Introduction to Biology

Domains of Life

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

• Bacteria: Prokaryotic, unicellular organisms lacking a nucleus.

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

• Eukarya: Eukaryotic organisms with 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: Exhibit organization, metabolism, responsiveness, growth, development, reproduction, and homeostasis.

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

• Examples: Regulation of body temperature, blood glucose levels.

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, directs protein synthesis, and enables inheritance.

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 partially charged atoms, important in water and DNA structure.

Polarity

• 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.

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

Cell organelles perform specialized functions within eukaryotic cells.

Cell Size and Surface Area

• Smaller cells have a higher surface area-to-volume ratio, facilitating efficient exchange of materials.

• Formula: for a cube

Microscopy Types

Element vs. Molecule

• Element: Pure substance made of one type of atom (e.g., O2).

• Molecule: Two or more atoms bonded together (e.g., H2O).

Cell Membrane & Transport

Plasma Membrane Structure

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

• Functions: Selective permeability, cell signaling, protection.

Diffusion

• Movement of molecules from high to low concentration.

• Passive process, no energy required.

Active Transport

• Movement of substances against concentration gradient using energy (ATP).

• Example: Sodium-potassium pump.

What Can and Can't Pass Through the Plasma Membrane

• Can pass: Small, nonpolar molecules (e.g., O2, CO2), some small polar molecules (e.g., H2O).

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

Isotonic Solution

• Has equal solute concentration as the cell.

• Cells retain their shape; no net movement of water.

Cellular Respiration & Metabolism

Glycolysis

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

• Produces ATP and NADH.

Electron Transport Chain & ATP Production

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

• Electron carriers (NADH, FADH2) donate electrons.

Citric Acid Cycle Electron Carriers

• NAD+ and FAD collect electrons during the cycle, becoming NADH and FADH2.

Tissues & Organ Systems

Types of Connective Tissues

Types of Tissues and Their Functions

• Epithelial: Covers surfaces, lines cavities, protection, absorption.

• Connective: Supports, binds, protects organs.

• Muscle: Movement; includes skeletal, cardiac, and smooth muscle.

• Nervous: Transmits electrical signals, communication.

Location of Each Tissue Type

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, ligaments, blood, bone.

• Muscle: Skeletal muscles, heart (cardiac), stomach (smooth).

• Nervous: Brain, spinal cord, nerves.

Type of Muscle in the Stomach

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

Types of Junctions

• Tight junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap junctions: Allow communication between cells.

Example: Tight junctions in intestinal lining prevent leakage of digestive enzymes.