Biological Chemistry in Anatomy & Physiology

This study guide covers foundational vocabulary and concepts in biological chemistry, focusing on the elements, molecules, and compounds essential for human physiology. Understanding these terms is crucial for grasping the chemical basis of life and the processes that sustain the human body.

Elements in the Human Body

Elements are pure substances consisting of only one type of atom. The human body is composed of several key elements, each playing a specific role in physiological processes.

• Major Elements: Oxygen, Carbon, Hydrogen, Nitrogen – make up over 96% of body mass.

• Mineral Elements: Sodium, Potassium, Calcium, Chlorine, Magnesium, Phosphorus, Sulfur – required in smaller amounts for various functions such as nerve conduction, muscle contraction, and bone structure.

• Trace Elements: Elements needed in minute quantities (e.g., iron, iodine, zinc) but essential for enzyme function and other processes.

Example: Calcium is vital for bone structure and muscle contraction.

Atoms and Atomic Structure

Atoms are the smallest units of matter that retain the properties of an element. Their structure determines how they interact in chemical reactions.

• Atom: Consists of a nucleus (protons and neutrons) and electron shells.

• Nucleus: Central core containing protons (positive charge) and neutrons (neutral).

• Electron Shell: Regions around the nucleus where electrons (negative charge) are found.

• Atomic Number: Number of protons in the nucleus; defines the element.

• Chemical Symbol: One- or two-letter abbreviation for an element (e.g., O for oxygen).

• Valence Shell: Outermost electron shell; determines chemical reactivity.

• Valence Electron: Electrons in the valence shell involved in bonding.

• Octet Rule: Atoms are most stable with 8 electrons in their valence shell.

• Duet Rule: Applies to very small atoms (e.g., hydrogen, helium), stable with 2 electrons.

Example: Sodium (Na) has one valence electron and tends to lose it to achieve a stable octet.

Chemical Bonds

Chemical bonds are forces that hold atoms together in molecules and compounds. The type of bond affects the properties of the resulting substance.

• Molecule: Two or more atoms chemically bonded together.

• Ionic Bond: Formed when electrons are transferred from one atom to another, creating ions (charged particles).

• Covalent Bond: Formed when atoms share electrons.

• Ion: Atom or molecule with a net electric charge.

• Cation: Positively charged ion (lost electrons).

• Anion: Negatively charged ion (gained electrons).

• Polar Covalent Bond: Unequal sharing of electrons, resulting in partial charges.

• Nonpolar Covalent Bond: Equal sharing of electrons.

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

Example: Water (H2O) molecules are held together by polar covalent bonds and form hydrogen bonds with each other.

Mixtures and Solutions

Mixtures are combinations of substances that are not chemically bonded. Solutions are a type of mixture important in physiology.

• Mixture: Physical combination of substances.

• Suspension: Large particles settle out over time (e.g., blood cells in plasma).

• Colloid: Medium-sized particles remain dispersed (e.g., cytosol).

• Solution: Homogeneous mixture of solute dissolved in solvent (e.g., salt water).

• Solute: Substance dissolved.

• Solvent: Substance doing the dissolving (usually water in the body).

• Solubility: Ability of a substance to dissolve.

• Concentration: Amount of solute in a given volume of solution.

Example: Blood plasma is a solution with water as the solvent and various solutes (glucose, ions, proteins).

Interactions with Water

Water is the universal solvent in biological systems. How substances interact with water affects their function in the body.

• Hydrophilic: Water-loving; dissolves easily in water (e.g., salts, sugars).

• Hydrophobic: Water-fearing; does not dissolve in water (e.g., fats, oils).

• Salt: Ionic compound formed from acid-base reactions; dissociates into ions in water.

• Electrolyte: Substance that conducts electricity when dissolved in water (e.g., NaCl).

Example: Sodium chloride (NaCl) is an electrolyte that dissociates into Na+ and Cl- in body fluids.

Acids, Bases, and pH

Acids and bases are important for maintaining the body's pH balance, which is crucial for enzyme function and cellular processes.

• Acid: Substance that releases hydrogen ions (H+) in solution; proton donor.

• Base: Substance that accepts hydrogen ions or releases hydroxide ions (OH-); proton acceptor.

• pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic), with 7 being neutral.

• Buffer: Substance that minimizes changes in pH by accepting or donating H+.

Example: Blood contains buffers such as bicarbonate to maintain pH around 7.4.

Formula:

Organic Compounds

Organic compounds contain carbon and are the basis of all living organisms. The four major classes are carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrate: Energy source; includes sugars and starches.

• Lipid: Fats and oils; important for energy storage, insulation, and cell membranes.

• Protein: Made of amino acids; functions include enzymes, structure, and signaling.

• Nucleic Acid: DNA and RNA; store and transmit genetic information.

• Monomer: Small building block molecule (e.g., amino acid, nucleotide).

• Polymer: Large molecule made of repeating monomers (e.g., protein, DNA).

Example: Glucose is a carbohydrate monomer; starch is a carbohydrate polymer.

Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as a primary energy source.

• Monosaccharide: Simple sugar (e.g., glucose, fructose).

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

• Polysaccharide: Many monosaccharides linked (e.g., glycogen, starch).

• Pentose: Five-carbon sugar (e.g., ribose in RNA).

• Hexose: Six-carbon sugar (e.g., glucose).

Example: Glycogen is a polysaccharide used for energy storage in animals.

Lipids

Lipids are hydrophobic molecules important for energy storage, membrane structure, and signaling.

• Fatty Acid: Long hydrocarbon chain with a carboxyl group.

• Saturated Fatty Acid: No double bonds; solid at room temperature (e.g., butter).

• Monounsaturated Fatty Acid: One double bond (e.g., olive oil).

• Polyunsaturated Fatty Acid: Two or more double bonds (e.g., fish oil).

• Glycerol: Three-carbon backbone of triglycerides.

• Triglyceride: Three fatty acids attached to glycerol; main form of stored fat.

• Phospholipid: Glycerol, two fatty acids, and a phosphate group; major component of cell membranes.

• Amphiphilic: Molecule with both hydrophilic and hydrophobic parts (e.g., phospholipids).

• Steroid: Lipid with four fused rings (e.g., cholesterol, hormones).

Example: Phospholipids form the bilayer of cell membranes.

Proteins

Proteins are polymers of amino acids and perform a vast array of functions in the body.

• Amino Acid: Building block of proteins; contains amino group, carboxyl group, and R group (side chain).

• Core: Central carbon atom of an amino acid.

• R Group: Variable side chain that determines amino acid properties.

• Peptide: Short chain of amino acids.

• Peptide Bond: Covalent bond between amino acids.

• Dipeptide: Two amino acids joined.

• Tripeptide: Three amino acids joined.

• Polypeptide: Many amino acids joined; forms proteins.

• Fibrous Protein: Long, structural (e.g., collagen).

• Globular Protein: Spherical, functional (e.g., enzymes).

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Local folding (alpha helix, beta-pleated sheet).

• Alpha Helix: Spiral shape in secondary structure.

• Beta-Pleated Sheet: Folded, sheet-like structure.

• Tertiary Structure: Overall 3D shape of a polypeptide.

• Quaternary Structure: Arrangement of multiple polypeptide chains.

Example: Hemoglobin is a globular protein with quaternary structure.

Nucleic Acids

Nucleic acids store and transmit genetic information. DNA and RNA are the two main types.

• Nucleotide: Monomer of nucleic acids; consists of a pentose sugar, phosphate group, and nitrogenous base.

• Pentose Sugar: Five-carbon sugar (ribose in RNA, deoxyribose in DNA).

• Phosphate Group: Links nucleotides together.

• Nitrogenous Base: Adenine, Guanine, Cytosine, Thymine (DNA), Uracil (RNA).

• Deoxyribonucleic Acid (DNA): Double-stranded; stores genetic information.

• Ribonucleic Acid (RNA): Single-stranded; involved in protein synthesis.

• Adenosine Diphosphate (ADP): Nucleotide with two phosphate groups; important in energy transfer.

• Adenosine Triphosphate (ATP): Nucleotide with three phosphate groups; main energy currency of the cell.

Example: ATP provides energy for cellular processes such as muscle contraction.

Summary Table: Major Classes of Biological Molecules

Additional info: This guide expands on the provided vocabulary list by grouping terms into logical categories and providing academic context, definitions, and examples to support understanding for Anatomy & Physiology students.