to break the molecule (the strain distorts particular bond/s in the substrate and lowers the activation energy)
  (The enzyme wants to go back to its usual shape so it breaks down the substrate)
• The enzyme releases the substrate which has been broken down and the enzyme returns to original shape

Question 11

Describe the lock and key model

Answer 11

It states that the active site (lock) is specific to the substrate (key) + the active site will only break down the substrate if it is the specific shape.
If the substrate has been altered, it will not fit the active site.