3.1:
The First Law of Thermodynamics
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The first law of thermodynamics, also known as the law of conservation of energy, states that energy is always conserved. This means energy cannot be created or destroyed; however, energy can be transferred between objects or converted from one form of energy to another.
In thermodynamics, the universe is divided into two parts. The matter or region under study is the system, and everything other than the system is the surroundings.
Heat and work are two ways of energy transfer between the system and the surroundings.
The transmission of thermal energy is referred to as heat. When heat flows from the surroundings to the cell membrane, the movement of molecules in the membrane becomes more fluid, similar to ice melting.
Transmission of mechanical energy is referred to as work. Changes in the length of cytoskeletal filaments generate forces that can be transmitted as mechanical energy to push or pull on the cell membrane.
3.1:
The First Law of Thermodynamics
The first law of thermodynamics deals with the total amount of energy in the universe. It states that this total amount of energy is constant. In other words, there has always been, and always will be, exactly the same amount of energy in the universe. Energy exists in many different forms. According to the first law of thermodynamics, energy may transfer from place to place or transform into different forms, but it cannot be created or destroyed. The transfers and transformations of energy take place around us all the time. Light bulbs transform electrical energy into light energy. Gas stoves transform chemical energy from natural gas into heat energy. Plants perform one of the most biologically useful energy transformations on earth: that of converting sunlight energy into the chemical energy stored within organic molecules.
The challenge for all living organisms is to obtain energy from their surroundings in forms that they can transfer or transform into usable energy to do work. Living cells have evolved to meet this challenge very well. Chemical energy stored within organic molecules such as sugars and fats transforms through a series of cellular chemical reactions into energy within ATP molecules. Energy in ATP molecules is easily accessible to do work. Examples of the types of work that cells need to do include building complex molecules, transporting materials, powering the beating motion of cilia or flagella, contracting muscle fibers to create movement, and reproduction.
This text is adapted from Openstax, Biology 2e, Section 6.3: The Laws of Thermodynamics.