Chemistry Basics for Anatomy & Physiology

Energy and Its Forms

Energy is the capacity to do work and is essential for all biological processes. In the human body, energy exists in several forms:

• Chemical: Stored in chemical bonds, released or absorbed during reactions.

• Electrical: Movement of charged particles, such as ions across cell membranes.

• Mechanical: Direct movement of matter, such as muscle contraction.

• Radioactive: Emission of energy from unstable atomic nuclei.

Composition of Matter

Matter is composed of elements, which are fundamental units. The human body is primarily made of:

• Carbon

• Oxygen

• Hydrogen

• Nitrogen

• Atoms are the building blocks of elements.

Subatomic Particles

Atoms consist of a nucleus and electrons:

• Protons (positive charge)

• Neutrons (neutral)

• Electrons (negative charge, orbit the nucleus)

In a neutral atom, the number of protons equals the number of electrons.

Identifying Elements

• Atomic number: Number of protons in the atom.

• Atomic mass number: Sum of protons and neutrons.

Isotopes and Atomic Weight

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

• Atomic weight: Average mass of all isotopes.

• Radioisotopes: Unstable isotopes that decompose and emit radiation.

Atoms, Bonding, and Chemical Reactions

Electrons and Bonding

Electrons occupy energy levels called electron shells. The outermost shell (valence shell) determines chemical reactivity.

• Full valence shells are stable.

• Atoms with incomplete valence shells are reactive.

Reactive Elements

• Atoms with unfilled valence shells tend to gain, lose, or share electrons to achieve stability.

Chemical Bonds

• Ionic Bonds: Electrons are transferred between atoms, forming ions (cations and anions).

• Covalent Bonds: Electrons are shared between atoms. Can be single, double, or nonpolar/polar.

Properties of Water

• Hydrogen is attracted to the negative portion of polar molecules.

• Water molecules are held together by hydrogen bonds.

Patterns of Chemical Reaction

• Synthesis reaction (): Atoms/molecules combine, energy absorbed, anabolic.

• Decomposition reaction (): Molecule broken down, energy released, catabolic.

• Exchange reaction (): Both synthesis and decomposition occur.

Biochemistry: Essentials for Life

Organic and Inorganic Compounds

• Organic compounds: Contain carbon, covalently bonded. Includes carbohydrates, lipids, proteins, nucleic acids.

• Inorganic compounds: Lack carbon. Includes water, salts, acids, bases.

Important Inorganic Compounds

• Water: Most abundant inorganic compound. Vital for heat capacity, polarity, chemical reactivity, cushioning.

• Salts: Dissociate into ions, vital for electrical gradients and cell membrane function.

• Acids and Bases: Release or accept hydrogen ions, affect pH.

pH

• Measures concentration of hydrogen ions.

• is neutral, is acidic, is basic.

• Buffers regulate pH.

Chemical Reactions in Biochemistry

• Dehydration synthesis: Monomers join to form polymers, water is removed.

• Hydrolysis: Polymers broken down into monomers, water is added.

Important Organic Compounds

Carbohydrates

• Contain carbon, hydrogen, oxygen.

• Include sugars and starches.

• Classified by size:

  • Monosaccharides: Single sugars (glucose, galactose, fructose).

  • Disaccharides: Two sugars (sucrose, maltose, lactose).

  • Polysaccharides: Long chains (cellulose, glycogen).

Lipids

• Contain carbon, hydrogen, oxygen.

• Insoluble in water.

• Include fats, oils, phospholipids, steroids.

• Saturated fats: Solid at room temperature, raise LDL cholesterol.

• Unsaturated fats: Liquid at room temperature, raise HDL cholesterol.

• Cholesterol: Steroid, component of cell membranes, precursor for hormones.

Proteins

• Account for over half of organic matter in the body.

• Contain carbon, hydrogen, oxygen, nitrogen, sometimes sulfur.

• Made of amino acids (contain amino group NH2 and acid group COOH).

• Fibrous proteins: Structural, e.g., collagen, keratin.

• Globular proteins: Functional, e.g., enzymes, antibodies.

Enzymes

• Biological catalysts, speed up reactions without being consumed.

Nucleic Acids

• Contain carbon, hydrogen, oxygen, nitrogen, phosphorus.

• Made of nucleotides (sugar, phosphate, nitrogenous base).

• DNA: Double-stranded, contains genetic information.

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

Adenosine Triphosphate (ATP)

• Primary energy carrier in cells.

• Composed of ribose, adenine, three phosphate groups.

• Energy released when phosphate bonds are broken:

Cells and Tissues

Cell Theory and Structure

• Cells are the basic structural and functional unit of life.

• All cells share general structures: nucleus, cytoplasm, plasma membrane.

The Nucleus

• Control center, contains DNA.

• Three regions:

  • Nuclear envelope: Double membrane, barrier, contains pores.

  • Nucleolus: Site of ribosome assembly.

  • Chromatin: DNA and protein, condenses to form chromosomes during cell division.

Plasma Membrane

• Barrier for cell contents.

• Double phospholipid bilayer.

Cell Junctions

• Tight junctions: Bind cells into leakproof sheets.

• Desmosomes: Anchoring junctions, prevent cells from being pulled apart.

• Gap junctions: Allow communication between cells.

Cytoplasm

• Material outside nucleus and inside plasma membrane.

• Site of most cellular activities.

• Contains:

  • Cytosol: Fluid, metabolic machinery.

  • Organelles: "Little organs" with specific functions.

  • Inclusions: Chemical substances (nutrients, cell products).

Cytoplasmic Organelles

• Mitochondria: Powerhouse, site of ATP production.

• Ribosomes: Protein synthesis, found free or on rough ER.

• Endoplasmic Reticulum (ER):

  • Rough ER: Studded with ribosomes, synthesizes proteins.

  • Smooth ER: Lipid metabolism, detoxification.

• Golgi Apparatus: Modifies, packages proteins, produces vesicles.

• Lysosomes: Contain digestive enzymes, break down waste.

• Peroxisomes: Contain oxidase enzymes, detoxify harmful substances.

• Cytoskeleton: Network of protein structures, provides cell framework.

  • Microfilaments (smallest)

  • Intermediate filaments

  • Microtubules (largest)

• Centrioles: Rod-shaped, direct formation of mitotic spindle during cell division.

Example: The mitochondria are often called the "powerhouse" of the cell because they generate ATP, which is used for energy in nearly all cellular processes.

Additional info: Some explanations and definitions have been expanded for clarity and completeness, such as the details of chemical bonds, organelle functions, and the role of ATP in cellular metabolism.