Introduction to Biology

Domains of Life

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

• Bacteria: Prokaryotic, unicellular organisms lacking a nucleus.

• Archaea: Prokaryotic, unicellular, 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

Shared Characteristics of Living and Nonliving Things

• Living things: Composed of cells, capable of growth, reproduction, response to stimuli, metabolism, and homeostasis.

• Nonliving things: May have structure and organization but lack cellular processes and metabolism.

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).

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 essential for cell survival.

• Nucleus: Stores DNA; round, central structure.

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

• Ribosomes: Protein synthesis; small, spherical.

• Endoplasmic Reticulum (ER): Protein and lipid synthesis; network of membranes.

• 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.

• Chloroplasts: Photosynthesis (plants); oval with internal stacks.

Cell Size and Surface Area

Cell size affects surface area-to-volume ratio, influencing transport efficiency.

• Smaller cells have higher surface area relative to volume, allowing efficient exchange.

Microscopy Types

• Light Microscopy: Observes living cells, basic structure.

• Electron Microscopy: High resolution, detailed internal structures.

• Fluorescence Microscopy: Visualizes specific molecules using fluorescent tags.

Diffusion

Diffusion is the passive movement of molecules from high to low concentration.

• Important for gas exchange and nutrient transport.

Plasma Membrane Structure

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

Transport Across Plasma Membrane

• Can Pass: Small, nonpolar molecules (e.g., O2, CO2).

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

Active Transport

Active transport moves substances against concentration gradients using energy (ATP).

• Example: Sodium-potassium pump.

Isotonic Solutions

An isotonic solution has equal solute concentration as the cell, causing no net water movement.

• Cells retain normal shape in isotonic solutions.

Glycolysis

Glycolysis is the first step in cellular respiration, breaking down glucose to produce ATP.

• Occurs in cytoplasm; produces pyruvate, ATP, and NADH.

Electron Transport Chain & ATP Production

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

Electron Carriers in Citric Acid Cycle

• NAD+ and FAD are electron carriers; they gain electrons from metabolic reactions.

Tissues & Organ Systems

Types of Tissues and Their Functions

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

• Connective Tissue: Supports, binds, and protects; includes bone, blood, cartilage.

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

• Nervous Tissue: Communication; neurons and supporting cells.

Types of Connective Tissues

• Loose Connective Tissue: Cushions organs.

• Dense Connective Tissue: Tendons and ligaments.

• Cartilage: Flexible support.

• Bone: Rigid support.

• Blood: Transport of substances.

Location of Each Tissue Type

• Epithelial: Skin, lining of digestive tract.

• Connective: Bone, blood, tendons.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Type of Muscle in the Stomach

• Smooth Muscle: Involuntary, non-striated; found in stomach walls.

Types of Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Cell Junctions

Summary Table: Types of Tissues

Key Equations

• Surface Area to Volume Ratio:

• Diffusion Rate (Fick's Law): Where: D = diffusion coefficient, \(\Delta C\) = concentration difference, \(\Delta x\) = distance

• ATP Production (Cellular Respiration):

Additional info: Academic context and definitions were expanded for clarity and completeness. Tables were inferred and constructed for tissue and junction types based on standard biology knowledge.