UNIT3 - AOS 2 - Biochemical pathways & Enzymes

Question 1

What is a biochemical pathway?

Answer 1

A series of linked reactions starting with an initial reactant that is converted in steps to a final product. Each step requires activity of specific enzymes.

Question 2

Anabolic pathways

Answer 2

• Simple molecules to complex molecules
• Energonic = requires energy
• Photosynthesis

Question 3

Catabolic Pathways

Answer 3

• Complex molecules to simple molecules
• Exergonic = releases energy
• Cellular respiration

Question 4

What is metabolism?

Answer 4

The total activity of the reactions of all biochemical pathways in a living organism
= Anabolism + Catabolism

Question 5

how are enzymes involved in biochemical pathways

Answer 5

they are composed of proteins and their key role is to act as a catalyst of the reactions in the biochemical pathways.

Question 6

5 key features of enzymes

Answer 6

1. REUSABLE (the enzyme doesn’t break up after catalysing the reaction)
2. SPECIFIC (most bind to 1 specific substrate)
3. REVERSIBLE (anabolic and catabolic - most)
4. SPEED UP NOT CREATE (catalyse reactions, not creating them)
5. ACTIVE SITE (Substrate binds to - specific to substrate - complementary shape)

Question 7

Enzyme-catalyst reaction

Answer 7

1. Substrate enters active site = enzyme-substrate complex
2. Reaction occurs
3. Products leave active site of enzyme

Question 8

Activation energy

Answer 8

Enzymes increase the rate of the biochemical reaction by decreasing activation energy.

Catabolic = Exergonic = release energy
Anabolic = Endogenic = requires energy

Question 9

How does temperature affect reaction rate

Answer 9

Denature: when an enzyme gets too hot (past optimal temp) it can denature and stop functioning.

Question 10

How does pH impact reaction rate

Answer 10

As pH increases or decreases from optimum, the rate of reaction and activity would decrease. Each enzyme has a different optimum pH.

Question 11

How does substrate concentration impact reaction rate

Answer 11

At very start, increases in substrates may increase reaction if there are enzymes with free active sites.
- However once all available enzymes are involved in the reactions and proceeding at a steady rate —> any further increase in the substrate concentration will not increase RR.

Question 12

How does enzyme concentration impact reaction rate.

Answer 12

Reaction rate will increase (if substrate remains constant)
- If increase in enzymes to a reaction the reaction rate will continue to increase until all substrates are used.

(* increased enzyme concentration = no effect on total amount of product made)

Question 13

How does irreversible inhibition impact the rate of reaction

Answer 13

= Substance uses covalent bonds to bind to enzymes active site = permanent. (enzyme can no longer bind to a substrate -> active site is blocked)

e.g. poison interfering with enzyme activity.

Question 14

How does reversible inhibition impact the rate of reaction

Answer 14

= Substance binds to active site but is not permanent (inhibitor can detach itself

COMPETITVE INHIBITOR
Inhibitor with similar shape to enzyme-substrate = bind to AS
= Enzyme=substrate complex cant be formed

NON-COMPETITIVE INHIBITOR
Inhibitor molecule doesn’t bind to AS, but binds to diff part of enzyme = ALLOSTERIC SITE
= Distorts enzymes shape of AS so substrate can no longer bind.