Introduction to Biology

Domains of Life

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

• Bacteria: Prokaryotic, unicellular organisms lacking a nucleus.

• Archaea: Prokaryotic, 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 → Cells → Tissues → Organs → Organ Systems → Organism

Shared Characteristics of Living and Nonliving Things

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

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

Scientific Method

The scientific method is a systematic approach to investigation.

1. Observation

2. Hypothesis

3. Experiment

4. Data Collection

5. Analysis

6. 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.

• Example: Studying cell organelles to understand cell function.

Importance of DNA

• DNA stores genetic information and directs cellular activities.

• Essential for inheritance, protein synthesis, and cell division.

Types of Bonds

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

• Covalent Bonds: Formed by sharing electrons between atoms.

• Hydrogen Bonds: Weak attractions between hydrogen and electronegative atoms (e.g., oxygen).

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

Radioisotope Technology

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

• Example: PET scans use radioisotopes to visualize metabolic activity.

Atoms and Charge

• Atoms change charge by gaining or losing electrons, forming ions.

• Negatively charged elements (anions) attract positively charged elements (cations).

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Stores DNA; round, central structure.

• Mitochondria: Site of ATP production; oval with inner folds (cristae).

• Ribosomes: Protein synthesis; small, spherical.

• Endoplasmic Reticulum (ER): Synthesis and transport; rough (with ribosomes) or smooth.

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

• Lysosomes: Digestion of cellular waste; spherical vesicles.

• Plasma Membrane: Controls entry/exit; flexible, phospholipid bilayer.

Cell Size and Surface Area

Cell size is limited by the 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.

• Fluorescence Microscopy: Used to visualize specific molecules with fluorescent tags.

Plasma Membrane Structure

• Composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

Transport Across the Plasma Membrane

• Diffusion: Passive movement of molecules from high to low concentration.

• Active Transport: Movement against concentration gradient, requires energy (ATP).

• Selective Permeability: Small, nonpolar molecules pass easily; large or charged molecules require transport proteins.

Isotonic Solutions

• Isotonic: Equal solute concentration inside and outside the cell; no net water movement.

• Cells retain normal shape in isotonic solutions.

Cellular Metabolism

Glycolysis

• First step in cellular respiration; breaks down glucose into pyruvate.

• Produces ATP and NADH.

Electron Transport Chain (ETC)

• Most ATP is produced in the ATP synthase protein complex during ETC.

Citric Acid Cycle (Krebs Cycle)

• Electron carriers NADH and FADH2 are produced.

• They receive electrons from metabolic intermediates.

Tissues & Organ Systems

Types of Tissues and Their Functions

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

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

• Muscle Tissue: Contracts to produce movement.

• Nervous Tissue: Transmits electrical impulses.

Types of Connective Tissues

• Loose Connective Tissue: Cushions organs.

• Dense Connective Tissue: Forms tendons and ligaments.

• Cartilage: Provides flexible support.

• Bone: Structural support.

• Blood: Transports substances.

Locations 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: Involuntary, non-striated muscle found in the stomach wall.

Types of Junctions

• Tight Junctions: Seal cells together, prevent leakage.

• Desmosomes: Anchor cells, provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Tissues and Their Functions

Summary Table: Cell Organelles

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 into full explanations, tables, and equations for exam preparation.