4 Energy and Thermodynamics in Biology Free Online FlashCards

What is mechanical work?

Work is energy transferred when a force causes displacement; for a constant force along the motion, $W = Fd$.

What is power, and how is it measured?

Power is the rate of doing work: $P = W/t$. It is measured in watts, with $1\,\mathrm{W} = 1\,\mathrm{J/s}$.

How do heat and temperature differ?

Heat is energy transferred because of a temperature difference; temperature describes a system’s thermal state. Heat is energy in transit, not energy stored in an object.

What are four ways heat moves between a patient and the surroundings?

Heat moves by conduction, convection, radiation, and evaporation. Evaporation removes heat when sweat changes from liquid to vapor.

Why is an organism an open system?

An organism is an open system because it exchanges both matter and energy with its surroundings.

What is the first-law energy balance for a closed system?

For a closed system, $\Delta U = Q - W$, where heat added is positive and work done by the system is positive.

What must an organism’s complete energy balance include?

An organism’s energy balance must include energy entering and leaving with matter as well as energy transfers such as heat and work.

What does the second law of thermodynamics state?

The total entropy of an isolated system does not decrease.

How can organisms maintain local organization without violating the second law?

Organisms can maintain local organization by taking in usable energy and releasing heat and waste, which increases the entropy of their surroundings.

What does negative Gibbs free-energy change indicate?

At constant temperature and pressure, $\Delta G = \Delta H - T\Delta S$. A negative $\Delta G$ indicates a thermodynamically favorable direction, but not how quickly the reaction occurs.

How does ATP help drive cellular tasks?

Cells couple reactions that release free energy, often ATP hydrolysis, to reactions requiring energy. ATP transfers usable free energy; it is not an independent energy source.

What happens to metabolic energy during exercise?

Metabolism converts nutrient chemical energy into usable forms, cellular processes, and heat. During exercise, increased muscle energy use raises both mechanical work and heat production.