Unit 3 - Thermodynamics & Enzymes

Question 1

First Law of Thermodynamics

Answer 1

-energy can be transferred and transformed, but it cannot be created nor destroyed

Question 2

Second Law of Thermodynamics

Answer 2

-energy tends to disperse spontaneously

localized and ordered to spread out and disordered

Question 3

Exergonic Reactions

Answer 3

• occur spontaneously (gibbs free energy is negative)
• net release of energy
• energetically favourable reaction

Question 4

Endergonic Reactions

Answer 4

• does not occur spontaneously (gibbs free energy is positive)
• net input of energy required
• energetically unfavourable reaction

Question 5

Coupling of Reactions

Answer 5

• can occur if reactions share one or more intermediates
• unfavourable reaction can be driven by second, highly favourable reaction
• cells cannot undergo endergonic reactions, must find a way to do them exergonically

Question 6

Collisions are influenced by…

Answer 6

• how fast molecules are moving - temperature

- how crowded they are - concentration

Question 7

Enzymes

Answer 7

1. catalyze thermodynamically favourable reactions
2. allows reactions to proceed at rapid rates
3. accelerate and control rates of vitally important biochemical reactions
4. DO NOT CHANGE: thermodynamics, equilibrium, catalyze non-spontaneous reactions, endergonic reactions

Question 8

Activation Energy

Answer 8

-energy required for reaction to proceed/start

enzymes lower a.e. of exergonic reactions so that they can proceed

Question 9

Enzyme Cofactors

Answer 9

-some enzymes bind to non-protein factors to ‘help’ them do required chemistry they cannot do on their own
-inorganic & organic
chemically changed during the reaction
- must be regenerated to complete catalytic cycle

Question 10

Non-competitive inhibitors

Answer 10

-bind to allosteric sites, changing enzyme’s confirmation so that the substrate no longer fits

Question 11

Competitive inhibitors

Answer 11

-competes with substrate to bind to active site so that the substrate cannot bind

Question 12

Covalent Modification

Answer 12

• phosphorylation occurs at the -OH containing side chains
• to add phosphate group –> add kinase
• to remove phosphate group –> need phosphatase