Enzymes & Biochemical Pathways (4.1)

Question 1

State the two major characteristics of enzymes

Answer 1

1. Specificity

2. Catalytic Power

Question 2

Describe enzyme specificity

Answer 2

Different enzymes act as catalysts for specific biochemical reactions by binding to specific substrate.

Question 3

Some enzymes are able to act on multiple substrates. State whether this is true/false.

Answer 3

True. Enzymes can act on multiple substrates and catalyse multiple reactions.

Question 4

Define substrate

Answer 4

Molecule which an enzyme acts upon

Question 5

State whether or not enzymes are consumed when they catalyse reactions

Answer 5

No. Enzymes are not consumed when catalysing reactions.

Question 6

Define catalytic power

Answer 6

Potential of an enzyme to increase the rate of a biochemical reaction

Question 7

Describe what forms the enzyme active site

Answer 7

Tertiary protein folding

Question 8

Describe the active site

Answer 8

Complex 3D shape that interacts with a specific substrate to catalyse specific reaction/s.

Question 9

State what forms when the active site binds to the substrate

Answer 9

Enzyme-substrate complex

Question 10

State the 2 enzyme-substrate interaction models

Answer 10

1. Lock and key

2. Induced fit

Question 11

State what stabilises the presence of the substrate in the active site

Answer 11

• hydrogen bonds

- hydrophobic interactions

Question 12

Describe the lock and key model

Answer 12

The active site and substrate fit as a lock and key

Question 13

State the real-life object represented by the ‘lock’ in the lock and key model

Answer 13

The active site

Question 14

State the real-life object represented by the ‘key’ in the lock and key model

Answer 14

The substrate

Question 15

Describe the induced fit model

Answer 15

When a substrate binds to the active site of an enzyme, a conformational change occurs.

Question 16

Describe conformational change

Answer 16

A change in the 3D arrangement of atoms in a macromolecule (e.g. protein or nucleic acid).

Question 17

State whether or not some reactions can be catalysed in both directions

Answer 17

True. Some reactions can be catalysed in both directions

Question 18

Describe activation energy

Answer 18

The energy that is required to start a biochemical reaction

Question 19

Describe where the catalytic power of enzymes comes from

Answer 19

Ability to reduce activation energy

Question 20

Describe 3 ways that enzymes reduce activation energy

Answer 20

1. proximity and orientiation
2. micro-environment
3. ion exchange

Question 21

Describe the effect of enzymes on proximity and orientiation

Answer 21

Enzymes bring reactants closer to one another to increase collision potential.

Question 22

Describe the effect of enzymes on the micro-environment

Answer 22

Reaction environment becomes non-polar to allow stabilising interactions to occur

Question 23

Provide 3 examples of stabilising interactions which occur in non-polar environment

Answer 23

1. hydrogen bonding
2. hydrophobic interactions
3. van der Waals interactions

Question 24

Describe the effect of enzymes on ion exchange

Answer 24

Amino acids in the active site can often exchange H+ ions with the substrate.

Question 25

State the 3 major types of biochemical pathways

Answer 25

1. linear
2. branched
3. cycles

Question 26

Describe metabolism

Answer 26

Collection of all of the biochemical reactions that occur in living cells.

Question 27

State the 2 major types of metabolic reactions

Answer 27

1. catabolic

2. anabolic

Question 28

Describe catabolic reactions

Answer 28

Reactions in which the substrates are broken down and energy is released

Question 29

State whether catabolic reactions are exergonic or endergonic

Answer 29

Exergonic, because they release energy to break bonds between molecules.

Question 30

Describe anabolic reactions

Answer 30

Reactions that require an input of energy in order to produce larger molecules from smaller substrates.

Question 31

State whether anabolic reactions are exergonic or endergonic

Answer 31

Endergonic, because they require energy to form bonds between molecules.

Question 32

Describe reaction coupling

Answer 32

A reaction that releases energy will be coupled with a reaction that requires an input of energy

Question 33

State the 2 directions of biochemical reactions

Answer 33

substrate -> product

product -> substrate

Question 34

Describe the structure of most enzymes

Answer 34

Globular

Tertiary or quaternary folding

Question 35

Describe enzyme catalysis

Answer 35

Reactions are reversible and can be catalysed in both directions

Question 36

Provide an example of an anabolic reaction

Answer 36

Building glucose in photosynthesis

Question 37

Provide an example of a catabolic reaction

Answer 37

Breakdown of glucose in cellular respiration

Question 38

Describe what activation energy is abbreviated as

Answer 38

E,A

Question 39

Describe transition state

Answer 39

High-energy state which peaks after the desired activation energy has been added. Bonds must be broken in a reaction. For them to be broken molecules must be contorted to an unstable state

Question 40

State the common form of activation energy

Answer 40

Heat

Question 41

Describe the effect of heat on the behaviour of enzymes and substrates within a reaction

Answer 41

Thermal energy speeds up motion of reactants, increasing force and frequency of collisions allowing for bond breakage.

Question 42

Describe the general trend between activation energy and reaction rate

Answer 42

The higher the activation energy the slower the reaction rate

Question 43

Describe what the process of speeding up a reaction by reducing reaction rate is known as

Answer 43

catalysis

Question 44

Describe what the factor that is added to reduce activation energy is known as

Answer 44

catalyst

Question 45

Describe biological catalysts

Answer 45

enzymes