Introduction to Biology

Domains of Life

The domain system classifies all living organisms into three major groups based on cellular organization and genetic differences.

• Bacteria: Prokaryotic, unicellular organisms lacking a nucleus.

• Archaea: Prokaryotic, unicellular, often found in extreme environments; genetically distinct from bacteria.

• Eukarya: Eukaryotic organisms with cells containing a nucleus; includes animals, plants, fungi, and protists.

Hierarchy of Living Organisms

Biological organization follows a hierarchical structure from smallest to largest.

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organism

Shared Characteristics of Living and Nonliving Things

• Living things: Organization, metabolism, responsiveness, growth, development, reproduction, homeostasis.

• Nonliving things: May have structure but lack metabolism, growth, and reproduction.

Scientific Method

The scientific method is a systematic approach to investigation.

• Observation

• Hypothesis

• Experiment

• Data Collection

• Analysis

• Conclusion

Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes.

• Example: Regulation of body temperature.

Chemistry of Life

Most Abundant Elements in Humanity

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

• Phosphorus (P)

• Sulfur (S)

Reductionism

Reductionism is the approach of understanding complex systems by studying their simpler components.

Importance of DNA

• DNA stores genetic information, directs protein synthesis, and enables inheritance.

Types of Chemical Bonds

• Ionic Bonds: Formed by transfer of electrons between atoms.

• Covalent Bonds: Formed by sharing electrons between atoms.

• Hydrogen Bonds: Weak attractions between partially charged atoms, important in water and DNA structure.

Polarity of Molecules

• Polar molecules: Unequal sharing of electrons, resulting in partial charges (e.g., water).

• Nonpolar molecules: Equal sharing of electrons, no charge separation (e.g., methane).

Acids, Bases, and pH

• Acidic: pH < 7

• Basic (Alkaline): pH > 7

• Neutral: pH = 7

Elements vs. Molecules

• Element: Pure substance consisting of one type of atom.

• Molecule: Two or more atoms bonded together.

Radioisotope Technology

• Used in medical imaging, cancer treatment, and biological research.

Changing Atomic Charges

• Atoms gain or lose electrons to become ions (charged particles).

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Stores DNA; round, central structure.

• Mitochondria: Produces ATP; oval with inner folds (cristae).

• Ribosomes: Protein synthesis; small, spherical.

• Endoplasmic Reticulum (ER): Synthesis and transport; rough (with ribosomes) or smooth (without).

• Golgi Apparatus: Modifies and packages proteins; stack of flattened sacs.

• Lysosomes: Digests waste; spherical vesicles.

• Plasma Membrane: Controls entry/exit; flexible, thin layer.

Cell Size and Surface Area

Cell size is limited by surface area-to-volume ratio, affecting nutrient and waste exchange.

• Smaller cells have higher surface area relative to volume, allowing efficient transport.

Microscopy Types

• Light Microscopy: Used for viewing live cells and tissues.

• Electron Microscopy: Used for high-resolution images of cell structures.

Diffusion

Diffusion is the passive movement of molecules from high to low concentration.

• Example: Oxygen moving into cells.

Plasma Membrane Structure

• Composed of phospholipid bilayer, proteins, cholesterol, and carbohydrates.

Transport Across the Plasma Membrane

• Can pass: Small, nonpolar molecules (e.g., O2, CO2).

• Cannot pass: Large, polar molecules and ions without transport proteins.

Active Transport

Active transport moves substances against their concentration gradient using energy (ATP).

• Example: Sodium-potassium pump.

Isotonic Solutions

An isotonic solution has equal solute concentration as the cell, causing no net water movement.

• Cells retain their shape in isotonic solutions.

ATP Production: Electron Transport Chain

• Most ATP is produced by the ATP synthase protein complex during the electron transport chain.

Glycolysis

Glycolysis is the first step in cellular respiration, breaking down glucose to produce ATP.

• Occurs in the cytoplasm.

• Produces pyruvate, ATP, and NADH.

Electron Carriers in Citric Acid Cycle

• NAD+ and FAD are electron carriers.

• They gain electrons from metabolic reactions and transfer them to the electron transport chain.

Tissues & Organ Systems

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces, lines cavities, protects, absorbs, and secretes.

• Connective Tissue: Supports, binds, and protects organs.

• Muscle Tissue: Contracts to produce movement.

• Nervous Tissue: Transmits electrical signals.

Types of Connective Tissues

• Loose Connective Tissue: Cushions organs.

• Dense Connective Tissue: Forms tendons and ligaments.

• Cartilage: Provides flexible support.

• Bone: Provides rigid support.

• Blood: Transports substances.

Location of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, ligaments, bone, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Muscle Type in the Stomach

• Smooth muscle is found in the stomach, enabling involuntary contractions.

Types of Junctions

• Tight Junctions: Seal cells together, preventing leakage.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Tissues and Their Functions

Summary Table: Cell Organelles

Summary Table: Types of Chemical Bonds

Key Equations

• Surface Area to Volume Ratio:

• ATP Production (Cellular Respiration):

• pH Calculation:

Additional info: Academic context was added to clarify and expand brief review points, ensuring completeness and self-contained explanations for exam preparation.