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 with simple cell structure.

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

• Eukarya: Eukaryotic organisms, including 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 metabolism, growth, reproduction, response to stimuli, and homeostasis.

• Nonliving things: May have structure and mass but lack biological processes.

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 pH, and 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.

• Helps in analyzing biological processes at molecular and cellular levels.

Importance of DNA

• DNA stores genetic information essential for growth, development, and reproduction.

• Directs synthesis of proteins via transcription and translation.

Types of Chemical Bonds

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

• Covalent Bonds: Formed by sharing of electrons.

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

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.

• Radioisotopes can trace biochemical pathways.

Atoms and Charge

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

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

Element vs. Molecule

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

• Molecule: Two or more atoms bonded together.

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.

• As cell size increases, surface area grows slower than volume.

Microscopy Types

Tissues & Organ Systems

Types of Tissues and Their Functions

Types of Connective Tissues

• Loose connective tissue: Supports organs and blood vessels.

• Dense connective tissue: Forms tendons and ligaments.

• Cartilage: Provides flexible support.

• Bone: Structural support and protection.

• Blood: Transports nutrients and waste.

Muscle Type in the Stomach

• Smooth muscle: Involuntary, non-striated muscle found in the stomach and other internal organs.

Types of Junctions

• Tight junctions: Seal cells together, preventing leakage.

• Desmosomes: Provide mechanical strength.

• Gap junctions: Allow communication between cells.

Chemical Processes in Cells

Diffusion

• Movement of molecules from high to low concentration.

• Passive process, no energy required.

Plasma Membrane Structure

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

• Selective permeability regulates entry and exit of substances.

Transport Across the Plasma Membrane

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

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

Active Transport

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

• Example: Sodium-potassium pump.

Isotonic Solution

• Has equal solute concentration as the cell.

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

Cellular Respiration

Glycolysis

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

• Produces ATP and NADH.

Electron Transport Chain and ATP Production

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

Electron Carriers in Citric Acid Cycle

• NAD+ and FAD are electron carriers.

• They gain electrons from metabolic intermediates and become NADH and FADH2.

Key Equations

• Cellular respiration overall equation:

• ATP synthesis:

Example: During exercise, muscle cells increase ATP production via cellular respiration.

Additional info: Some details about electron carriers and ATP synthase were inferred for completeness.