Chemistry Comes Alive: Foundations for Anatomy & Physiology

Chemistry Comes Alive

Why Chemistry Matters

Chemistry forms the basis of all life processes, underpinning every function in the human body. Understanding chemical principles is essential for grasping how breathing, muscle contraction, digestion, and nerve signaling occur.

• Chemistry is the study of matter and the changes it undergoes.

• All physiological processes involve chemical reactions.

Matter and Energy

Matter and energy are fundamental concepts in chemistry and biology. Matter is anything that occupies space and has mass, while energy is the capacity to do work.

• Matter: Exists in three states: solid, liquid, and gas.

• Energy: The ability to do work; exists as kinetic (in motion) and potential (stored).

• Major energy forms:

  • Chemical energy: Stored in bonds of molecules (e.g., ATP).

  • Electrical energy: Movement of charged particles (e.g., nerve impulses).

  • Mechanical energy: Directly involved in moving matter (e.g., muscle contraction).

  • Radiant energy: Energy of electromagnetic waves (e.g., sunlight).

Atoms and Elements

Atoms are the smallest units of matter, and elements are pure substances composed of only one type of atom. The human body is primarily made up of four elements.

• Atom: Consists of subatomic particles:

  • Protons: Positive charge, located in the nucleus.

  • Neutrons: Neutral charge, located in the nucleus.

  • Electrons: Negative charge, orbit the nucleus.

• Elements: Unique substances defined by their atomic number.

  • Major elements in the body: Oxygen, Carbon, Hydrogen, Nitrogen (constitute 96% of body mass).

Molecules, Compounds, and Mixtures

Molecules and compounds are formed by chemical bonding, while mixtures are physical blends of substances.

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

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

• Mixture: Physical combination of substances; types include:

  • Solutions: Homogeneous mixtures (e.g., saline).

  • Colloids: Heterogeneous mixtures with larger particles (e.g., cytosol).

  • Suspensions: Mixtures with visible particles that settle (e.g., blood).

Chemical Bonds

Chemical bonds hold atoms together in molecules and compounds. The three main types are ionic, covalent, and hydrogen bonds.

• Ionic bonds: Formed by transfer of electrons; results in charged ions (e.g., NaCl).

• Covalent bonds: Formed by sharing electrons; can be:

  • Nonpolar: Equal sharing (e.g., O2).

  • Polar: Unequal sharing, creating partial charges (e.g., H2O).

• Hydrogen bonds: Weak attractions between polar molecules; important in water and DNA structure.

Chemical Reactions

Chemical reactions involve the making and breaking of bonds. The main types are synthesis, decomposition, and exchange reactions.

• Synthesis (Anabolism): Building larger molecules from smaller ones.

  • General equation: $A + B \rightarrow AB$

• Decomposition (Catabolism): Breaking down molecules into smaller units.

  • General equation: $AB \rightarrow A + B$

• Exchange: Bonds are both broken and formed.

  • General equation: $AB + C \rightarrow AC + B$

• Factors affecting reaction rates:

  • Temperature (higher = faster)

  • Concentration (higher = faster)

  • Particle size (smaller = faster)

  • Catalysts (enzymes speed up reactions)

Inorganic Compounds

Inorganic compounds such as water, salts, acids, and bases are essential for body function and homeostasis.

• Water: Universal solvent, regulates temperature, cushions organs, participates in chemical reactions.

• Salts: Electrolytes; important for nerve and muscle function.

• Acids and Bases: Affect pH; acids release H+, bases accept H+.

  • pH scale: Ranges from 0 (acidic) to 14 (basic); neutral is 7.

Organic Compounds

Organic compounds contain carbon and are vital for life. The main classes are carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates: Sugars and starches; provide energy.

• Lipids: Fats; energy storage, insulation, cell membranes.

• Proteins: Structure and function; enzymes, hormones, transport.

• Nucleic Acids: DNA (genetic code), RNA (protein synthesis).

Dehydration Synthesis and Hydrolysis

These are key reactions in forming and breaking down organic molecules.

• Dehydration synthesis: Joins molecules by removing water.

• Hydrolysis: Breaks molecules apart by adding water.

Protein Structure

Proteins have four structural levels, each contributing to their function.

• Primary: Sequence of amino acids.

• Secondary: Alpha helices and beta sheets (hydrogen bonding).

• Tertiary: 3D folding due to interactions among R groups.

• Quaternary: Multiple polypeptide chains joined together.

Enzyme Action

Enzymes are proteins that catalyze chemical reactions by lowering activation energy.

• Enzyme: Biological catalyst; speeds up reactions without being consumed.

• Activation energy: Minimum energy required for a reaction.

Nucleic Acids: DNA vs. RNA

DNA and RNA are nucleic acids with distinct roles in cells.

• DNA: Double-stranded; stores genetic information.

• RNA: Single-stranded; involved in protein synthesis.

ATP – Energy Currency

ATP (Adenosine Triphosphate) is the primary energy carrier in cells, produced from glucose metabolism.

• ATP: Powers nearly all cellular processes.

• Structure: Adenine, ribose, three phosphate groups.

• Equation for ATP hydrolysis:

  • $ATP + H_2O \rightarrow ADP + P_i + energy$

Comparison Table: Types of Chemical Bonds

Bond Type	Mechanism	Example	Strength
Ionic	Transfer of electrons	NaCl	Moderate
Covalent (Nonpolar)	Equal sharing of electrons	O2	Strong
Covalent (Polar)	Unequal sharing of electrons	H2O	Strong
Hydrogen	Weak attraction between polar molecules	Between water molecules, DNA strands	Weak

Summary Table: Major Elements in the Human Body

Element	Symbol	Approximate % Body Mass	Function
Oxygen	O	65%	Cellular respiration, water component
Carbon	C	18%	Organic molecules, backbone of life
Hydrogen	H	10%	Water, organic molecules
Nitrogen	N	3%	Proteins, nucleic acids

Example: Water's polarity allows it to dissolve salts and other polar molecules, making it essential for transport and chemical reactions in the body.

Example: ATP hydrolysis releases energy for muscle contraction and nerve impulse transmission.