4. Biochemical Pathways

Question 1

How do enzymes affect speed

Answer 1

Enzymes are capable of speeding up (catalysing) biochemical reactions within the cell. Therefore they are called biological catalysts

Question 2

What are enzymes made up of

Answer 2

Enzymes are proteins made up of a single chain of amino acids folded to form specific 3D shape determine by the order number and type of amino acids that make up the chain.

Question 3

What is an active site?

Answer 3

Typically a small pocket or cleft in an enzyme is an active site (substrate binding site). The substrate of an enzyme is the molecule it acts on/input to an enzyme reaction. The output of an enzyme catalysed is the product. Substrates have a complementary shape to the active site.

Question 4

Lock and key model

Answer 4

The substrate fits into the active site of the enzyme perfectly like a lock and key. The substrate is structurally complementary to the active site. The model assumes the active site is rigid and fixed.

Question 5

Induced fit model

Answer 5

The active site of the enzyme changes shape slightly to fit the substrate. The active site of an enzyme has a defined shape but also a degree of flexibility

Question 6

Cellular metabolism

Answer 6

The sum of chemical reactions that occur in a living cell.

Question 7

Anabolic reactions and endergonic reactions

Answer 7

Anabolic reactions are chemical reactions in which atoms and molecules are joined together to make more complex molecules. Energy is required to make new chemical bonds, therefore termed endergonic reactions.

Question 8

Catabolic reactions or EXERGONIC reactions

Answer 8

Catabolic reactions break down complex molecules into simpler molecules. They release energy and are termed EXERGONIC reactions

Question 9

Activation energy and enzymes

Answer 9

Enzymes are able to reduce the activation energy of a reaction, that is enzymes reduce the amount of energy required to begin the reaction they catalyse.

Question 10

How does temperature affect enzyme activity

Answer 10

As temperature increases molecules become more excited, have more kinetic energy, more collisions.
Increased collisions increases opportunity for substrate to bump into the enzyme, increasing rate of reaction.
If the temperature becomes too high the structure of the protein is permanently changed and the active site changes shape disrupting its tertiary source so the substrate cannot bind to it….denaturation

Question 11

Enzyme activity in low temperatures

Answer 11

Low temperatures means molecules have low kinetic energy, collisions between substrate and enzyme occur at slower rates.

Question 12

Psychrophiles

Answer 12

Enzymes that function at very low temperatures because the protein has a more flexible structure and requires less energy

Question 13

Effect of pH on enzyme concentration

Answer 13

Enzymes have an optimum ph range and are denatured by extreme pH levels

Question 14

Effect of substrate concentration on enzyme activity

Answer 14

As substrate concentration increases the rate of reaction increases as there is more substrate to bind with the active site of the enzyme. However at saturation point all the enzymes are occupied and the rate cannot get higher no matter how much substrate is present. The rate plateaus.

Question 15

Effect of enzyme concentration on enzyme activity

Answer 15

As enzyme concentration increases the rate of reaction increases as there are more enzymes for the substrate to bind to. However at saturation point all the available substrates are converted into products. Therefore the rate of reaction cannot get any higher no matter how much enzyme is present and the rate plateaus.

Question 16

Inhibitor

Answer 16

An enzyme inhibitor is a molecule that binds to an enzyme reducing its activity by interfering with the enzyme in some way.

Question 17

Irreversible inhibitors

Answer 17

Irreversible inhibition of an enzyme occurs when a compound binds covalently to one or more amino acids and alters the structure of the enzyme affecting it’s active site. This permanent inhibits the enzyme because the inhibitor to enzyme bond is so strong that the inhibition cannot be reversed by the addition of excess substrate,

Question 18

Reversible inhibitors

Answer 18

The enzyme is not permanent inhibited in reversible inhibition. Reversible inhibitors inactivate enzymes through non covalent interactions that con be reversed

Question 19

Competitive inhibitors

Answer 19

• have similar shape to the usual substrate for the enzyme and compete with the substrate for the active site. Competitors bind temporarily with the he active site
• the complex does not react further to form products
• it can be reversed by increasing substrate concentration so the substrate can outcompete the inhibitor

Question 20

Non competitive inhibitors

Answer 20

Do no attack to the active site, but to the allosteric site. Causes the 3D structure of the enzyme to change shape, changing shape of the active site and therefore can no longer catalyse the usual reaction

Question 21

Biochemical pathways

Answer 21

A biochemical process occurs when the chemical bonds of reactants are broken and atoms recombine to form new substances or products. Biochemical reactions go through a series of steps in which the product of one step becomes the reactant of the next

Question 22

End product inhibition

Answer 22

The presence of an allosteric binding site on an enzyme enables regulation of metabolic pathways to occur through a process termed end product inhibition (allosteric effect).
In a biochemical pathway the end product may act on an enzyme in the chain to regulate its own production
The end product of a biochemical pathway can act as an inhibitor

Question 23

Cofactors

Answer 23

Inorganic mineral ions, non proteins component that bind tightly to the enzyme. Can be considered helper molecules that are essential in biochemical transformations

Question 24

Coenzymes

Answer 24

Non protein organic vitamins that bind loosely to the enzyme. Do not form a permanent part of the enzymes structures and assist in the transfer of molecules. Act with enzymes to alter the rate of reaction.