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 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 ranges from simple to complex structures.

• Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

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 stable internal conditions despite external changes.

• Example: Regulation of body temperature, blood glucose levels.

Shared Characteristics of Living and Nonliving Things

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

• Nonliving things: May have structure but lack 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 organelles to understand cell function.

Atoms, Elements, and Molecules

• Atom: Smallest unit of matter.

• 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.

Changing Atomic Charges

• Atoms gain or lose electrons to become ions.

• Cation: Positively charged (lost electrons).

• Anion: Negatively charged (gained electrons).

Types of Chemical 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

• Polar Molecule: Unequal sharing of electrons, resulting in partial charges (e.g., water).

• Nonpolar Molecule: Equal sharing of electrons, no charge separation (e.g., methane).

Acids, Bases, and pH

• Acidic: pH < 7

• Basic (Alkaline): pH > 7

• Neutral: pH = 7

Interaction of Charged Elements

• 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 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.

• Fluorescence Microscopy: Used to visualize specific proteins or structures with fluorescent tags.

DNA Importance

• DNA stores genetic information necessary for cell function and inheritance.

• Directs protein synthesis.

Chemical Processes in Cells

Diffusion

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

• Occurs across cell membranes.

• Example: Oxygen and carbon dioxide exchange in lungs.

Plasma Membrane Structure

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

• Controls permeability and communication.

Transport Across Membranes

• Passive Transport: Diffusion, osmosis; no energy required.

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

• Example: Sodium-potassium pump.

What Can and Can't Pass Through the Plasma Membrane

• Can pass: Small, nonpolar molecules (O2, CO2), some small polar molecules (water).

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

Isotonic Solutions

• Isotonic: Solution with equal solute concentration as the cell; no net water movement.

• Effect: Cell maintains normal shape.

Cellular Respiration

Glycolysis

• First step in cellular respiration; breaks down glucose into pyruvate.

• Produces ATP and NADH.

• Occurs in cytoplasm.

Electron Transport Chain (ETC)

• Most ATP is produced in the ETC, located in the inner mitochondrial membrane.

• Protein Complex: ATP synthase.

Citric Acid Cycle Electron Carriers

• NADH and FADH2 are electron carriers.

• They receive electrons from metabolic reactions and deliver them to the ETC.

Tissues & Organ Systems

Types of Tissues and Their Functions

Types of Connective Tissues

• Loose Connective Tissue: Supports organs.

• Dense Connective Tissue: Forms tendons and ligaments.

• Cartilage: Provides flexible support.

• Bone: Structural support.

• Blood: Transport of nutrients and gases.

Locations of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Bone, cartilage, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Muscle Type in the Stomach

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

Types of Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication between cells.