Biochemical Processes and Biological Molecules: Foundations for Anatomy & Physiology

Biochemical Processes and Biological Molecules

Introduction

Understanding biochemical processes and biological molecules is essential for the study of Anatomy & Physiology. These concepts form the basis for cellular structure, function, and the chemical reactions that sustain life.

Matter and Energy

Definition and Properties of Matter

• Matter: Anything that occupies space and has mass (weight).

• Matter can undergo physical changes (basic nature is not altered) or chemical changes (composition changes).

Forms of Energy

• Energy: The ability to do work; does not occupy space or have mass.

• Types of energy relevant to biological systems:

  • Chemical energy: Stored in chemical bonds; released during chemical reactions.

  • Electrical energy: Movement of charged particles (ions); important in nerve impulses.

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

  • Radiant energy: Energy that travels in waves (e.g., light, UV radiation).

• Kinetic energy: Energy of motion.

• Potential energy: Stored energy.

Example: Muscle contraction uses mechanical energy, which is derived from chemical energy stored in ATP.

Physical States of Matter

States and Examples

• Solid: Definite shape and volume (e.g., bones).

• Liquid: Definite volume, no definite shape (e.g., blood).

• Gas: No definite shape or volume (e.g., air in lungs).

Transitions between states (e.g., evaporation, condensation) involve energy absorption or release.

Elements and Atomic Structure

Elements in the Human Body

• Four major elements: Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N).

• Trace elements (e.g., Silicon, Fluorine, Copper) are present in small amounts and have specialized functions.

Atomic Structure

• Atoms: Fundamental units of matter, composed of protons, neutrons, and electrons.

• Nucleus: Contains protons (+) and neutrons (neutral).

• Electrons: Negatively charged, orbit the nucleus.

Atomic Number and Mass

• Atomic number: Number of protons in the nucleus.

• Atomic mass: Sum of protons and neutrons.

Isotopes and Radioactivity

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

• Radioisotopes: Unstable isotopes that decay, releasing energy (radioactivity).

• Applications: Used as tracers in medical imaging (e.g., CT, PET scans).

Chemical Reactions in the Body

Types of Chemical Reactions

• Synthesis reactions ($A + B \rightarrow AB$): Atoms or molecules combine; energy is absorbed. Basis for anabolic activities.

• Decomposition reactions ($AB \rightarrow A + B$): Molecule is broken down; energy is released. Basis for catabolic activities.

Inorganic and Organic Compounds

Inorganic Compounds

• Do not contain carbon (except CO2 and CO).

• Examples: Water, Salts, Acids, Bases.

Organic Compounds

• Contain carbon; often large and complex.

• Examples: Carbohydrates, Lipids, Proteins, Nucleic acids.

Water: Properties and Functions

Unique Properties

• High heat capacity: Absorbs and releases heat slowly.

• Universal solvent: Dissolves many substances, facilitating transport and chemical reactions.

• Chemical reactivity: Participates in hydrolysis and dehydration synthesis reactions.

• Cushioning: Protects organs (e.g., cerebrospinal fluid, amniotic fluid).

Salts and Electrolytes

Role in the Body

• Salts: Ionic compounds; dissociate in water to form electrolytes.

• Electrolytes: Conduct electrical currents; essential for nerve and muscle function, acid-base balance, and fluid balance.

• Major ions: Sodium (Na+), Potassium (K+), Calcium (Ca2+), Phosphorus (P).

Electrolyte Locations

• Intracellular fluid: High K+, low Na+.

• Extracellular fluid: High Na+, low K+.

• Blood: Electrolyte balance maintained by kidneys.

Acids, Bases, and pH

Definitions

• Acids: Proton donors; release H+ ions in solution.

• Bases: Proton acceptors; release OH- ions in solution.

pH Scale

• Measures concentration of H+ ions.

• Scale: 0 (most acidic) to 14 (most basic); 7 is neutral.

• Normal blood pH: 7.35–7.45 (slightly alkaline).

Buffer Systems

• Maintain pH homeostasis via buffers, respiration, and kidney excretion.

Carbohydrates

Structure and Function

• Composed of carbon, hydrogen, and oxygen (C:H:O ratio ~1:2:1).

• Primary function: Energy source for cells.

• Types:

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

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

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

Example: Glycogen is the storage form of glucose in animals.

Lipids

Structure and Types

• Hydrophobic molecules; mostly carbon and hydrogen.

• Functions: Energy storage, membrane structure, insulation.

• Types:

  • Triglycerides: Major energy storage form.

  • Phospholipids: Major component of cell membranes.

  • Steroids: Hormones (e.g., estrogen, testosterone), cholesterol.

  • Fat-soluble vitamins: Vitamins A, D, E, K.

  • Lipoproteins: Transport lipids in blood (HDL, LDL).

Saturated vs Unsaturated Fats

• Saturated fats: No double bonds; solid at room temperature (e.g., animal fats).

• Unsaturated fats: One or more double bonds; liquid at room temperature (e.g., plant oils, fish oils).

Example: Olive oil is rich in monounsaturated fats, which are considered heart-healthy.

Proteins

Structure and Function

• Composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

• Building blocks: Amino acids (20 types).

• Functions:

  • Structural (e.g., collagen, keratin)

  • Contractile (e.g., actin, myosin)

  • Transport (e.g., hemoglobin)

  • Enzymatic (e.g., digestive enzymes)

  • Hormonal (e.g., insulin, growth hormone)

  • Immunological (e.g., antibodies)

Peptide Bonds and Protein Structure

• Amino acids are linked by peptide bonds via condensation (dehydration synthesis).

Enzymes

• Biological catalysts; speed up chemical reactions by lowering activation energy.

• Not consumed in the reaction.

• Specificity: Each enzyme acts on a particular substrate at its active site.

Example: Amylase is an enzyme that catalyzes the breakdown of starch into sugars.

Nucleic Acids

Structure and Function

• Composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

• Types:

  • DNA (Deoxyribonucleic Acid): Stores genetic information; directs protein synthesis.

  • RNA (Ribonucleic Acid): Involved in protein synthesis and gene regulation.

• Building blocks: Nucleotides (composed of a sugar, phosphate group, and nitrogenous base).

Example: DNA determines inherited characteristics and controls cellular activities.

Energy Compounds: ATP

ATP Structure and Function

• Adenosine Triphosphate (ATP): The primary energy carrier in cells.

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

• Energy is released when ATP is hydrolyzed to ADP (adenosine diphosphate) and inorganic phosphate.

Equation:

$\text{ATP} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

ATP is produced during cellular respiration and used for all cellular work.

Summary Table: Principal Elements in the Human Body

Element	% of Total Body Weight	Significance
Oxygen (O)	65.0%	Essential for oxidation of glucose to produce ATP
Carbon (C)	18.5%	Primary element in all organic molecules
Hydrogen (H)	9.5%	Influences pH as an ion
Nitrogen (N)	3.2%	Component of proteins and nucleic acids
Calcium (Ca)	1.5%	Bone health, muscle contraction, nerve function
Phosphorus (P)	1.0%	Component of nucleic acids, ATP, bone
Potassium (K)	0.4%	Nerve impulses, muscle contraction
Sulfur (S)	0.3%	Component of proteins
Sodium (Na)	0.2%	Fluid balance, nerve impulses
Chlorine (Cl)	0.2%	Fluid balance
Magnesium (Mg)	0.1%	Enzyme cofactor
Iodine (I)	0.1%	Thyroid hormone synthesis
Iron (Fe)	0.1%	Hemoglobin, oxygen transport

Additional info: Some content was expanded for clarity and completeness, including definitions, examples, and academic context for key terms and processes.