Enzymes/Metabolism

Question 1

What are biochemical processes?

Answer 1

Chemical reactions that occur in all cell to produce products required by cells.

Question 2

What is metabolism?

Answer 2

The sum of all biochemical processes in a body.

Question 3

What do chemical reactions often occur in?

Answer 3

Series of steps.

Question 4

Why do chemical reactions occur in steps?

Answer 4

Because cells require a certain amount of energy to maintain the processes of generating products from reactants.

Question 5

What are the steps of a chemical reaction?

Answer 5

Initial reactants -> product A -> product A (using enzyme and cofactor) -> Final product (using enzyme)

Question 6

What allows the process of a chemical reaction to continue?

Answer 6

The final product being removed.

Question 7

How can the final product be removed?

Answer 7

It can be stered or expelled.

Question 8

What is an anabolic reaction?

Answer 8

The synthesis of simple molecules to form more complex ones (monomers into polymers).

Question 9

What do anabolic reaction require?

Answer 9

They usually require energy, this energy usually comes from catabolic reactions.

Question 10

What type of reaction is an anabolic reaction? Why?

Answer 10

Endergonic, because the energy of the reactants is less than that of the products.

Question 11

What is a catabolic reaction?

Answer 11

The breakdown of complex molecules into simpler ones (polymers into monomers).

Question 12

What do catabolic reactions release?

Answer 12

Usually release energy when the chemical bonds are breaking.

Question 13

What type of reaction is a catabolic reaction? Why?

Answer 13

Exergonic, because there is less energy in the products than there was in the reactants.

Question 14

Draw the cycle of catabolic, anabolic and energy reactions.

Answer 14

Check book for answer.

Question 15

What is the role of internal membranes?

Answer 15

Different organelles provide different environments for different chemical reactions to occur in. The internal plasma membrane of cells divide these organelles so they can maintain their own optimum environments and therefore contain their required enzymes.

Question 16

What is an enzyme?

Answer 16

A biological catalyst, usually a protein, that speeds up chemical reactions in cells by lowering the activation energy required.

Question 17

What are the two types of enzymes?

Answer 17

Intracellular and extracellular.

Question 18

What are intracellular enzymes?

Answer 18

Enzymes inside cells.

Question 19

What are extracellular enzymes?

Answer 19

Produced by cells but take effect outside the cells, e..g amylase in saliva.

Question 20

Are enzymes changed after reactions?

Answer 20

Enzymes remain unchanged and can be reusable but over time temperature/acidity can change their shape making them no longer complementary to their substrate.

Question 21

Can enzymes be used in all types of reactions?

Answer 21

Enzymes are only specific to ONE type of reaction.

Question 22

Why do we need enzymes?

Answer 22

• Without enzymes, the chemical reactions would occur too slowly to maintain life.
• Over 100 reactions take place in a single cell, enzymes allow organisation of these reactions by having specific functions in a particular place.

Question 23

What is activation energy?

Answer 23

The minimum amount of initial energy required to start a chemical reaction.

Question 24

How is activation energy supplied?

Answer 24

Usually supplied in the form of heat energy that reactants absorb from their surroundings.

Question 25

What do enzymes do to activation energy?

Answer 25

Enzymes lower the activation energy required for a reaction to take place by destabilising chemical bonds by weakening them.

Question 26

How does an enzyme bind to a substrate and how does an enzyme controlled reaction occur?

Answer 26

• Enzymes have different shapes that allow them to bind to specific reactants (substrates).
• When an enzyme controlled reaction occurs the enzyme and substrate molecule join for a short time to form an enzyme-substrate complex.
• Each enzyme has a precise location where the substrate can attach called the active site.

Question 27

What are the two models for enzymes?

Answer 27

• Lock and key model.
• Induced fit model.

Question 28

What is the lock and key model?

Answer 28

The original model, that the folding of the enzyme protein, forms a groove or pocket shaped active site that is highly specific for a particular substrate. The substrate must be of a complementary shape in order for binding to occur - like a lock and key.

Question 29

What is the induced fit model?

Answer 29

The more widely accepted model, in which the shape of the enzyme is not fixed. The bonds that form between the enzyme and its substrate are thought to slightly modify the shape of the enzyme so that the substrate can be accommodated.

Question 30

What do the enzymes in the induced fit model have?

Answer 30

They have broad specificity. Meaning, substrates still only bind to a few enzymes of a similar shape but there can be a conformational shape change in the active site.

Question 31

What happens to the bonds in the substrate in the induced fit model?

Answer 31

The bonds in the substrate molecule are stretched and bent during this interaction which lowers the activation energy required to start the reaction.

Question 32

What happens to the active site after the product is released in the induced fit model?

Answer 32

After the product is released the active site returns to its original shape.

Question 33

What is enzyme denaturing?

Answer 33

When an enzyme is exposed to heat/acidity not within its optimum range, the shape of the active site may change and its substrate will no longer bind with it.

Question 34

Why can enzymes denature?

Answer 34

Enzymes are sensitive to changes in temperature and pH and different enzymes have different optimum ranges of these factors.

Question 35

What happens to enzymes in their optimum temperature?

Answer 35

At the optimum temperature molecules are more active and collide more often which increases the opportunity for the substrate to collide with its enzyme.

Question 36

What happens to enzymes at temperatures lower than their optimum?

Answer 36

Lower temperatures means lower enzyme action which slows chemical reactions as less substrates are binding with their enzymes.

Question 37

What happens to enzymes at temperatures higher than their optimum?

Answer 37

As the temperature increases the amino acids that make up the protein move around more, causing the. hydrogen bonds between them to break, altering the shape of the active site (denaturing).

Question 38

What happens to enzymes in the human body if it overheats?

Answer 38

It can cause the enzymes in the brain to denature which can lead to seizures and eventually death as the chemical reactions are not occurring.

Question 39

What is the optimum temperature for most enzymes in the human body?

Answer 39

37ºC

Question 40

Do enzymes have the same optimum pH?

Answer 40

Some enzymes can work in a broad range of pH, others have a narrow pH range. Not all enzymes have the same optimum pH.

Question 41

What does an enzyme’s optimum pH depend on?

Answer 41

The sensitivity of an enzyme to pH depends on the enzyme’s environment, e.g. pepsin in the stomach must have a tolerance for a low pH (acidic) environment.

Question 42

What happens to an enzyme if not in its optimum pH range?

Answer 42

If the pH becomes too acidic/alkaline, the shape of the enzyme can change and it becomes denatured.

Question 43

What does increasing the substrate concentration do?

Answer 43

Increasing the concentration of substrate increases the amount of product produced until the enzyme molecules are working at maximum capacity.

Question 44

What does increasing the enzyme concentration do?

Answer 44

Increasing the amount of enzymes increases the amount of products produced until the substrate is depleted or until the product starts to inhibit enzyme action.

Question 45

What are enzyme concentrations regulated by?

Answer 45

• Controlling the production of the protein.
• Breaking down the enzyme.
• Activating the enzyme in response to a stimulus.

Question 46

What are enzyme inhibitors?

Answer 46

Some enzymes have two or more active binding sites. These enzymes can move between active states (when activation molecules bind with them) or inactive states (when inhibitors bind with them).

Question 47

What is feedback inhibition?

Answer 47

When the product of a reaction inhibits enzyme activity.

Question 48

How does feedback inhibition occur?

Answer 48

If a large amount of product is present it can act as an inhibitor by binding to the active site making the enzyme no longer able to bind to its substrate.

Question 49

Why does feedback inhibition occur?

Answer 49

To control the concentration of products in a cell.

Question 50

What are the two types of inhibitors?

Answer 50

• Competitive
• Non-competitive

Question 51

What are competitive inhibitors?

Answer 51

Competitive inhibitors have the same share as the enzyme’s substrate and can block the active site.

Question 52

What are non-competitive inhibitors?

Answer 52

Non-competitive inhibitors can attach to other sites on the enzyme and cause the shape of the active site to change.

Question 53

What are co-factors?

Answer 53

Small inorganic substances e.g. magnesium or zinc ions.

Question 54

What are co-enzymes?

Answer 54

Non-protein, organic substances that are required for enzyme activity. Small compared to the enzymes. Can be made from dietary vitamins and act as carriers of substances to and from reactants that are catalysed by enzymes.

Question 55

What do co-factors and co-enzymes do?

Answer 55

Some enzymes are inactive until they bind with other molecules or ions that change their conformation. This alters the shape and charge of the enzyme so it can capture substrates and react more efficiently.