Second Half F24 II: Lecture Slides 18 - 31

Question 1

What is Adenosine Triphosphate?

Answer 1

The energy currency of the cell

Question 2

Who discovered ATP?

Answer 2

Fritz Lipmann

Question 3

What is ATP?

Answer 3

It is a nucleotide that consist of a base (adenosine), a sugar (ribose) and three phosphate groups labelled beta, alpha, gamma

Question 4

How much ATP would a 70kg person use?

Answer 4

Approximately 40kg during a restful day.

Question 5

How do cells use a catabolism (exergonic) breakdown in terms of ATP?

Answer 5

Cells breakdown nutrient molecules and use the available free energy to synthesize ATP from ADP

Question 6

How do cells use Anabolic (endergonic) in terms of ATP?

Answer 6

The ATP synthesized in a catabolic pathway, donates its free energy to the anabolic pathway for synthesis of macromolecules and metabolic intermediates, and active transport across membranes.

Question 7

What is the typical lifetime of an ATP molecule?

Answer 7

Seconds to minutes

Question 8

What happens in the hydrolysis of ATP?

Answer 8

ATP reacts with H2O to break bonds and form ADP

Question 9

What are most hydrolysis reactions?

Answer 9

They are favourable

Question 10

What does a Favourable Reaction Mean in terms of Delta G?

Answer 10

A reaction is thermodynamically favourable if the products have a lower Gibbs free energy than the starting materials.

Question 11

What does the value of Delta G depend on?

Answer 11

It depends on the nature of the bond being hydrolyzed

Question 12

What are the typical delta G values for amides, esters and phosphoesters?

Answer 12

15 - 20kJ/mol

Question 13

What is the Delta G for the Hydrolysis of ATP?

Answer 13

-50kJ/mol

Question 14

What does the Delta G0 ‘ value state?

Answer 14

The Gibbs free energy Value under Standard Conditions
- pH = 7
- Temperature = 25 C

Question 15

What is the Delta G0’ Value for ATP Hydrolysis?

Answer 15

-30.5kJ/mol

Question 16

Where does all of the energy releasing and energy requiring processing take place?

Answer 16

At the phosphates

Question 17

What does hydrolysis release?

Answer 17

The electrostatic repulsion among the negative charges

ATP –> ADP + Pi (neg. charge)

Question 18

What does the product inorganic phosphate have?

Answer 18

Due to its negative charge and low energy, it forms a better resonance stabilization than ATO

Question 19

What does a Negative Gibbs free energy?

Answer 19

That the reaction is favourable

Question 20

What is the equation for Delta G0’?

Answer 20

Free Energy of Products - Free Energy of Reactants

Question 21

How many Phosphoanhydride “high energy bonds” are there in ATP?

Answer 21

Two linkages in ATP

Question 22

What is the nucleophile in terms of the hydrolysis of ATP?

Answer 22

The Water

Question 23

What are the two nucleophile attacks within the hydrolysis of ATP?

Answer 23

1.) The gamma phosphate (electrophile) and the hydrolysis will be between the link between gamma and beta phosphate

2.) Hydrolysis of the a-B linkage (nucleophile attack on the a phosphate)

Question 24

How much energy does the hydrolysis of the gamma phosphate of ATP yield?

Answer 24

About -30kJ of energy (Delta G’0 = -30.5kJ)

Question 25

Which phosphate from ATP turns into the inorganic phosphate?

Answer 25

The gamma phosphate (leaving group)

Question 26

What is the reaction when the nucleophile attacks the a phosphate?

Answer 26

ATP to AMP + PPi

(yields AMP and pyrophosphate (PPi)

Question 27

What happens to PPi?

Answer 27

It is immediately hydrolyzed by the enzyme pyrophosphatase to give two moles of Pi (2Pi)

Question 28

What does the hydrolysis of PPi result in?

Answer 28

The hydrolysis of both the phosphoanhydride bonds.

Question 29

What is the free energy of the hydrolysis of ATP to AMP + 2Pi compared to the hydrolysis of ATP to ADP + 2Pi?

Answer 29

The hydrolysis to AMP takes twice as long releasing more energy due tp the breakage of more phospo anhdyride bonds (high energy)

Question 30

What is the Gibbs free energy of the Hydrolysis to AMP?

Answer 30

-64.8 kJ

Question 31

What type of reaction is the hydrolysis of ATP?

Answer 31

Exergonic due to the energy being released when the phosphoanhydride bonds break?

Question 32

What happens in the synthesis of Glutamine?

Answer 32

NH3 acts as a nucleophile and attacks the electrophilic C on the glutamate molecule, it uses the hydrolysis of ATP to form into Glutamine

Question 33

What is the first step of Glutamine Synthetase?

Answer 33

ATP reacts with Glutamate to produce a covalent intermediate, a mixed anhydride of phosphate and glutamate (enzyme bound intermediate)

Question 34

What is the second step of Glutamine Synthetase?

Answer 34

NH3 acting as a nucleophile, reacts with the electrophile carbonyl carbon atom. Pi, the leaving group is displaced.

Question 35

Why is ATP chemically versatile?

Answer 35

The phosphate group can participate in a variety of chemical reactions with common organic functional groups

Question 36

In addition to the phosphoric group, what can ATp also transfer?

Answer 36

PPi or AMP to a substrate or to an amino acid residue to drive certain reactions forward.

Question 37

What does ATP provide energy through?

Answer 37

Not simple hydrolysis but group transfer (simple hydrolysis loses energy)

Question 38

What is the Gibbs free energy of Pi

Answer 38

0

Question 39

What is the Gibbs free energy of the Hydrolysis of Glucose-6-phosphate?

Answer 39

-15 (low energy)

Question 40

What are some high energy compounds?

Answer 40

Acetyl-CoA, Creatine Phosphate, 1,3 - biphosphoglycerate, Phosphoenolpyruvate

Question 41

Why would ATP And GTP have similar Delta G Hydrolysis Values?

Answer 41

GTP is comparatively equivalent to ATP as it is also utilized as an energy source and phosphate donor in metabolic processes, however ATOP may have been chosen due to evolution purposes

Both Purines