Chemistry and Physiological Reactions

Introduction to Chemistry in Anatomy & Physiology

Chemistry is essential for understanding physiological processes in the human body. All living organisms rely on chemical reactions to maintain life, from cellular respiration to muscle contraction.

• Matter is anything that occupies space and has mass.

• Energy is the capacity to do work or cause change.

• Biochemistry is the study of chemical processes within living organisms.

2.1 Matter and Energy

Matter

Matter is the substance of the universe and is composed of elements and compounds. It can exist in three states: solid, liquid, and gas.

• Mass is the amount of matter in an object.

• Weight is mass plus the effects of gravity.

Energy

Energy is required to move matter and exists in various forms. It is classified as kinetic (energy in action) or potential (stored energy).

• Kinetic energy: Energy of motion.

• Potential energy: Stored energy due to position or structure.

• Energy can be converted from one form to another, but some is lost as heat.

Forms of energy:

• Chemical energy: Stored in 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., light, X-rays).

2.2 Atoms and Elements

Elements

Elements are unique substances that cannot be broken down by ordinary chemical means. Each element is defined by its atomic number.

• Atoms are the smallest units of elements that retain their properties.

• Major elements in the human body: oxygen, carbon, hydrogen, nitrogen.

Atoms

An atom consists of a nucleus (protons and neutrons) and electrons orbiting the nucleus.

• Protons: Positively charged particles in the nucleus.

• Neutrons: Uncharged particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

Common Elements Composing the Human Body

Structure of Atoms

Atoms are composed of a central nucleus containing protons and neutrons, surrounded by electrons in energy levels (shells).

• Atomic number: Number of protons in the nucleus.

• Mass number: Sum of protons and neutrons.

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

• Radioisotopes: Unstable isotopes that decay, emitting radiation.

2.3 Combining Matter

Molecules and Compounds

Molecules are formed when two or more atoms bond together. Compounds are molecules composed of two or more different elements.

• Molecule: Two or more atoms bonded together (e.g., O2).

• Compound: Two or more different atoms bonded together (e.g., H2O).

Mixtures

Mixtures are combinations of two or more substances that are physically intermixed but not chemically bonded.

• Solutions: Homogeneous mixtures; solute particles are very small.

• Colloids: Heterogeneous mixtures; solute particles are larger and do not settle out.

• Suspensions: Heterogeneous mixtures; solute particles are very large and settle out.

2.4 Chemical Bonds

Role of Electrons in Chemical Bonding

Electrons in the outermost shell (valence electrons) determine an atom's chemical behavior. Atoms bond to achieve a stable electron configuration.

• Octet rule: Atoms tend to gain, lose, or share electrons to achieve eight in their valence shell.

• Inert elements: Have complete valence shells and are chemically unreactive.

• Reactive elements: Do not have complete valence shells and tend to form bonds.

Types of Chemical Bonds

• Ionic bonds: Formed by transfer of electrons from one atom to another, creating ions (cations and anions).

• Covalent bonds: Formed by sharing electrons between atoms.

• Polar covalent bonds: Unequal sharing of electrons, resulting in partial charges.

• Nonpolar covalent bonds: Equal sharing of electrons.

• Hydrogen bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).

Example: Water (H2O) molecules are held together by polar covalent bonds, and hydrogen bonds form between adjacent water molecules.

2.5 Chemical Reactions

Chemical Equations

Chemical reactions involve the formation or breaking of chemical bonds. They are represented by chemical equations.

• Reactants: Substances entering into a reaction.

• Products: Substances resulting from the reaction.

General equation:

Types of Chemical Reactions

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

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

• Exchange reactions: Involve both synthesis and decomposition; parts of molecules are exchanged. Example:

Energy Flow in Chemical Reactions

• Exergonic reactions: Release energy.

• Endergonic reactions: Absorb energy.

Reversibility and Rate of Chemical Reactions

• Many chemical reactions are reversible.

• Rate of reaction is influenced by temperature, concentration, particle size, and catalysts.

• Catalysts (including enzymes) increase the rate of reactions by lowering activation energy.

Example: Enzymes in the body speed up metabolic reactions necessary for life.

Additional info:

• These notes provide foundational chemistry concepts essential for understanding physiological processes in Anatomy & Physiology.

• Tables and diagrams referenced in the slides have been recreated and expanded for clarity.