CH 13.1: Bioenergetics and Thermodynamics

What is the first law of thermodynamics?

Energy may change form or be transported to a different region, but can’t be created or destroyed

What is the second law of thermodynamics?

Entropy of the universe increases

What is the reacting system?

Collection of matter undergoing a particular chemical or physical process

What is the universe made of?

Reacting system and its surroundings

What type of system are living organisms?

Open systems; exchanging material and energy with their surroundings

Are living organisms at equilibrium with their surroundings?

No

What is free energy (G)?

Amount of energy capable of doing work during a reaction at constant temperature and pressure

What does it mean if ΔG is negative?

Release free energy

What sign is ΔG if its exergonic?

Negative

What does it mean if ΔG is positive?

Gains free energy

What sign is ΔG if its endergonic?

Positive

What is enthalpy (H)?

Heat content of the reacting system. Reflects the number and kinds of chemical bonds in reactants and products.

What does it mean if ΔH is negative?

Chemical reaction releases heat; heat content of products is less than that of reactants

What does it mean if ΔH is positive?

Takes up heat from surroundings; heat content of products is more than that of reactants

What sign does ΔH have if its exothermic?

Negative

What sign does ΔH have if its endothermic?

Positive

What is entropy (s)?

A quantitative expression for randomness or disorder in a system

What does a positive ΔS mean?

Randomness is increasing

What does a negative ΔS mean?

Randomness is decreasing

What signs for ΔH, ΔS, and ΔG are favorable and why ?

• ΔH negative; releasing energy

• ΔS positive; increasing randomness

• ΔG negative; releasing free energy (reaction can occur spontaneously/ doesn’t need energy for reaction to occur)

Does entropy need to increase in the reacting system?

No, just in the universe

What is the process of energy flow in living organisms?

Living organisms take free energy from surroundings in the form of nutrients or sunlight and return energy as heat and entropy to its surroundings

What does heat mean in chemistry?

Is the transfer of thermal energy between systems due to temperature difference

What type of system is a cell?

Isothermal

Why is heat flow not a source of energy for cells?

Heat can only do work as it passes to a zone or object at lower temperature. Cells are isothermal, so there is no heat flow.

Why does heat do work as it passes to a zone or object at lower temperature?

Heat naturally flows from high to low temperature causing a large difference in value which allows work

What are heterotrophic cells?

Acquires free energy from nutrients

What are photosynthetic cells?

Acquires free energy from solar radiation

What do both heterotrophic and photosynthetic cells do?

Both cells transform free energy into ATP and other energy rich compounds

What does the magnitude of ΔG represent?

The distance from equilibrium

What does standards free-energy (ΔG°) mean?

It is the force driving the system to equilibrium at standard conditions (298K, 1M, 1atm)

What is the biochemistry standard state of:

• [H⁺]

• [H₂O]

• [Mg²⁺]

• [H⁺] = 10⁷ M

• [H₂O] = 55.5 M

• [Mg²⁺] = 1 mM

What are standard transformed constants?

physical constants based on biochemical standard state (written with a prime)

What do scientist do instead of adding H⁺ , H₂O, and Mg²⁺ concentrations into reactant and product equations?

It is incorporated into K^’_eq and ΔG^’°

What is ΔG^’° in terms of K^’_eq

ΔG^’° = -RT ln (K^’_eq)

If K^’_eq is…, what is ΔG^’° and what happens to the reaction?

• K^’_eq = 1

• K^’_eq > 1

• K^’_eq < 1

• K^’_eq = 1, ΔG^’° is Zero, Reaction is at equilibrium

• K^’_eq > 1, ΔG^’° is Negative, Reaction is moving forward

• K^’_eq < 1, ΔG^’° is Positive, Reaction is moving reverse