CH01: The Human Body

Biological Hierarchy

The biological hierarchy organizes living things from the simplest to the most complex levels. Understanding this hierarchy is crucial for grasping how the human body functions as an integrated whole.

• Levels: Chemical → Cellular → Tissue → Organ → Organ System → Organism

• Importance: Each level builds on the previous, with emergent properties at higher levels.

• Example: Muscle cells (cellular level) form muscle tissue, which makes up organs like the heart.

Life Functions and Cell Size (Surface Area/Volume Ratio)

All living organisms perform essential life functions, and most are composed of many small cells. The surface area to volume (SA/V) ratio limits cell size and efficiency.

• Key Life Functions: Metabolism, responsiveness, movement, growth, differentiation, reproduction.

• SA/V Ratio: Smaller cells have a higher SA/V ratio, allowing efficient exchange of materials.

• Example: Large cells struggle to exchange nutrients and waste efficiently.

Homeostasis

Homeostasis is the maintenance of a stable internal environment, essential for proper protein function and overall health.

• Definition: The body's ability to maintain internal conditions within narrow limits.

• Mechanisms: Negative and positive feedback loops.

• Example: Body temperature regulation.

Feedback Mechanisms

Feedback mechanisms regulate homeostasis by responding to changes in the internal environment.

• Negative Feedback: Reduces the effect of the stimulus (e.g., blood glucose regulation).

• Positive Feedback: Enhances the effect of the stimulus (e.g., blood clotting).

• Reflex Arc Components:

  1. Stimulus

  2. Receptor

  3. Control Center

  4. Effector

  5. Response

Anatomy vs. Physiology

Anatomy is the study of body structure, while physiology is the study of body function. The principle "form fits function" means that anatomical structures are shaped to perform specific physiological roles.

Organ Systems of the Human Body

The human body consists of 11 organ systems, each with distinct functions and components.

• Examples: Integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, reproductive.

• Function: Each system contributes to homeostasis and survival.

Anatomical Position and Directional Terms

The anatomical position is a standardized reference for describing body parts and directions.

• Position: Standing upright, facing forward, arms at sides, palms forward.

• Directional Terms: Anterior/posterior, superior/inferior, medial/lateral, proximal/distal, superficial/deep.

• Importance: Ensures clear communication in anatomy.

Body Planes and Sections

Body planes are imaginary lines used to divide the body for anatomical study.

• Coronal (Frontal) Plane: Divides body into anterior and posterior parts.

• Transverse Plane: Divides body into superior and inferior parts.

• Sagittal Plane: Divides body into right and left parts.

• Oblique Plane: Cuts at an angle.

Body Cavities

Body cavities protect organs and allow for organ movement and expansion.

• Posterior (Dorsal) Cavity: Cranial cavity (brain), vertebral cavity (spinal cord).

• Ventral Cavity: Thoracic cavity (pleural, mediastinum, pericardial), abdominopelvic cavity (abdominal, pelvic).

Serous Membranes

Serous membranes line the ventral body cavities and secrete serous fluid to reduce friction.

• Layers: Parietal (lines cavity wall) and visceral (covers organ).

• Types: Pericardium (heart), pleura (lungs), peritoneum (abdominopelvic organs).

CH02: Chemistry Comes Alive

Matter and Energy

Matter is anything that has mass and occupies space. Energy is the capacity to do work.

• Forms of Energy: Kinetic (motion), potential (stored).

Elements, Compounds, and Atoms

Element: Pure substance made of one type of atom. Compound: Substance formed from two or more elements chemically combined.

• Atom Structure: Protons (+), neutrons (0), electrons (-).

• Atomic Number: Number of protons.

• Atomic Mass: Number of protons + neutrons.

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

Electron Shells and the Octet Rule

Atoms are stable when their outermost shell is full (usually 8 electrons, except for the first shell which holds 2).

• Valence Electrons: Electrons in the outer shell determine chemical behavior.

• Example: Oxygen (atomic number 8): 2 electrons in first shell, 6 in second; needs 2 more to complete octet.

Chemical Bonds

Atoms form bonds to achieve stability.

• Ionic Bonds: Electrons are transferred; forms cations (+) and anions (-). Ionic bonds are often broken in water.

• Covalent Bonds: Electrons are shared between atoms. Can be nonpolar (equal sharing) or polar (unequal sharing).

• Electronegativity: Atom's tendency to attract electrons. Higher electronegativity leads to polar bonds.

• Hydrogen Bonds: Weak attractions between polar molecules (e.g., between water molecules).

Chemical Reactions and Equilibrium

Chemical reactions involve making or breaking bonds. Living systems maintain metabolic disequilibrium to drive life processes.

Water: Properties and Importance

Water is a polar molecule, forming hydrogen bonds that give rise to unique properties essential for life.

• Cohesion/Adhesion: Water molecules stick to each other and to other substances.

• High Specific Heat: Water resists temperature changes.

• Ice Floats: Solid water is less dense than liquid water.

• Solvent of Life: Dissolves many substances due to polarity.

pH, Acids, Bases, and Buffers

pH measures hydrogen ion concentration (). Acids release H+, bases accept H+, and buffers stabilize pH.

Biological Molecules

Four major classes: carbohydrates, lipids, proteins, nucleic acids.

• Carbohydrates: Monosaccharides (e.g., glucose) form polysaccharides (e.g., starch, glycogen, cellulose).

• Lipids: Not polymers. Include fats (triglycerides), phospholipids, steroids. Saturated fats have no double bonds; unsaturated have one or more.

• Proteins: Made of 20 amino acids. Structure levels: primary, secondary, tertiary, quaternary. Denaturation disrupts function.

• Nucleic Acids: DNA and RNA. Nucleotides consist of a sugar, phosphate, and nitrogenous base. Central Dogma: DNA → RNA → Protein.

Enzymes and Reactions

Enzymes catalyze reactions. Dehydration synthesis builds polymers; hydrolysis breaks them down.

ATP: The Energy Currency

Adenosine triphosphate (ATP) stores and transfers energy in cells.

• Why ATP? Universal, efficient, and easily regenerated.

CH03: Cells

Energy and Electronegativity

Energy is the capacity to do work. Electrons moving from less to more electronegative atoms (e.g., hydrogen to oxygen) release energy.

Aerobic Cellular Respiration

Cells extract energy from glucose in four main steps:

1. Glycolysis: Glucose → pyruvate (in cytoplasm).

2. Pyruvate Oxidation: Pyruvate → Acetyl-CoA (in mitochondria).

3. Citric Acid (Krebs) Cycle: Acetyl-CoA → CO2 + high-energy electrons.

4. Oxidative Phosphorylation: Electron transport chain and chemiosmosis produce ATP.

• Electron Transport Chain: Electrons "fall" to oxygen, releasing energy to pump protons.

• Chemiosmosis: ATP synthase uses proton flow to make ATP.

Fermentation

Fermentation allows ATP production without oxygen, producing lactic acid or ethanol as byproducts.

Alternative Energy Sources

Fats and proteins can also be used for cellular respiration when glucose is scarce.

Cell Types: Prokaryotes vs. Eukaryotes

Prokaryotes: No nucleus or membrane-bound organelles (e.g., bacteria). Eukaryotes: Have nucleus and organelles (e.g., human cells).

• Importance of Membranes: Compartmentalization allows specialized functions.

Cell Size and SA/V Ratio

Cells remain small to maximize surface area relative to volume, ensuring efficient exchange of materials.

Cell Structure and Function

Each cell part (organelle) has a specific structure and function. Additional info: Common organelles include nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and cytoskeleton.

Plasma Membrane Structure

The plasma membrane is a phospholipid bilayer with embedded proteins, making it selectively permeable.

• Phospholipid Arrangement: Hydrophilic heads face outward; hydrophobic tails face inward.

• Selectively Permeable: Allows some substances to pass more easily than others.

Membrane Transport

• Passive Transport: No energy required; substances move down concentration gradient.

  • Simple Diffusion: Direct movement through membrane.

  • Osmosis: Diffusion of water.

  • Tonicity: Effect of solution on cell volume.

    • Isotonic: No net water movement; cell stable.

    • Hypertonic: Water leaves cell; cell shrivels.

    • Hypotonic: Water enters cell; cell may burst.

  • Facilitated Diffusion: Uses transport proteins (channels or carriers).

• Active Transport: Requires energy (usually ATP); moves substances against gradient.

  • Example: Sodium-potassium pump.

• Bulk Transport: Movement of large particles via endocytosis (into cell) or exocytosis (out of cell).