Introduction to Biology

Domains of Life

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

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

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.

Characteristics of Living vs. Nonliving Things

• Living: Cellular organization, metabolism, growth, reproduction, response to stimuli, adaptation.

• Nonliving: Lack of cellular structure, metabolism, and reproduction.

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 function by analyzing individual organelles.

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

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.

Atomic Charge Changes

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

Interaction of Charged Elements

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

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Stores DNA; spherical shape.

• Mitochondria: Site of ATP production; oval shape.

• Ribosomes: Protein synthesis; small, round particles.

• Endoplasmic Reticulum (ER): Synthesis of proteins (rough ER) and lipids (smooth ER); network of tubules.

• Golgi Apparatus: Modifies, sorts, 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 Relationship

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

• Formula: for a cube

Microscopy Types and Uses

• Light Microscopy: Observes living cells and tissues.

• Electron Microscopy: High-resolution imaging of cell structures.

• Fluorescence Microscopy: Visualizes specific molecules using fluorescent tags.

Diffusion

• Movement of molecules from high to low concentration.

• Example: Oxygen diffusing into cells.

Plasma Membrane Structure

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

Plasma Membrane Permeability

• 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 Solutions

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

• Cells retain their normal shape.

ATP Production in Electron Transport Chain

• Most ATP is produced by the ATP synthase protein complex.

Glycolysis Purpose

• Breaks down glucose into pyruvate, producing ATP and NADH.

Electron Carriers in Citric Acid Cycle

• NAD+ and FAD collect electrons from metabolic reactions.

• Electrons are transferred to the electron transport chain.

Tissues & Organ Systems

Types of Connective Tissues

• Loose Connective Tissue: Supports and binds other tissues.

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

• Adipose Tissue: Stores fat.

• Cartilage: Flexible support.

• Bone: Rigid support.

• Blood: Transport of substances.

Locations of Tissue Types

• Epithelial Tissue: Covers body surfaces, lines organs.

• Connective Tissue: Found throughout the body (e.g., under skin, in bones).

• Muscle Tissue: Skeletal (attached to bones), cardiac (heart), smooth (walls of organs).

• Nervous Tissue: Brain, spinal cord, nerves.

Muscle Type in the Stomach

• Smooth Muscle: Involuntary, found in the walls of the stomach and other organs.

Types of Tissues and Their Functions

• Epithelial: Protection, absorption, secretion.

• Connective: Support, transport, storage.

• Muscle: Movement.

• Nervous: Communication, control.

Types of Junctions

• Tight Junctions: Seal cells together, prevent leakage.

• Desmosomes: Anchor cells, provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Additional info: Academic context and definitions were added to expand brief review points into full explanations. Table was inferred for tissue types, locations, and functions.