Introduction to Biology

Domains of Life

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

• Bacteria: Single-celled prokaryotes with no nucleus.

• Archaea: Single-celled prokaryotes, often found in extreme environments; genetically distinct from bacteria.

• Eukarya: Organisms with cells containing a nucleus; includes animals, plants, fungi, and protists.

Hierarchy of Living Organisms

Biological organization follows a hierarchy from smallest to largest:

• Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → 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 mass but lack cellular organization and 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.

• 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)

Elements vs. Molecules

• Element: Pure substance consisting of only one type of atom (e.g., O2).

• Molecule: Two or more atoms bonded together (e.g., H2O).

Types of 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 another electronegative atom.

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

Radioisotopes are used in medical imaging, cancer treatment, and biological research due to their radioactive properties.

Reductionism

Reductionism is the approach of understanding complex systems by studying their simpler components.

Atoms and Charge

• Atoms can gain or lose electrons to become ions.

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

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Contains genetic material (DNA); round shape.

• Mitochondria: Site of ATP production; oval shape.

• Ribosomes: Protein synthesis; small, spherical.

• Endoplasmic Reticulum (ER): Rough ER (with ribosomes) synthesizes proteins; Smooth ER synthesizes lipids.

• Golgi Apparatus: Modifies, sorts, and packages proteins; stack-like structure.

• Lysosomes: Digestive enzymes; spherical.

• Plasma Membrane: Controls entry and exit of substances; flexible, phospholipid bilayer.

Cell Size and Surface Area

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

Microscopy Types

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

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

DNA Importance

DNA stores genetic information necessary for cell function, growth, and reproduction.

Chemical Processes in Cells

Diffusion

Diffusion is the movement of molecules from an area of higher concentration to lower concentration.

Plasma Membrane Structure

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

Transport Across the Plasma Membrane

• Passive Transport: No energy required; includes diffusion and facilitated diffusion.

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

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

• What cannot pass: Large or charged molecules (e.g., ions, glucose) without transport proteins.

Isotonic Solutions

An isotonic solution has equal solute concentration inside and outside the cell, resulting in no net movement of water.

Glycolysis

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

Electron Transport Chain and ATP Production

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

Citric Acid Cycle Electron Carriers

• NADH and FADH2 are electron carriers, receiving electrons from metabolic intermediates.

Tissues & Organ Systems

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces, lines cavities, forms glands.

• Connective Tissue: Supports, protects, and binds other tissues.

• Muscle Tissue: Contracts to produce movement.

• Nervous Tissue: Transmits electrical impulses.

Types of Connective Tissues

• Loose Connective Tissue: Provides support and flexibility.

• Dense Connective Tissue: Forms tendons and ligaments.

• Adipose Tissue: Stores fat.

• Cartilage: Provides cushioning.

• Bone: Structural support.

• Blood: Transports substances.

Location of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, ligaments, fat, bone, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Muscle Type in the Stomach

• Smooth Muscle: Found in the walls of the stomach; involuntary control.

Types of Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• 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 expand brief review points into full explanations, including definitions, examples, and tables for clarity.