C1.1

Question 1

Structure and Function of Enzymes

What is a Catalyst

Answer 1

A substance that increases the rate of chemical reactions without being used up in the reaction.
- Catalysts reduce the energy needed to start reactions –> enable them to get started more quickly, progressing more effectively.
- Enzymes are a special type of catalyst.

Question 2

Structure and Function of Enzymes

What is Metabolism?

Answer 2

The set of interacting and independent chemical reactions that occur in the body.
- include reactions that break down larger molecules into smaller building blocks (CATABOLISM) and reactions that assemble those building blocks into important larger substances needed for the body (ANABOLISM)

Question 3

Structure and Function of Enzymes

What is an Active Site?

Answer 3

WITHIN the enzyme, there is a groove that is the binding site for SUBSTRATES.
- Active site is formed by the specific tertiary folds of the protein to create a very unique shape that has EXPOSED R-GROUPS that are chemically compatible to the substrate.

Question 4

Structure and Function of Enzymes

What is a Substrate?

Answer 4

The reactant (s) in an enzyme catalysed reaction.
- the initial chemical (s) that bind to the active site and are transformed into a product.
- it needs to be chemically compatible/ the correct shape for it to bind to an enzyme.

Question 5

Structure and Function of Enzymes

What is the Induced-Fit Model?

Answer 5

• While substrate and active site need to be chemically compatible, they do not have to be a close exact fit.
• When they are near each other, the attraction initiates binding but both the enzymes and the substrate can make adjustments to their shape to ease bonding.

Question 6

Structure and Function of Enzymes

What is Activation Energy

Answer 6

Substrates need to become reactive/enter a transition state to become products.
- Normally stable/ non-reactive –> the existing bonds between them need to be broken.
- ENERGY is required to get them to recieve energy, this energy is called the activation energy.
- It is the energy needed to get reactants into a transition state by breaking existing bonds.

Question 7

Structure and Function of Enzymes

What is an Enzyme-Substrate Complex

Answer 7

• During when the substrate is bound to the enzyme’s active site, that state is called the enzyme-substrate complex.
• This complex HAS TO FORM FOR THE BONDS IN THE SUBSTRATE TO BE BROKEN and for the reaction to progress.

Question 8

Structure and Function of Enzymes

What is Enzyme-Substrate Specificity?

Answer 8

Every enzyme acts on one or a group of specific substrates that are chemically compatible to the substrate of that enzyme.
- Only some enzymes can catalyse one specific substrate while other may be able to act of a couple of similar ones.
- The specificity increases efficiency and allows for reactions to be regulated.

Question 9

Structure and Function of Enzymes

Enzymes as a unique catalysts

Answer 9

• Enzymes are a unique catalyst becomes it is inside a living organism.
• Enzymes are ALWAYS made up on PROTEINS.

Question 10

Structure and Function of Enzymes

Reactant vs Products

Answer 10

Reactants:
- The initial substances that come into a chemical reaction are called the reactants.

Products: The new substances that form as a result of the chemical reaction are called products.

Question 11

Structure and Function of Enzymes

Anabolic vs Catabolic Reactions

Answer 11

Anabolic: build smaller molecules into larger ones

Canabolic: reactions that break larger molecules into smaller ones.

IN THE CONTEXT OF ENZYMES:
- Two or more substrates become one product in an annobolic reaction.
- One substrate becomes two or more products.

Question 12

Structure and Function of Enzymes

Globular Proteins Ideal for Enzymes

Answer 12

Globular proteins make ideal enzymes because of their folded complex spherical shapes.
- allos for folding to create specific grooves that have R groups exposed that are chemically attracted to the substrate.

Question 13

Structure and Function of Enzymes

Induced Fit vs Lock and Key Model

Answer 13

Induced Fit Model:
- More accurate
- Shape needs to be generally compatible but both the enzyme and substrate can shift/ alter shape a little to facilitate a tighter bonding.

Lock and Key Mode
- Needed to have an exact shape match between enzymes and substrates

Question 14

Structure and Function of Enzymes

Enzymes lower Activation Energy

Answer 14

Enzymes speed up reactions by lowering the activation energy.
- Activation energy: energy needed to make the substrates reactive by breaking existing bonds.
- Enzyme aids in breaking the bonds so the amount of energy needed for the reaction to progress LOWERS.
- With less energy needed, creaction occur more frequently and randomly.

Question 15

Structure and Function of Enzymes

Endergonic vs Exogonic Reactions

Answer 15

Exergonic: release energy stored in the reactants.

Endergonic: Consume energy to produce higher energy products.

(Enzymes are helpful in both reaction types)

Question 16

Factors impacting Enzyme Reactions

What is Collision Theory?

Answer 16

• For an enzyme-substrate complex to form, the substrate and enzyme must collide (IN THE CORRECT ORIENTATION for the substrate to land in the actice site to be chemically alinged.
• More succesful collisions between substrate and active site increases the rate of a reaction.

Question 17

Factors impacting Enzyme Reactions

What is Denaturation

Answer 17

• In extreme environments, the weak bonds in a protein are broken, which makes them temporarily change shape which impacts its function.
• When the protein is an enzyme, the broken bonds and shape change alter the very specific shape of the ACTIVE SITE and render it no longer compatible to the substrate.

Question 18

Factors impacting Enzyme Reactions

The role of Molecular Motion for Enzymes

Answer 18

Molecules are always in motion.
- Motion gives the opportunity for a substrate to collide into an enzyme.
- Temperature increases motion, thus enzyme activity.
- When however both enzymes and substrates move, the orientation ends up unalinged.

Question 19

Factors impacting Enzyme Reactions

Immoblilisation of Enzymes and Substrates

Answer 19

• Substrates normally move freely in aqueous solution.
• Enzyme may also be moving, but can be immobilised by anchoring to a cell membrane possibly.
• Here, active site is stationary: easier to collide into.
• Can work vice versa.

Question 20

Factors impacting Enzyme Reactions

Impact of Temperature on Enzymes

Answer 20

• Molecules move faster at higher temps due to an increase of kinetic energy.
• When temp increases, enzymes have more succesful collisions leading to an icnreased reaction rate.
• HOWEVER, at very high temps, weaker bonds in the TERTIARY STRUCTURE can break and the enzyme denatures, which essentially stops enzyme function.

Question 21

Factors impacting Enzyme Reactions

Impact of pH on Enzymes

Answer 21

The shape of the ACTIVE SITE of the enzyme depends on the placement of charged amino acids.
- At low pH values (HIGHLY ACIDIC), extra H+ ions can bond to the enzymes and reduce its compatibility with substrates (or bind to them.)

• Similarly in alkaline environments, -OH groups can do the same.
• Some enzymes specifically adapted for more acidic or alkaline environments so the pH of each enzyme varies.

Question 22

Factors impacting Enzyme Reactions

Impact of substrate concentration on enzymes

Answer 22

• When concentration of substrate is low, enzymes are not working effectively as they can.
• Increase the concentration of substrates, more active sites become filled, which increases the reaction rate.
• EVENTUALLY, everyh enzyme will be filled with a substrate and the reaction rate reaches its maximum rate and pleatues.
• Adding more substrate after that has no effect.

Question 23

Factors impacting Enzyme Reactions

Measuring enzyme rate of reaction

Answer 23

Two ways of monitoring the progression of a reaction –>
1.) monitoring the disappearance of a reactant/ substance
OR
2.) by appearance or accumulation of the product.
- Calculate the rate = change in product/ reaction over the change in time.

Question 24

Enzyme Inhibition

What are multienzyme complexes?

Answer 24

• Lots of metabolic reactions –> require MANY ENZYMES that act on different intermediates to create the final product.
• When multiple enzymes are located close to one another to work on one metabolic pathway –> multienzyme complex.

Question 25

Enzyme Inhibition

What is an inhibitor?

Answer 25

A molecule that temporarily binds to an enzyme, halting its activity while it is bound.
- Can often be used intentionally in living organisims to regulate enzymes and ensure they are active ONLY WHEN NEEDED.
- Other times, inhibitors can be unattended consequences of toxins.
- Inhibitors are almost always reversible.

Question 26

Enzyme Inhibition

What is an allosteric site?

Answer 26

Many enzymes have a second key site in addition to the active site.
- Used for regulation or to activate/ inactivate the enzyme.
- Second site is used by inhibitors to bind to inactive the enzyme, however some enzymes use it to initiate or amplify enzyme activity.

Question 27

Enzyme Inhibition

What is Feedback Inhibition?

Answer 27

Inhibitors can regulate enzymes to prevent them front working unnecessarily.
- To do so, the product can act as an inhibitor; when the concentration of the product increases it can inhibit the enzyme.
- Usually will inhibit the FIRST ENZYME IN A METABOLIC PATHWAY, which is often called end-product inhibition.

Question 28

Enzyme Inhibition

Intracellular vs Extracellular Reactions

Answer 28

• Some enzymes work inside cells and they are INTRACELLULAR ENZYME REACTIONS ( enzymes involved in cellular respiration inside the mitochondria )
• Other enzymes work in extracellular environments ( digestive enzymes released into the intestines break down food. )

Question 29

Enzyme Inhibition

Metabolic Heat Loss for Endotherms

Answer 29

Metabolic reactions (cellular respiration included) create heat loss, which is then released into the body.
- Endotherms that strive to maintain a consistent internal temperature use this to help maintain body warmth.
- When they are in colder environments, metabolic rate increases in order to create that heat –> which can be done by increasing muscle activity (SHIVERING)

Question 30

Enzyme Inhibition

Linear vs Cyclical Metabolic Pathways

Answer 30

Metabolism often involves enzymes.
- earlier enzymes create intermediates that the next enzymes work on.
LINEAR: there is no recycling of REACTANTS.
CYCLICAL: some reactants are often recycled during the reactions.
- Cellular respiration involves a linear pathway (GLYCOLYSIS) and a cyclical pathway (KREBS CYCLE.)

Question 31

Enzyme Inhibition

Competitive vs Non-Competitive Inhibition

Answer 31

TWO GENERAL CATAGORIES OF INHIBITORS.
1.) Competitive: bind to the active site and BLOCK the substrate from binding.
- Increasing the substrate concentration can limit the impact since it increases the chances of a substrate instead of inhibitor on landing in active site.

2.) Non-Competitive: inhibitor binds to the allosteric site, CHANGING the overall enzyme shape –> ineffective.
- Substrate concentration has no impact.

Question 32

Enzyme Inhibition

Statins as Inhibitors

Answer 32

Statins are a medication that reduce high cholestral by acting as a COMPETITIVE INHIBITOR.
- Binds to the active site of the enzyme HMG-CoA reductase that synthesises cholesterol.
- When statin is bound to the enzyme –> production of cholesterol decreases.