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, 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 → Organisms → Populations → Communities → Ecosystems → Biosphere

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 exhibit some characteristics (e.g., movement), but lack cellular structure and metabolism.

Scientific Method

The scientific method is a systematic approach to investigation.

• Observation

• Hypothesis

• Experiment

• Data Collection

• Analysis

• 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.

Atoms, Elements, and Molecules

• Element: Pure substance consisting of one type of atom.

• Molecule: Two or more atoms bonded together.

Radioisotope Technology

Radioisotopes are used in medical imaging, cancer treatment, and biological research.

• Example: PET scans use radioactive tracers.

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 an electronegative atom (e.g., oxygen).

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

Charge Changes in Atoms

• Atoms 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

Cell organelles perform specialized functions within eukaryotic cells.

Cell Size and Surface Area

Cell size is limited by the surface area-to-volume ratio, which affects nutrient and waste exchange.

• Smaller cells have a higher surface area-to-volume ratio, allowing efficient transport.

• 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.

• Fluorescence Microscopy: Used to visualize specific molecules with fluorescent tags.

Plasma Membrane Structure and Function

• Composed of a phospholipid bilayer with embedded proteins.

• Regulates entry and exit of substances.

What Can and Can't Pass Through the Plasma Membrane

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

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

Types of Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication between cells.

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

Where Each Type of Tissue Is Found

• Epithelial: Skin, lining of digestive tract.

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

• Muscle: Skeletal muscles, heart, walls of organs.

• Nervous: Brain, spinal cord, nerves.

Type of Muscle in the Stomach

• Smooth Muscle: Involuntary, non-striated muscle found in the walls of the stomach and other internal organs.

Cellular Processes

Diffusion

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

• Important for gas exchange and nutrient transport.

Active Transport

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

• Example: Sodium-potassium pump.

Isotonic Solutions

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

• Cells retain their normal shape in isotonic solutions.

Cellular Respiration

Glycolysis

Glycolysis is the first step in cellular respiration, breaking down glucose into pyruvate and producing ATP.

• Occurs in the cytoplasm.

• Produces 2 ATP molecules per glucose.

Electron Transport Chain and ATP Production

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

• Location: Inner mitochondrial membrane.

Electron Carriers in the Citric Acid Cycle

• NAD+ and FAD are electron carriers.

• They gain electrons from metabolic reactions and transfer them to the electron transport chain.

Additional info: Expanded explanations and context were added for completeness and clarity, including inferred details about cell organelles, tissue types, and cellular processes.