Yr 11 - SCB - B2.4 - Enzymes

Question 1

role of enzymes as biological catalyst

Answer 1

To speed up reactions within the organism

Question 2

structure of enzymes

Answer 2

They are the active site that the substrate fits In to

Question 3

define enzyme

Answer 3

globular proteins that are folded into complex, specific shapes that allow only one type of molecule to fit into it. They are biological catalyst as they speed up biochemical reactions without being used in the reaction

Question 4

difference between lock and key model and induced fit model

Answer 4

Lock and key: The substrate has a certain shape that allows the substrate to fit in, no others, to form a enzyme complex

Induced fit: Enzymes are flexible because of week hydrogen bonds so when a substrate binds it changes the shape of the active site aswel. Enzymes achieve specificly because only the substrate with the correct functional group can alter the configuration

Question 5

Factors that effect enzyme activity

Answer 5

temperature
pH
enzyme concentration
substrate concentration.
co-enzymes 
inhibitors

Question 6

Explain temp factor

Answer 6

If the temperature is too high the shape of the enzyme irreversibly changes - the active site which means the enzyme will no longer work.
When this happens the enzyme is denatured.

Enzymes and substrates have more kinetic energy as temp increases and therefore are moving faster so there are more successful collisions per second and more enzyme-substrate complexes form.

Question 7

Explain ph factor

Answer 7

If the pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes - the active site which means the enzyme will no longer work. When this happens the enzyme is denatured.

Changing the pH of a solution outside optimum means that the number of H+ ions and OH– ions present in the solution is changed. These interact with the amino acids in the enzyme/protein and change the bonding.

Question 8

Substrate and enzyme concentration

Answer 8

As substrate and enzymes increase so does rate of reaction to a point. As there is not an unlimited number of enzymes, eventually all are in use and are therefore saturated with substrates.

Question 9

What are co-enzymes

Answer 9

co-enzymes alter the shape of the active site in such a way that it can effectively combine with substrates.

Question 10

What are inhibitors

Answer 10

inhibitors decreases rate of reaction because inhibitors are poisons that alter or block the active site, preventing substrates from binding.

Question 11

Explain co-enzyme factor

Answer 11

Some enzymes require the addition of a non-protein substance called a cofactor before they can catalyze a reaction

• activators – inorganic groups that are permanently bound to the enzyme eg iron zinc copper
• coenzymes – organic molecules that bind only temporarily to the enzyme, transferring a chemical group eg vitamin c and ATP

Question 12

Explain inhibitors factors

Answer 12

Substances can interfere with enzyme activity are called inhibitors

• Competitive (active site directed) or non- competitive (non-active site directed). They might compete for the active sight which block the substrate eg poisons
• Reversible or irreversible, depending on whether their inhibitory effect on the enzyme is permanent or not.