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.

• Archaea: Prokaryotic, often found in extreme environments.

• Eukarya: Eukaryotic, includes plants, animals, fungi, and protists.

Hierarchy of Living Organisms

Biological organization ranges from simple to complex structures.

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

Shared Characteristics of Living and Nonliving Things

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

• Nonliving things: May have structure but lack metabolism 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.

• Example: Regulation of body temperature.

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.

Importance of DNA

• DNA stores genetic information and directs cellular activities.

• Essential for inheritance and protein synthesis.

Types of Bonds

• Ionic Bonds: Transfer of electrons between atoms.

• Covalent Bonds: Sharing of electrons between atoms.

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

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

Radioisotopes are 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

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

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

• Formula: for a cube.

Microscopy Types

• Light Microscopy: Used for viewing live cells and tissues.

• Electron Microscopy: Used for high-resolution imaging of cell structures.

Diffusion

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

• Passive process, no energy required.

• Example: Oxygen diffusing into cells.

Plasma Membrane Structure

• Composed of a phospholipid bilayer with embedded proteins.

• Selective permeability allows certain substances to pass.

Transport Across the Plasma Membrane

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

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

• Active Transport: Movement against concentration gradient, requires energy (ATP).

Isotonic Solutions

• Isotonic: Equal solute concentration inside and outside the cell.

• Cells retain their shape; no net water movement.

Glycolysis

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

• Occurs in the cytoplasm.

• Produces pyruvate, 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

• NADH and FADH2 are electron carriers.

• They receive electrons from metabolic intermediates.

Tissues & Organ Systems

Types of Tissues and Their Functions

Four main tissue types exist in the human body, each with specialized functions.

Types of Connective Tissues

• Loose connective tissue: Supports and binds other tissues.

• Dense connective tissue: Provides strength (e.g., tendons).

• Cartilage: Flexible support.

• Bone: Rigid support.

• Blood: Transport of substances.

Locations of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Bone, blood, cartilage.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, nerves.

Muscle Type 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.