Chemistry and Physiological Reactions

Introduction to Chemistry in Physiology

Chemistry is fundamental to all physiological processes in the human body, including movement, digestion, heart function, and nervous system activity. Understanding basic chemistry and biochemistry is essential for studying anatomy and physiology.

• Basic Chemistry: Focuses on the foundational principles of matter and energy.

• Biochemistry: Examines the chemical processes within and related to living organisms.

Matter and Energy

Definition and Properties of Matter

Matter is anything that has mass and occupies space. It can be observed, smelled, or felt, and its weight is determined by mass plus the effects of gravity.

• States of Matter:

  • Solid: Definite shape and volume.

  • Liquid: Changeable shape; definite volume.

  • Gas: Changeable shape and volume.

Energy and Its Forms

Energy is the capacity to do work or put matter into motion. Unlike matter, energy does not have mass or occupy space.

• Kinetic Energy: Energy in action.

• Potential Energy: Stored (inactive) energy.

• Transformation: Energy can be converted from potential to kinetic, such as stored energy being released to perform work.

Types of Energy

• Chemical Energy: Stored in the bonds of chemical substances.

• Electrical Energy: Results from movement of charged particles.

• Mechanical Energy: Directly involved in moving matter.

• Radiant/Electromagnetic Energy: Travels in waves (e.g., heat, visible light, ultraviolet light, X-rays).

Atoms and Elements

Elements and Their Importance

All matter is composed of elements, which are substances that cannot be broken down into simpler substances by ordinary chemical methods. The human body is primarily made up of four elements: carbon, oxygen, hydrogen, and nitrogen (96% of body mass).

• 9 elements make up 3.9% of body mass.

• 11 elements make up less than 0.01% of body mass.

• The periodic table lists all known elements.

Atoms: The Building Blocks of Elements

Elements are made up of atoms, which are the smallest particles of an element that retain its properties. Atoms are unique for each element and determine its physical and chemical characteristics.

• Atomic Symbol: One- or two-letter shorthand for each element (e.g., "O" for oxygen, "C" for carbon).

• Some symbols are derived from Latin names (e.g., "Na" for sodium, "K" for potassium).

Periodic Table of the Elements

The periodic table organizes elements by their atomic number and properties. It is a fundamental tool for understanding chemical behavior in biological systems.

Atomic Structure

Subatomic Particles

Atoms are composed of three main subatomic particles:

• Protons: Positive charge (+), 1 atomic mass unit (amu).

• Neutrons: No charge (0), 1 amu.

• Electrons: Negative charge (-), negligible mass (0 amu).

The number of protons equals the number of electrons in a neutral atom. Protons and neutrons are located in the nucleus, while electrons orbit the nucleus.

Atomic Number and Mass Number

• Atomic Number: Number of protons in the nucleus (e.g., Hydrogen = 1).

• Mass Number: Total number of protons and neutrons.

• Isotopes: Atoms of the same element with different numbers of neutrons.

Isotopes and Radioisotopes

Isotopes have the same atomic number but different mass numbers. Radioisotopes are unstable isotopes that decay, emitting radiation. They are used in medical diagnostics and treatments but can also be harmful.

Chemical Bonds

Types of Chemical Bonds

Chemical bonds are energy relationships between electrons of reacting atoms. The main types are:

• Ionic Bonds: Transfer of electrons from one atom to another, forming ions (cations and anions).

• Covalent Bonds: Sharing of electrons between atoms. Can be single, double, or triple bonds.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen in water).

Ionic Bonds

• Ions: Atoms that have gained or lost electrons and become charged.

• Cation: Positively charged ion (lost electrons).

• Anion: Negatively charged ion (gained electrons).

• Example: Sodium chloride (NaCl) is formed by the transfer of an electron from sodium to chlorine.

Covalent Bonds

• Nonpolar Covalent Bonds: Equal sharing of electrons (e.g., O2, CO2).

• Polar Covalent Bonds: Unequal sharing of electrons, resulting in partial charges (e.g., H2O).

• Dipole: Molecule with two poles of charge due to unequal electron sharing.

Hydrogen Bonds

• Attractive force between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

• Important in water's properties and in stabilizing large biological molecules (e.g., DNA, proteins).

• Example: Hydrogen bonding between water molecules gives water its high surface tension.

Chemical Reactions

Chemical Equations

Chemical reactions involve the formation, rearrangement, or breaking of chemical bonds. They are represented by chemical equations showing reactants and products.

• Molecular Formula: Indicates the types and numbers of atoms in a molecule (e.g., H2O, CO2).

• Balanced Equation: Shows equal numbers of each atom on both sides.

Types of Chemical Reactions

• Synthesis (Combination) Reaction: Atoms or molecules combine to form a larger, more complex molecule.

  • General equation:

• Decomposition Reaction: Molecule is broken down into smaller molecules or atoms.

  • General equation:

• Exchange (Displacement) Reaction: Involves both synthesis and decomposition; bonds are made and broken.

  • General equation:

Energy Flow in Chemical Reactions

• Exergonic Reactions: Release energy; products have less potential energy than reactants.

• Endergonic Reactions: Absorb energy; products have more potential energy than reactants.

Reversibility and Rate of Chemical Reactions

• Most biological reactions are not easily reversible due to energy requirements or removal of products.

• Reaction rate is affected by temperature, concentration of reactants, and particle size.

• Summary Table: Types of Chemical Bonds

Key Equations

• General Synthesis Reaction:

• General Decomposition Reaction:

• General Exchange Reaction:

Additional info: This guide covers foundational chemistry concepts essential for understanding physiological processes in anatomy and physiology. Mastery of these topics is critical for further study of cellular and molecular mechanisms in the human body.