Chemistry Comes Alive: Foundations for Human Anatomy & Physiology

Chapter 2: Chemistry Comes Alive

Introduction to Chemistry in Physiology

Chemistry is fundamental to understanding physiological processes in the human body. All bodily functions, from movement to digestion, are governed by chemical reactions and interactions. This chapter provides foundational knowledge of basic chemistry and biochemistry, essential for further study in anatomy and physiology.

Basic Chemistry

2.1 Matter and Energy

Matter and energy are the two primary concepts in chemistry. Matter is anything that has mass and occupies space, and it exists in three states: solid, liquid, and gas. Energy is the capacity to do work or put matter into motion, and it exists in kinetic (active) and potential (stored) forms.

• States of Matter: Solid (definite shape and volume), Liquid (changeable shape, definite volume), Gas (changeable shape and volume).

• Forms of Energy: Chemical (stored in bonds), Electrical (movement of charged particles), Mechanical (moving matter), Radiant/Electromagnetic (travels in waves).

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

Atoms and Elements

2.2 Atoms and Elements

All matter is composed of elements, which are substances that cannot be broken down by ordinary chemical methods. The human body is primarily composed of four elements: carbon, oxygen, hydrogen, and nitrogen. Atoms are the smallest units of elements, consisting of protons, neutrons, and electrons.

• Atomic Structure: Protons (+), Neutrons (0), Electrons (-). Protons and neutrons are in the nucleus; electrons orbit the nucleus.

• Atomic Number: Number of protons in the nucleus.

• Mass Number: Total number of protons and neutrons.

• Isotopes: Variations of elements with different numbers of neutrons.

• Atomic Weight: Average mass of all isotopes of an element.

Combining Matter: Molecules, Compounds, and Mixtures

2.3 Molecules and Compounds

Atoms combine to form molecules and compounds. A molecule is two or more atoms bonded together, while a compound is a molecule with different kinds of atoms.

• Molecule: H2, O2

• Compound: C6H12O6 (glucose)

Mixtures

Mixtures are combinations of two or more substances physically intermixed. There are three types: solutions, colloids, and suspensions.

• Solutions: Homogeneous mixtures; solute particles are very tiny and do not settle out.

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

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

Type	Solute Particle Size	Settling	Example
Solution	Very tiny	No	Mineral water
Colloid	Larger	No	Jell-O
Suspension	Very large	Yes	Blood

Differences Between Mixtures and Compounds

• Mixtures do not involve chemical bonding; compounds do.

• Mixtures can be separated by physical means; compounds require breaking chemical bonds.

• Mixtures can be heterogeneous or homogeneous; compounds are always homogeneous.

Chemical Bonds

2.4 Types of Chemical Bonds

Chemical bonds are energy relationships between electrons of reacting atoms. The three major types are ionic, covalent, and hydrogen bonds.

• Ionic Bonds: Transfer of electrons between atoms, forming ions (cations and anions).

• Covalent Bonds: Sharing of electrons between atoms. Can be polar (unequal sharing) or nonpolar (equal sharing).

• Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom.

Type	Description	Strength
Covalent	Sharing of pairs of electrons	Strongest
Ionic	Attraction between oppositely charged ions	Intermediate
Hydrogen	Attraction between partial charges	Weakest

Chemical Reactions

2.5 Types of Chemical Reactions

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

• Synthesis (Combination): A + B → AB (anabolic)

• Decomposition: AB → A + B (catabolic)

• Exchange: AB + C → AC + B (both synthesis and decomposition)

• Redox (Reduction-Oxidation): Involves electron transfer; reduction is gain, oxidation is loss.

Reactions can be exergonic (release energy) or endergonic (absorb energy). The rate of reaction is influenced by temperature, concentration, particle size, and catalysts (enzymes).

Biochemistry: Organic and Inorganic Compounds

2.6 Inorganic Compounds

Inorganic compounds include water, salts, acids, and bases. Water is the most abundant and important, with properties such as high heat capacity, high heat of vaporization, polar solvent properties, reactivity, and cushioning.

• Salts: Ionic compounds that dissociate in water, forming electrolytes.

• Acids: Proton donors; release H+ ions.

• Bases: Proton acceptors; release OH- ions.

• pH Scale: Measures concentration of H+ ions; ranges from 0 (acidic) to 14 (basic).

• Buffers: Resist changes in pH by binding or releasing H+ ions.

2.7 Organic Compounds: Synthesis and Hydrolysis

Organic molecules contain carbon and are unique to living systems. Major classes include carbohydrates, lipids, proteins, and nucleic acids. Many are polymers, synthesized by dehydration synthesis and broken down by hydrolysis.

Class	Monomer	Polymer
Carbohydrates	Monosaccharides	Polysaccharides
Proteins	Amino acids	Polypeptides/proteins
Nucleic acids	Nucleotides	DNA/RNA

Carbohydrates

2.8 Carbohydrates

Carbohydrates include sugars and starches, containing C, H, and O in a 2:1 ratio. They are classified as monosaccharides (single sugars), disaccharides (double sugars), and polysaccharides (many sugars).

• Monosaccharides: Simple sugars (glucose, ribose, deoxyribose).

• Disaccharides: Sucrose, maltose, lactose; formed by dehydration synthesis.

• Polysaccharides: Starch (plants), glycogen (animals); storage forms.

Lipids

2.9 Lipids

Lipids are hydrophobic molecules containing C, H, O, and sometimes P. Main types include triglycerides, phospholipids, and steroids.

• Triglycerides: Three fatty acids bonded to glycerol; function in energy storage, insulation, and protection.

• Saturated Fatty Acids: Single bonds, solid at room temperature.

• Unsaturated Fatty Acids: Double bonds, liquid at room temperature.

• Phospholipids: Modified triglycerides; important in cell membranes.

• Steroids: Four ring structures; cholesterol is the most important.

Proteins

2.10 Proteins

Proteins are polymers of amino acids, held together by peptide bonds. They have diverse functions, including structural, enzymatic, and contractile roles. Protein structure is determined by four levels: primary, secondary, tertiary, and quaternary.

• Fibrous Proteins: Structural, water-insoluble, stable (e.g., collagen).

• Globular Proteins: Functional, water-soluble, sensitive to environment (e.g., enzymes, antibodies).

• Denaturation: Loss of 3D shape and function due to pH or temperature changes.

Enzymes

Enzymes are globular proteins that act as biological catalysts, lowering activation energy and speeding up reactions. They are specific to substrates and are not consumed in the reaction.

• Enzyme Action Steps:

  1. Substrate binds to enzyme's active site.

  2. Substrate is rearranged to form product.

  3. Product is released.

Nucleic Acids

2.11 Nucleic Acids

Nucleic acids (DNA and RNA) are polymers of nucleotides, which consist of a nitrogen base, pentose sugar, and phosphate group. DNA is the genetic blueprint, while RNA links DNA to protein synthesis.

Characteristic	DNA	RNA
Major cellular site	Nucleus	Cytoplasm
Function	Genetic material; directs protein synthesis	Carries out genetic instructions
Structure	Double helix	Single strand
Sugar	Deoxyribose	Ribose
Bases	A, G, C, T	A, G, C, U

ATP: Cellular Energy

2.12 ATP (Adenosine Triphosphate)

ATP is the primary energy carrier in cells, capturing energy released from glucose breakdown. Its structure consists of an adenine-containing RNA nucleotide with two additional phosphate groups. The terminal phosphate can be transferred to other compounds to do cellular work.

• ATP → ADP: Loss of one phosphate group.

• ADP → AMP: Loss of a second phosphate group.