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Question 1

What is a catalyst?

Answer 1

A catalyst is a substance that increases rate of chemical reactions without being used in the reaction. They reduce the energy needed to start reactions making them more effective. Enzymes are an example of a catalyst.

Question 2

What is metabolism?

Answer 2

Metabolism= all chemical reactions the body is doing. This includes catabolism and anabolism.

Question 3

What is an active site?

Answer 3

An active site is a groove within the enzyme that binds to the substrate. Formed by specific tertiary folds of the protein which creates a unique shape and exposes r-groups that are chemically compatible with the substrate.

Question 4

What is a substrate?

Answer 4

The substrate is the reactant in an enzyme catalysed reaction. The substrate are the initial chemicals that bind to the active site and are transformed into the product. The substrate needs to be chemically compatible with the enzyme.

Question 5

Explain the induced fit model

Answer 5

The induced fit model states that while the substrate and enzyme need to be chemically compatible, they don’t have to be an exact fit. When close to each other, the attraction initiates binding and both the enzyme and substrate can adjust shape to facilitate bonding.

Question 6

What is activation energy?

Answer 6

Activation energy is the energy required to get the substrate into a transition state by breaking existing bonds as substrates are normally in stable, non-reactive states.

Question 7

What is an enzyme-substrate complex?

Answer 7

An enzyme-substrate complex is what is formed when the substrate is bound to the enzyme’s active site. The enzyme-substrate complex must form for the bonds in the substrate to break and the reaction to progress.

Question 8

What is the concept of enzyme-substrate specificity?

Answer 8

The concept that every enzyme acts on one or a group of similar substrates that are chemically compatible with the enzyme. Some can only catalyse 1 substrate while others can do a few similar ones. This increases efficiency and allows individual reactions to be regulated.

Question 9

What makes an enzyme unique from other catalysts?

Answer 9

Enzymes are catalysts within living organisms. They are always made of proteins.

Question 10

What is the difference between reactants and products?

Answer 10

Reactants= the initial substrates that come into a chemical reaction (substrates)
Products: the new substances that result from a chemical reaction

Question 11

What is an anabolic reaction?

Answer 11

Anabolic reactions build smaller molecules into bigger ones. 2+ substrates become** one** product.

Question 12

What is a catabolic reaction?

Answer 12

Catabolic reactions break larger molecules into smaller ones. One substrate becomes 2+ products.

Question 13

How does the shape of globular proteins make them ideal as enzymes?

Answer 13

Globular proteins have folded complex spherical shapes, which allows for folding to create specific grooves that expose r-groups that are chemically attracted to the substrate.

Question 14

What is the lock and key model?

Answer 14

The lock and key model was the previous method used to explain the enzyme substrate relationship. It thought that the enzyme and substrate need to have an exact shape match to be compatible.

Question 15

How do enzymes impact activation energy?

Answer 15

Enzymes speed up reactions by lowering the activation energy required. The enzyme aids in breaking the bonds so the energy needed for the reaction to progress lowers. Lower activation enercy means that reactions can occur more quickly and spontaneously in the body.

Question 16

What is an exergonic reaction?

Answer 16

Exergonic reactions release energy stored in the reactants

Question 17

What is an endergonic reaction?

Answer 17

Endergonic reactions consume energy to produce higher energy products.

Question 18

Draw the curve of an endergonic reaction with and without enzyme

Question 19

Draw the curve of an exogonic reaction with and without enzyme

Question 20

Explain the concept of collision theory

Answer 20

For an enzyme-substrate complex to form, the substrate and enzyme must collide with the correct orientation for them to be chemically aligned to bond. If there are more successful collisions, the rate of reaction will increase.

Question 21

What is denaturation?

Answer 21

When weak bonds break in extreme environments, this temporarily changes the shape and therefore the function. It can alter the very specific shape of the active site which can make it incompatible with the substrate.

Question 22

What role does molecular motion play in enzyme activity?

Answer 22

Motion provides the opportunity for a substrate to collide into an enzyme. However, sometimes when both enztmes and substrates are moving rapidly, the orientation becomes misaligned- must strike a balance!

Question 23

How can enzymes and substrates be immobilised to increase activity?

Answer 23

Usually substrates move freely within aqueous solutions and the enzyme can be moving or anchored to a cell membrane or immobilised through other strategies. This can work by having a well-placed stationary active site that substrates can collide into. There are also some instances where the substrate is immobilised instead.

Question 24

How does temperature impact the effectiveness of enzymes?

Answer 24

Molecules move more rapidly at higher temperatures due to an increase in kinetic energy. This means enzymes have more successful collisions, causing an increase in reaction rate. However, at high temperatures enzymes can denature, decreasing enzyme function.

Question 25

How does pH impact the effectiveness of enzymes?

Answer 25

The shape of the active site is determined by the placement of charged amino acids. At lower pH’s, extra H ions can bond to the enzyme and reduce compatibility with substrates. At higher pH’s, the same thing can happen with OH groups. However, some enzymes are adapted to more acidic or alkaline environments.

Question 26

How does the substrate concentration impact the rate of reaction?

Answer 26

At lower concentrations of substrate, enzymes are not working effectively as not all active sites are filled. As substrate concentration increases more active sites become filled and the reaction rate increases. Once every enzyme is filled with substrate, the reaction reaches its peak and plateaus.

Question 27

How can the rate of enzyme catalysed reaction be measured?

Answer 27

dissapearence of reactant/ substrate divided by change in time
OR
appearence of product divided by change in time

Question 28

Draw the graph of the effect of temperature on enzymes

Question 29

Draw the graph of the effect of pH on enzymes

Question 30

Draw the graph of the effect of substrate concentration on enzymes

Question 31

What is a multienzyme complex?

Answer 31

Many metabolic reactions require multiple enzymes to act on different intermediates to create the final product. When multiple enzymes are located close together to work on one metabolic pathway, it is called a multienzyme complex.

Question 32

What is an inhibitor?

Answer 32

An inhibitor is a molecule that temporarily binds to an enzyme, halting its activity. This can be intentional to regulate enzymes so they are only active when required, or can be a consequence of toxins. Inhibitors are always reversible.

Question 33

What is an allosteric site?

Answer 33

An allosteric site is the second key site some enzymes have in addition to the active site. This site can be used to inactivate the enzyme through bonding to it. It can often be used to regulate the enzyme. Some enzymes also use it to initiate/ amplify enzyme activity.

Question 34

What is feedback inhibition?

Answer 34

Feedback inhibition is the process of preventing enzyme action by using the product as its inhibitor. This means that when the concentration of the product increases it can inhibit the enzyme. It often inhibits the first enzyme in a metabolic pathway so intermediates aren’t produced. Is an example of a negative feedback loop.

Question 35

Explain the difference between an intracellular and extracellular enzyme-catalysed reaction

Answer 35

Intracellular reactions involve enzymes working inside cells e.g enzymes involved in cell respiration in mitochondria
Extracellular reactions involve enzymes being secreted outside the cell to work e.g digestive enzymes being released into intestines

Question 36

How is heat loss from metabolic reactions useful for endotherms?

Answer 36

Endotherms use metabolic reactions to create and maintain body warmth. In cold environments, metabolic rate can increase to create heat through actions like shivering.

Question 37

Explain a linear metabolic pathway

Answer 37

Linear metabolic pathways progress in a line from reactant to product through intermediates- no recycling of reactants or intermediates
Example:
Reactant– Intermediate 1— Intermediate 2— PRODUCT

Question 38

Explain a cyclical metabolic pathway

Answer 38

Cyclical pathways involve some reactants being recycled during the reaction
Example
Reactant— Intermediate 1— Inrtermediate 2— PRODUCT and Reactant

Question 39

What is competitive inhibition?

Answer 39

Competitive inhibitors are inhibitors that bind to the active site and block substrate. It is temporary. An increase in substrate concentration can limit impact as it increases the chance of the substrate bonding rather than the inhibitor.

Question 40

What is non-competitive inhibition?

Answer 40

Non-competitive inhibitors are inhibitors that bind to the allosteric site, changing enzyme shape and making it ineffective. It is temporary. Changing substrate concentration has no effect.

Question 41

How do statins act as inhibitors?

Answer 41

Statins are a type of medication that reduces high cholesterol by acting as a competitive inhibitor. It binds to the active site of enzyme HMG-CoA reductase that synthesises cholesterol. When bound to the enzyme, production of cholesterol decreases.

Question 42

Explain end-product inhibition in the isoleucine pathway

process and benefits

Answer 42

1. Threonine (amino acid)
   (enzyme 1)
2. Intermediate
   (enzyme 2)
3. Intermediate
   (enzyme 3)
4. Intermediate
   (enzyme 4)
5. Intermediate
   (enzyme 5)
6. Isoleucine (product, amino acid)

• Isoleucine binds to the allosteric site if there is a build up and will be ripped off if there is not enough, allowing the enzyme to begin turning threonine into intermediate
• Example of non-competitive inhibition
  Benefits:
• By having the product block the first enzyme, unusable intermediates are not made, saving energy
• By using the product as the inhibitor, it will naturally regulate based on amount