Chapter 2: Basic Chemistry and Biochemistry for Anatomy & Physiology

Chapter 2: Basic Chemistry and Biochemistry

Chemical reactions are fundamental to all physiological processes. Understanding basic chemistry and biochemistry is essential for comprehending body functions in anatomy and physiology.

Basic Chemistry

Matter and Energy

Matter and energy are foundational concepts in chemistry and biology, underlying all physiological processes.

• Matter: Anything that has mass and occupies space. Examples: bones, blood plasma, air.

• Energy: The capacity to do work or put matter into motion. It does not have mass or occupy space.

• Major Forms of Energy:

  • Chemical Energy: Stored in chemical bonds; released or absorbed during chemical reactions. Example: ATP hydrolysis.

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

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

  • Radiant Energy: Energy carried by electromagnetic waves (e.g., visible light, X-rays).

  • Thermal Energy: Related to temperature and motion of particles.

  • Nuclear Energy: Stored in the nucleus of atoms, released during nuclear reactions.

• Potential Energy: Stored energy due to position or arrangement (e.g., chemical bonds, water behind a dam).

• Kinetic Energy: Energy of motion (e.g., moving muscles, flowing blood).

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

Elements and Atoms

Elements and atoms are the building blocks of matter, with specific properties that determine their behavior in biological systems.

• Chemical Element: A substance that cannot be broken down into simpler substances by ordinary chemical methods. There are 118 recognized elements.

• Major Elements in the Human Body:

  • Oxygen (O): 65.0% of body mass; essential for ATP production.

  • Carbon (C): 18.5% of body mass; found in all organic molecules.

  • Hydrogen (H): 9.5% of body mass; influences pH of body fluids.

  • Nitrogen (N): 3.2% of body mass; component of proteins and nucleic acids.

• Atoms: Smallest unit of an element, composed of subatomic particles:

  • Protons: Positive charge, located in the nucleus, mass ≈ 1 amu.

  • Neutrons: No charge, located in the nucleus, mass ≈ 1 amu.

  • Electrons: Negative charge, orbit the nucleus, mass ≈ 1/2000 amu.

• Atomic Number: Number of protons in the nucleus.

• Atomic Mass: Sum of protons and neutrons in the nucleus.

• Isotopes: Variants of elements with different neutron numbers.

• Radioisotopes: Unstable isotopes that exhibit radioactivity.

Molecules and Mixtures

Molecules and mixtures are combinations of atoms and substances, with distinct properties and biological significance.

• Molecule: Two or more atoms bonded together (e.g., O2, H2O).

• Compound: Chemically bonded molecules of different elements (e.g., NaCl).

• Mixture: Physically combined substances; components retain their properties.

• Types of Mixtures:

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

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

  • Suspensions: Heterogeneous mixtures with large particles that settle out (e.g., blood).

Chemical Bonds

Chemical bonds are forces that hold atoms together, forming molecules and compounds essential for life.

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions (cations and anions).

• Covalent Bonds: Formed by sharing pairs of electrons between atoms. Can be single, double, or triple bonds.

• Hydrogen Bonds: Weak attractions between polar molecules, important in water and biological macromolecules.

• Polar vs. Nonpolar Compounds:

  • Polar: Unequal electron sharing (e.g., water).

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

Chemical Reactions

Chemical reactions involve the formation, rearrangement, and breaking of bonds, driving physiological processes.

• Synthesis Reactions: Two or more substances combine to form a more complex product. General form: $A + B \rightarrow AB$

• Decomposition Reactions: A compound breaks down into simpler substances. General form: $AB \rightarrow A + B$

• Exchange (Displacement) Reactions: Involves both synthesis and decomposition. General form: $AB + CD \rightarrow AD + CB$

• Oxidation-Reduction (Redox) Reactions: Involve electron transfer; crucial for energy production.

• Reaction Rates: Influenced by temperature, concentration, particle size, and catalysts (e.g., enzymes).

Biochemistry

Inorganic Compounds

Inorganic compounds are essential for homeostasis and physiological functions.

• Water: Most abundant inorganic compound; vital for solvent action, temperature regulation, and chemical reactions.

• Salts: Important for nerve function and muscle contraction (e.g., NaCl, KCl).

• Acids and Bases:

  • Acids: Release hydrogen ions (H+); proton donors.

  • Bases: Release hydroxide ions (OH-); proton acceptors.

  • pH Scale: Measures hydrogen ion concentration; lower pH = more acidic, higher pH = more basic. pH formula: $\text{pH} = -\log_{10}[H^+]$

• Buffers: Substances that minimize changes in pH by accepting or donating H+ ions.

Organic Compounds

Organic compounds contain carbon and are synthesized and broken down by the body for various functions.

• Dehydration Synthesis: Forms organic molecules by removing water.

• Hydrolysis: Breaks down molecules by adding water.

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose, fructose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose, lactose).

• Polysaccharides: Long chains of monosaccharides (e.g., glycogen, starch).

• Function: Primary energy source for cells.

Lipids

• Building Blocks: Fatty acids and glycerol.

• Types: Triglycerides (energy storage), phospholipids (cell membranes), steroids (hormones, cholesterol).

• Functions: Energy storage, insulation, cell membrane structure.

Proteins

• Building Blocks: Amino acids (20 types).

• Levels of Structure: Primary, secondary, tertiary, quaternary.

• Functions: Structural support, transport, enzymes, communication, movement, defense.

• Enzymes: Proteins that catalyze biochemical reactions, lowering activation energy.

Nucleic Acids

• DNA (Deoxyribonucleic Acid): Stores genetic information; double helix structure.

• RNA (Ribonucleic Acid): Transmits and helps express genetic information; single-stranded.

• Nucleotides: Building blocks composed of a sugar, phosphate group, and nitrogenous base (adenine, guanine, cytosine, thymine/uracil).

ATP (Adenosine Triphosphate)

• Role: Main energy currency of the cell; transfers energy for cellular work.

• Structure: Adenine base, ribose sugar, three phosphate groups.

• Energy Release: Hydrolysis of ATP releases energy: $\text{ATP} + \text{H}_2\text{O} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

Summary Table: Major Classes of Biological Molecules

Class	Building Blocks	Main Functions	Examples
Carbohydrates	Monosaccharides	Energy source, structural support	Glucose, glycogen, starch
Lipids	Fatty acids, glycerol	Energy storage, insulation, membranes	Triglycerides, phospholipids, cholesterol
Proteins	Amino acids	Structure, enzymes, transport, signaling	Collagen, hemoglobin, enzymes
Nucleic Acids	Nucleotides	Genetic information storage and transfer	DNA, RNA

Additional info: This summary is based on the provided textbook images and expands on key concepts for clarity and completeness, suitable for college-level Anatomy & Physiology students.