Metabolism (3A)

Question 1

Chemical Work

Answer 1

Synthesis of complex molecules from simple pre-cursor

Question 2

Transport Work

Answer 2

Moving nutrients in and waste out

Question 3

Mechanical Work

Answer 3

Cell division, motility, etc.

Question 4

Free Energy (Go)

Answer 4

Energy to do work

Question 5

Standard biochemical free energy (deltaGo’)

Answer 5

@ pH 7.0, 1 atm, 298K and 1M concentration

Question 6

-ve deltaGo’

Answer 6

Exergonic spontaneous reaction

Question 7

+ve deltaGo’

Answer 7

Endergonic, non-spontaneous

Question 8

Commonalities of metabolism

Answer 8

1) ATP conserves energy from exergonic reactions, and
this energy can be used to drive endergonic reactions
2) metabolic reactions are organized in pathways and
cycles
3) metabolic reactions are catalyzed by enzymes or
ribozymes
4) oxidation – reduction reactions are important for
energy conservation

Question 9

ATP

Answer 9

• traps a lot of the energy released in exergonic reactions, and this
can be used to drive endergonic reactions
• cellular currency
• hydrolyzes to ADP and orthophosphate, with ΔG°’ = ‐7.3 kcal / mol = ‐30.5 kJ / mol
• has a high transfer potential, and can donate phosphate to a molecule with a lower potential (eg: H2O)

Question 10

Enzymes

Answer 10

1) Increase rate of reaction in exergonic reactions
2) Speeds up reaction rate
3) Usually proteins but also RNAzymes

Question 11

Catalytic cycle of enzymes

Answer 11

1) Substrate is bound to enzyme active site
2) Enzyme substrate complex forms
3) Strain is placed on bond
4) Products are released
5) Enzyme is ready to begin new catalytic cycle

Question 12

Lock and Key

Answer 12

binding site is
complementary to the shape of the
substrate.
proposed by Emil Fischer in 1890

Question 13

Induced Fit

Answer 13

enzyme changes shape
upon substrate binding.
proposed by Daniel Koshland in 1958

Question 14

Competitive Inhibitor

Answer 14

looks like substrate, binds to enzyme

Question 15

Methotrexate

Answer 15

1000 fold lower binding
used for cancer therapy

Question 16

Penicillin

Answer 16

-Competition example
-Structural similiartiy with the natural substrate for glycopeptide transpeptidase
-Highly reactive
-Covalently modifies enzymes

Question 17

Three methods of regulation (metabolism)

Answer 17

1. Metabolic channelling (compartmentalization)
2. Amount of enzyme
3. Directly affecting enzyme activity (inhibitors and activators)

Question 18

Feedback Inhibition

Answer 18

-Excess product shuts off entire pathway
-Enzyme can be inhibited or modified to affect activity

Question 19

Allosteric regulator

Answer 19

Binds outside of active site and immediates reaction
-NOT COMPETITIVE because different products and non-covalent

Question 20

Phosphorylation

Answer 20

phosphate groups removed to modify

Question 21

Oxidation-reduction reactions

Answer 21

Electrons move from donor to acceptor
-Reaction is two half reactions, an oxidation and a reduction

Question 22

Electron donor

Answer 22

Reductant, reducing agent

Question 23

Electron acceptor

Answer 23

Oxidant, oxidising agent

Question 24

Standard Reduction Potential (E0’)

Answer 24

equilibrium constant that measure
the tendency for the donor to lose electrons, with standard conditions at pH 7 = E0’