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 membrane-bound organelles; includes animals, plants, fungi, and protists.

Hierarchy of Living Organisms

Biological organization ranges from simple to complex structures.

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organism

Shared Characteristics of Living and Nonliving Things

• Living things: Cellular organization, metabolism, homeostasis, growth, reproduction, response to stimuli, adaptation.

• Nonliving things: May have structure and mass, but lack the above characteristics.

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)

Elements vs. Molecules

• Element: Pure substance consisting of 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

• Used in medical imaging, cancer treatment, and biological research.

Reductionism

• Analyzing complex systems by studying their simpler components.

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

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

• 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

• Movement of molecules from high to low concentration.

• Passive process, no energy required.

Plasma Membrane Structure & Function

• Consists of a phospholipid bilayer with embedded proteins.

• Controls 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.

Active Transport

• Movement of substances against concentration gradient using energy (ATP).

• Example: Sodium-potassium pump.

Isotonic Solution

• Equal solute concentration inside and outside the cell.

• No net movement of water; cell maintains shape.

Glycolysis

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

• Produces ATP and NADH.

Electron Transport Chain & ATP Production

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

Electron Carriers in Citric Acid Cycle

• NAD+ and FAD are electron carriers.

• They gain electrons from metabolic intermediates.

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: Flexible support.

• Bone: Rigid support.

• Blood: Transport of substances.

Location of Each Tissue Type

• Epithelial: Skin, lining of digestive tract.

• Connective: Bones, tendons, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Type of Muscle 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.

Example: The stomach contains smooth muscle tissue, which contracts to mix and propel food.

Additional info: Academic context was added to clarify and expand brief review points, ensuring completeness and self-contained explanations.