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 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 ranges from simple to complex structures.

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

Shared Characteristics of Living and Nonliving Things

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

• 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 pH, 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 Chemical Bonds

• Ionic Bonds: Transfer of electrons between atoms, forming charged ions.

• Covalent Bonds: Sharing of electrons between atoms.

• Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom (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.

Atoms and Charge

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

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

Elements vs. Molecules

• 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

• Nucleus: Stores DNA; spherical.

• Mitochondria: Produces ATP; oval-shaped.

• Ribosomes: Protein synthesis; small, round.

• Endoplasmic Reticulum (ER): Synthesis and transport; network of membranes.

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

• Lysosomes: Digestion; spherical vesicles.

• Plasma Membrane: Controls entry/exit; flexible boundary.

Cell Size and Surface Area

Cell efficiency depends on the ratio of surface area to volume.

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

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 movement of molecules from high to low concentration.

• Occurs across cell membranes for gases and small molecules.

Plasma Membrane Structure

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

Transport Across the Plasma Membrane

• Passive Transport: No energy required (diffusion, osmosis).

• Active Transport: Requires energy (ATP) to move substances against concentration gradient.

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

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

Isotonic Solutions

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

• Cells retain their shape in isotonic solutions.

Cellular Respiration

Glycolysis

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

• Produces ATP and NADH.

Electron Transport Chain

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

Citric Acid Cycle (Krebs Cycle)

• Electron carriers: NAD+ and FAD collect electrons from metabolic reactions.

• Electrons are transferred 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 impulses.

Types of Connective Tissues

• Loose Connective Tissue: Cushions organs.

• Dense Connective Tissue: Provides strength (e.g., tendons).

• Cartilage: Flexible support.

• Bone: Rigid support.

• Blood: Transport of substances.

Location of Tissues

• 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: Found in the stomach; involuntary contractions for digestion.

Types of Junctions

• Tight Junctions: Seal cells together, prevent leakage.

• Desmosomes: Anchor cells together.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Tissues and Their Functions

Summary Table: Types of Cell Junctions

Key Equations

• Surface Area to Volume Ratio:

• pH Calculation:

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