BackChapter 2A: Chemistry Comes Alive – Foundations for Anatomy & Physiology
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Chemistry and Physiological Reactions
Introduction to Chemistry in Physiology
Chemistry is fundamental to understanding all physiological processes in the human body. Every function, from movement to digestion and neural activity, is governed by chemical interactions.
The human body is composed of many chemicals that interact in complex ways.
Chemistry underlies all physiological reactions, including:
Movement (muscle contraction)
Digestion (breakdown of nutrients)
Pumping of the heart (cardiac muscle activity)
Nervous system signaling (neurotransmitter release and uptake)
Matter and Energy
Definitions and Properties
Understanding matter and energy is essential for grasping how the body functions at the molecular and cellular levels.
Matter: Anything that has mass and occupies space.
Matter can be seen, smelled, and/or felt.
Weight: Mass plus the effects of gravity.
Energy: The capacity to do work or put matter into motion.
Energy does not have mass, nor does it take up space.
The greater the work done, the more energy is used up.
Forms of Energy
Kinetic and Potential Energy
Energy exists in two main forms, both of which are crucial in biological systems.
Kinetic energy: Energy in action (e.g., muscle contraction, nerve impulse transmission).
Potential energy: Stored (inactive) energy (e.g., energy stored in chemical bonds).
Energy can be transformed from potential to kinetic energy. For example, stored energy in food molecules is released during metabolism to power cellular activities.
Types of Energy in Biological Systems
Chemical energy: Stored in the bonds of chemical substances (e.g., ATP, glucose).
Electrical energy: Results from the movement of charged particles (e.g., ions moving across cell membranes).
Mechanical energy: Directly involved in moving matter (e.g., muscle contraction moving bones).
Radiant or electromagnetic energy: Travels in waves (e.g., heat, visible light, ultraviolet light, X-rays). This energy is important for processes such as vision and the synthesis of vitamin D in the skin.
Examples and Applications
Example of chemical energy: The breakdown of glucose during cellular respiration releases energy used to form ATP, the energy currency of the cell.
Example of electrical energy: The transmission of nerve impulses relies on the movement of sodium and potassium ions across neuronal membranes.
Example of mechanical energy: The contraction of skeletal muscles enables movement of the body.
Example of radiant energy: Sunlight (visible light) is necessary for vision and for the skin to produce vitamin D.
Additional info: In physiology, the conversion of energy from one form to another is governed by the laws of thermodynamics. The first law states that energy cannot be created or destroyed, only transformed. The second law states that energy transformations increase the entropy (disorder) of the universe, which is why living systems require a constant input of energy.
