Chapter Overview: Chemistry Comes Alive

This chapter introduces the essential chemical principles that underpin the study of anatomy and physiology. Understanding the structure of atoms, elements, and molecules is fundamental to comprehending biological processes in the human body.

Levels of Biological Organization

Hierarchy of Organization

• Atoms: The smallest units of matter that retain the properties of an element.

• Molecules: Combinations of two or more atoms held together by chemical bonds.

• Cells: The basic structural and functional units of life.

• Tissues: Groups of similar cells performing a common function.

• Organs: Structures composed of two or more tissue types working together.

• Organ Systems: Groups of organs that perform related functions.

• Organism: An individual living being.

Elements and Atoms

Definition and Importance

• Element: A substance that cannot be broken down into simpler substances by ordinary chemical means.

• Atom: The smallest unit of an element that retains its chemical properties.

• Each element is defined by the number of protons in its nucleus (atomic number).

Subatomic Particles

• Proton: Positively charged particle in the nucleus.

• Neutron: Neutral particle in the nucleus.

• Electron: Negatively charged particle orbiting the nucleus.

States of Matter

• Solid: Definite shape and volume.

• Liquid: Definite volume, shape conforms to container.

• Gas: No definite shape or volume; expands to fill container.

Energy in Biological Systems

Definition and Forms

• Energy: The capacity to do work or put matter into motion.

• Kinetic Energy: Energy of motion.

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

Forms of Energy

• Chemical Energy: Stored in bonds of chemical substances.

• Electrical Energy: Movement of charged particles.

• Mechanical Energy: Directly involved in moving matter.

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

Energy Transformations

• Energy can be converted from one form to another (e.g., chemical to electrical).

• Some energy is lost as heat during conversions, making processes less efficient.

Chemical Elements in the Human Body

Major Elements

• Four elements make up about 96% of body mass: Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N).

• Other essential elements include calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, and iron.

Periodic Table Overview

• Elements are organized by increasing atomic number.

• Groups (columns) share similar chemical properties.

Properties of Elements

• Atomic Number: Number of protons in the nucleus.

• Atomic Mass: Average mass of all isotopes of an element (sum of protons and neutrons).

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

Isotopes and Radioactivity

Isotopes

• Isotopes have the same number of protons but different numbers of neutrons.

• Example: Carbon-12 (6 protons, 6 neutrons), Carbon-14 (6 protons, 8 neutrons).

Radioactive Isotopes

• Unstable isotopes that decay, emitting radiation.

• Used in medical imaging (e.g., PET scans) and cancer treatment.

• Can be hazardous due to radiation exposure.

Atomic Number and Mass Number

• Atomic Number (Z): Number of protons in an atom.

• Mass Number (A): Total number of protons and neutrons.

Formula:

Electron Distribution and the Bohr Model

Bohr Model

• Electrons orbit the nucleus in specific energy levels (shells).

• First shell holds up to 2 electrons; second shell up to 8 electrons.

Rules for Electron Distribution

• Electrons fill the lowest energy levels first.

• Each shell must be filled before electrons are added to the next shell.

Octet Rule and Chemical Reactivity

• Atoms are most stable when their outermost electron shell is full (usually 8 electrons).

• Atoms will gain, lose, or share electrons to achieve a full outer shell.

Chemical Bonds

Types of Bonds

• Ionic Bonds: Transfer of electrons from one atom to another, resulting in oppositely charged ions that attract each other.

• Covalent Bonds: Sharing of electron pairs between atoms.

Example: Sodium (Na) donates an electron to chlorine (Cl), forming Na+ and Cl- ions, which are held together by ionic bonds to form NaCl (table salt)/.

Summary Table: Key Atomic Properties

Applications in Anatomy & Physiology

• Radioactive isotopes are used in diagnostic imaging and cancer therapy.

• Understanding chemical bonds is essential for studying biomolecules and metabolic reactions.

Additional info: This summary expands on the provided slides by adding definitions, examples, and context for key terms and concepts relevant to introductory anatomy and physiology.