Processes in organisms often involve both exergonic and endergonic components. a

Question

Processes in organisms often involve both exergonic and endergonic components.

a) Explain what is meant by exergonic and endergonic.

Exergonic: release of energy Endergonic: absorption of energy

b) All organisms are highly specialized to perform exergonic and endergonic processes together. Why is this? How does this help the organism?

c) The muscles in your leg contract, allowing your body to move up onto a step. Describe the exergonic and endergonic components of this action.

d) Your raised body has greater potential energy than before it was raised. Explain if this still obeys the 2nd law of thermodynamics.

Explanation / Answer

Hi,

a. Exergonic reactions give out energy to the surrounding. Endergonic reactions absorb energy from the surrounding. The dissipated energy need not be heat or temperature only.

Exergonic reactions are spontaneous events that give out large amount of energy. The bonds that are formed are stronger than the bonds broken. In exergonic reactions free energy of the system decreases and hence the standard free energy change (Delta G) is negative. Example mixing sodium ad chlorine to get table salt.

Endergonic reactions are non-spontaneous and energy has to be supplied from surrounding to initiate the reaction. These increases the Gibbs free energy of the system, hence delta G is positive. These absorb energy from the surrounding, which makes the chemical bonds weaker. Example includes, melting of ice into water.

b. The digestion of food occurs by either catabolism or by anabolism. Catabolism breaks down larger molecules into small one which is a spontaneous event or exergonic. The anabolism where larger molecules are built in the body, is endergonic reaction. Body has tightly regulated enzymes which coordinate these reactions. This helps the body to maintain the constant pool of ATP and other energy molecules in the cell. This is called equilibrium.

C. The contraction of leg which allows the body to move up a step requires energy. Thus it is not spontaneous event, ( Endergonic reaction). The ATP is spent to create contraction in the muscle and entropy in the system now increases. This is used to lift the body against gravity. The relaxation event after climbing one step is exergonic and spontaneous.

D. 2nd law of thermodynamics states that entropy of a system always increases. It also says that entropy of the universe can never be negative. The raised body has greater potential energy. This is a non spontaneous reaction which has resulted due to endothermic reaction. The entropy in an endothermic reaction always increases. Hence it is still obeying the 2nd law.

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.