Unit 1: Basic Concepts of Anatomy & Physiology – Organization, Chemistry, and Biological Molecules

Introduction to Anatomy & Physiology

Organizational Levels of the Human Body

Understanding the human body requires knowledge of its hierarchical organization, from the smallest chemical units to the complete organism.

• Chemical Level: Atoms and molecules form the basis of all matter, including living tissue.

• Cellular Level: Cells are the basic structural and functional units of life. Examples include muscle cells and nerve cells.

• Tissue Level: Groups of similar cells performing a common function. Four basic types: epithelial, connective, muscle, and nervous tissue.

• Organ Level: Organs are structures composed of two or more tissue types working together (e.g., heart, liver).

• Organ System Level: Groups of organs that perform related functions (e.g., circulatory system).

• Organism Level: The complete living being, with all organ systems functioning together.

Example: The heart is an organ composed of muscle, connective, and nervous tissue, functioning within the cardiovascular system.

Cell Chemistry & Cell Components

Basic Chemistry: Matter and Energy

All living things are composed of matter, which occupies space and has mass. Energy is the capacity to do work and exists in various forms (chemical, electrical, mechanical, radiant).

• States of Matter: Solid, liquid, gas.

• Chemical Elements: Substances that cannot be broken down by ordinary chemical means. Examples: C, H, O, N, Ca, Na, K.

• Major Elements in the Body: Oxygen, Carbon, Hydrogen, Nitrogen.

• Minor Elements: Calcium, Sodium, Potassium, Magnesium, Sulfur, Phosphorus, Chlorine.

Example: Water (H2O) is composed of hydrogen and oxygen atoms.

Atomic Structure and Bonding

Atoms consist of subatomic particles: protons, neutrons, and electrons. The arrangement of electrons determines chemical bonding and reactivity.

• Protons: Positive charge, found in nucleus.

• Neutrons: No charge, found in nucleus.

• Electrons: Negative charge, orbit nucleus.

• Atomic Number: Number of protons in an atom.

• Bonding Sites: Hydrogen (1), Carbon (4), Oxygen (2), Nitrogen (3).

Example: Carbon forms four covalent bonds due to four available electrons in its outer shell.

Chemical Bonds

Atoms combine to form molecules through chemical bonds. The three main types are ionic, covalent, and hydrogen bonds.

• Ionic Bonds: Electrons are transferred from one atom to another, forming charged ions (e.g., NaCl).

• Covalent Bonds: Electrons are shared between atoms (e.g., H2O).

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

Example: Water molecules are held together by covalent bonds, and interact via hydrogen bonds.

Energy & Cell Processes

Chemical Reactions and Enzymes

Chemical reactions involve the making or breaking of bonds, resulting in new substances. Enzymes are biological catalysts that speed up reactions by lowering activation energy.

• Reactants: Substances entering a reaction.

• Products: Substances produced by a reaction.

• Enzyme Action: Enzymes bind substrates, catalyze reactions, and release products.

Equation:

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

Example: Digestive enzymes break down food molecules into absorbable units.

Biological Chemistry

Acids, Bases, Salts, and Electrolytes

Acids, bases, and salts are important for maintaining pH and electrolyte balance in the body.

• Acids: Release H+ ions in solution (e.g., HCl).

• Bases: Release OH- ions in solution (e.g., NaOH).

• Salts: Compounds formed from acids and bases (e.g., NaCl).

• Electrolytes: Substances that dissociate into ions and conduct electricity in solution.

Equation:

$\mathrm{H_2O \leftrightarrow H^+ (hydrogen) + OH^- (hydroxide)}$

Example: Blood pH is tightly regulated by buffers, acids, and bases.

pH and Acid-Base Balance

pH measures the concentration of hydrogen ions in solution. The scale ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

• Acidic: pH < 7

• Neutral: pH = 7

• Basic: pH > 7

• Buffers: Substances that minimize changes in pH.

Example: The bicarbonate buffer system maintains blood pH.

Biological Macromolecules

Large molecules essential for life include carbohydrates, lipids, proteins, and nucleic acids. They are built from smaller units called monomers.

• Carbohydrates: Made of C, H, O. Monosaccharides (e.g., glucose), disaccharides (e.g., sucrose), polysaccharides (e.g., starch, glycogen).

• Lipids: Include fats (triglycerides), phospholipids, and steroids. Important for energy storage and cell membranes.

• Proteins: Polymers of amino acids. Structure determines function. Four levels: primary, secondary, tertiary, quaternary.

• Nucleic Acids: DNA and RNA, composed of nucleotides (sugar, phosphate, nitrogen base).

Example: Enzymes are proteins that catalyze biochemical reactions.

Functional Groups in Biological Molecules

Functional groups are specific groups of atoms that confer unique chemical properties to molecules.

• Hydroxyl (-OH)

• Carboxyl (-COOH)

• Amino (-NH2)

• Methyl (-CH3)

Example: Amino acids contain both amino and carboxyl groups.

Hydrolysis and Dehydration Synthesis

Macromolecules are built and broken down by dehydration synthesis (removal of water to form bonds) and hydrolysis (addition of water to break bonds).

• Dehydration Synthesis: Joins monomers to form polymers.

• Hydrolysis: Breaks polymers into monomers.

Example: Digestion of starch into glucose involves hydrolysis.

Tables

Major Elements in the Human Body

Element	Symbol	Function
Oxygen	O	Component of water, needed for cellular respiration
Carbon	C	Backbone of organic molecules
Hydrogen	H	Component of water and organic molecules
Nitrogen	N	Component of proteins and nucleic acids
Calcium	Ca	Bone structure, muscle contraction
Sodium	Na	Nerve impulse transmission, fluid balance
Potassium	K	Nerve impulse transmission, muscle contraction

Types of Chemical Bonds

Bond Type	Description	Example
Ionic	Transfer of electrons, forms ions	NaCl
Covalent	Sharing of electrons	H2O
Hydrogen	Weak attraction between polar molecules	Between water molecules

Levels of Protein Structure

Level	Description
Primary	Sequence of amino acids
Secondary	Folding/coiling due to hydrogen bonding (alpha helix, beta sheet)
Tertiary	Three-dimensional folding due to side chain interactions
Quaternary	Association of multiple polypeptide chains

Summary

• The human body is organized into hierarchical levels, each with specific structure and function.

• Chemical elements and compounds form the basis of cellular structure and processes.

• Chemical bonds and reactions are essential for life, with enzymes facilitating biological processes.

• Biological macromolecules (carbohydrates, lipids, proteins, nucleic acids) are vital for structure and function.

• Acid-base balance and pH regulation are crucial for homeostasis.

Additional info: Some explanations and examples have been expanded for clarity and completeness.