Basic Chemistry and Biochemistry for Anatomy & Physiology

Part 1: Basic Chemistry

2.1 Matter and Energy

Understanding the nature of matter and energy is fundamental to the study of Anatomy & Physiology, as all biological processes are governed by chemical and physical principles.

• Matter: Anything that has mass and occupies space. Examples include solids, liquids, and gases.

• Energy: The capacity to do work or cause change. Energy exists in various forms, such as chemical, electrical, mechanical, and radiant energy.

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

• Kinetic Energy: Energy of motion.

• Major Energy Forms: Chemical (stored in bonds), electrical (movement of charged particles), mechanical (movement of matter), and radiant (energy traveling in waves).

• Example: Muscle contraction converts chemical energy (from ATP) into mechanical energy.

2.2 Atomic Structure and Elements

The properties of elements depend on the structure of their atoms, which are the basic units of matter.

• Chemical Element: A pure substance consisting of only one type of atom. Four elements (carbon, hydrogen, oxygen, nitrogen) make up most of the human body.

• Subatomic Particles: Protons (positive charge, mass ~1 amu), Neutrons (no charge, mass ~1 amu), Electrons (negative charge, negligible mass).

• Atomic Number: Number of protons in the nucleus.

• Atomic Mass: Sum of protons and neutrons.

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

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

• Radioisotope: Isotope with an unstable nucleus that emits radiation.

• Example: Carbon-12 and Carbon-14 are isotopes of carbon.

2.3 Molecules, Compounds, and Mixtures

Atoms bond to form molecules, which can combine to make compounds or mixtures.

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

• Compound: Molecule containing two or more different elements (e.g., H2O).

• Mixture: Physical combination of substances without chemical bonding.

• Types of Mixtures:

  • Solution: Homogeneous mixture (e.g., salt water).

  • Colloid: Heterogeneous mixture with larger particles (e.g., cytoplasm).

  • Suspension: Mixture with visible particles that settle (e.g., blood cells in plasma).

2.4 Chemical Bonds: Ionic, Covalent, and Hydrogen

Chemical bonds hold atoms together in molecules and compounds, influencing their properties and functions.

• Ionic Bond: Transfer of electrons from one atom to another, forming charged ions (e.g., NaCl).

• Covalent Bond: Sharing of electrons between atoms (e.g., H2O).

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., between water molecules).

• Octet Rule: Atoms tend to gain, lose, or share electrons to achieve eight electrons in their outer shell.

• Polar vs. Nonpolar Compounds: Polar compounds have unequal sharing of electrons; nonpolar compounds share electrons equally.

• Comparison Table:

Bond Type	Electron Movement	Strength	Example
Ionic	Transferred	Strong (in solid)	NaCl
Covalent	Shared	Strong	H2O
Hydrogen	Attraction	Weak	Between H2O molecules

2.5 Chemical Reactions

Chemical reactions involve the making or breaking of bonds, resulting in new substances.

• Major Types:

  • Synthesis: Building larger molecules from smaller ones ($A + B \rightarrow AB$).

  • Decomposition: Breaking down molecules ($AB \rightarrow A + B$).

  • Exchange: Rearranging parts of molecules ($AB + CD \rightarrow AC + BD$).

• Oxidation-Reduction (Redox) Reactions: Transfer of electrons between molecules; important in metabolism.

• Reversibility: Many reactions in the body are reversible, but some proceed mainly in one direction due to physiological conditions.

• Factors Affecting Reaction Rates: Temperature, concentration, particle size, and catalysts (enzymes).

Part 2: Biochemistry

2.6 Inorganic Compounds: Water, Salts, Acids, and Bases

Inorganic compounds are essential for life, providing structure and participating in chemical reactions.

• Water: Most abundant compound in the body; solvent, temperature regulator, and reactant.

• Salts: Ionic compounds that dissociate in water; important for nerve and muscle function.

• Acids: Release hydrogen ions ($H^+$) in solution; proton donors.

• Bases: Accept hydrogen ions; proton acceptors.

• pH Concept: Measure of hydrogen ion concentration; scale from 0 (acidic) to 14 (basic). Neutral pH is 7.

• Example: Blood pH is tightly regulated around 7.4.

2.7 Organic Compounds: Dehydration Synthesis and Hydrolysis

Organic molecules are formed and broken down by specific chemical reactions.

• Dehydration Synthesis: Removal of water to join monomers into polymers.

• Hydrolysis: Addition of water to break polymers into monomers.

• Example: Formation and breakdown of proteins, carbohydrates, and nucleic acids.

2.8 Carbohydrates

Carbohydrates are the body's primary source of energy and have structural roles.

• Building Blocks: Monosaccharides (simple sugars, e.g., glucose).

• General Structure: Carbon, hydrogen, and oxygen in a 1:2:1 ratio.

• Biological Function: Energy source, cell recognition, and structural support.

• Significance: Glucose is the main fuel for cellular respiration.

2.9 Lipids

Lipids insulate organs, build cell membranes, and store energy.

• Building Blocks: Fatty acids and glycerol.

• General Structure: Hydrophobic molecules, mostly carbon and hydrogen.

• Biological Functions: Energy storage, insulation, protection, and membrane structure.

• Classes of Lipids:

  • Triglycerides: Energy storage.

  • Phospholipids: Major component of cell membranes.

  • Steroids: Hormones and membrane structure (e.g., cholesterol).

  • Eicosanoids: Signaling molecules (e.g., prostaglandins).

2.10 Proteins

Proteins are essential structural and functional molecules in the body.

• Levels of Protein Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helices and beta sheets formed by hydrogen bonding.

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

  • Quaternary: Association of multiple polypeptide chains.

• Enzymes: Biological catalysts that speed up chemical reactions without being consumed.

• Enzyme Action: Lower activation energy, increase reaction rate, and are specific to substrates.

• Example: Amylase breaks down starch into sugars.

2.11 Nucleic Acids: DNA and RNA

Nucleic acids store and transmit genetic information, essential for cell function and inheritance.

• Classes: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

• Monomers: Nucleotides, each composed of a sugar, phosphate group, and nitrogenous base.

• Polymers: Large macromolecules made of repeating nucleotide units.

• Significance: DNA stores genetic code; RNA is involved in protein synthesis.

2.12 ATP: The Universal Energy Currency

ATP (adenosine triphosphate) is the primary energy carrier in cells, fueling most cellular processes.

• Role in Metabolism: Transfers energy from catabolic reactions to cellular work.

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

• Energy Release: Hydrolysis of ATP to ADP releases energy ($ATP \rightarrow ADP + P_i + \text{energy}$).

• Universal Energy Currency: Used by all cells for processes such as muscle contraction, active transport, and biosynthesis.