• The direction of chemical reactions
• Gibbs free energy
• Hess' law
• Oxidation / Reduction

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A spontaneous reaction, the formation of rust, ferrugem:

4 Fe(s) + 3 O2(g) → 2 Fe2O3(s) ΔH° = - 824 KJ/mol

Is this reaction Endothermic or Exothermic ?

Another spontaneous reaction, ΔH° = -24 KJ/mol

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The direction of a chemical reaction:

ΔH° = +28 KJ/mol ΔS° = +109 KJ/mol

Spontaneity of chemical reactions

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Hess Law

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Hess Law example: Calculate ΔH for the following reaction:

We have the following information: We reverse the second reaction and multiply it by two:

We can remove molecules that are present on both sides of the arrow:

The final reaction is the same as the one we wanted to analyze.

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The reaction: C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O is

1. Spontaneous at all temperatures.
2. Spontaneous OR non spontaneous depending on the temperature.
3. Non-spontaneous at all temperatures.

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What is the direction of each of the following reactions when the reactants are initially present in equimolar amounts? Use the data given below.

1. ATP + glycerol ⇄ glycerol 3 phosphate + ADP
2. ATP + pyruvate ⇄ phosphenolpyruvate + ADP
3. ATP+ glucose ⇄ glucose 6 phosphate + ADP
4. ATP + creatine ⇄ creatine phosphate + ADP

Compound	△G kJ/mol (hydrolysis)
Phosphoenolpyruvate (PEP)	-61.9
1,3-Bisphosphoglycerate(1,3-BPG)	-49.4
Creatine Phosphate	-43.1
ATP (to ADP)	-30.5
Glucose 1-Phosphate	-20.9
Pyrophosphate (PPi)	-19.3
Glucose 6-phosphate	-13.8
Glycerol 3-phosphate	-9.2

The concentrations of ATP, ADP and Pi differ with the cell type. Consequently, the release of free energy with ATP hydrolysis will vary with the cell type. Using the following table, calculate the ∆G for ATP hydrolysis in muscle, liver, and brain cells.

The concentration of ATP, ADP, and Pi differ with cell type. Consequently, the release of free energy with the hydrolysis of ATP will vary with cell type. Use the following table to calculate the ∆G for the hydrolysis of ATP in liver, muscle, and brain cells.

In which cell type is the free energy of ATP hydrolysis most negative?

∆G˚ for the hydrolysis of ATP is -30.5 kJ/mol. R = 8.315 J/(mol K). Assume a temperature of 37°C.

	ATP (mM)	ADP (mM)	Pi (mM)
Liver	3.5	1.8	5
Muscle	8	0.9	8
Brain	2.6	0.7	2.7

What are the main carbohydrates absorbed into the bloodstream after digestion of a piece of cake that contains flour, milk and sucrose as main ingredients.

The reaction C(s)diamond → C(s)graphite has a negative change in Gibbs free energy and is therefore thermodynamically favorable at 25 °C and 1 atmosphere of pressure. Why is diamond seemingly stable at these conditions?

Monensin is a Na+ ionophore. This compound is considered an antimicrobial agent, affecting glucose metabolism. Explain this phenomenon.

Explain the role of disaccharidases in the digestion of carbohydrates in the intestines of humans and animals and identify the main disaccharidases involved in this process.

Describe the absorption mechanisms of glucose in the small intestine, emphasizing the role of SGLT1, Glut-5 and GLUT transporters.

Compare and contrast the structural differences between cellulose, starch, and glycogen, and discuss how these differences impact their digestibility by human enzymes.

Glycogen is a highly branched molecule. Does this high level of branching provide any advantage?

This is an individual exercise for each student. As you now know, synthesizing ATP from ADP and Pi under standard conditions requires a total of 30.5 kJ/mol. However, the physiological concentrations of ATP, ADP, and Pi in cells differ from standard conditions. Calculate the free energy change of ATP hydrolysis at 25°C in cells where the concentrations of ATP, ADP, and Pi are different from the standard conditions. Find your values for ATP, ADP, and Pi in the TP35 spreadsheet.

Please answer in the same spreadsheet as as indicated for the first example student "Max Maximus".