Introduction to Biology

Domains of Life

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

• 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 ranges from simple to complex structures.

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

• Each level builds upon the previous, increasing complexity and specialization.

Shared Characteristics of Living and Nonliving Things

• Living things exhibit organization, metabolism, responsiveness, growth, development, reproduction, and homeostasis.

• 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.

• Examples: Regulation of body temperature, blood pH, and glucose levels.

Chemistry of Life

Most Abundant Elements in Humanity

• Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S)

• These elements form the basis of biological molecules.

Reductionism

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

• Helps in analyzing biological processes at molecular and cellular levels.

Importance of DNA

• DNA stores genetic information, directs protein synthesis, and enables inheritance.

• Its structure allows for replication and mutation, driving evolution.

Types of Bonds

• Ionic Bonds: Formed by transfer of electrons between atoms; creates charged ions.

• Covalent Bonds: Formed by sharing electrons between atoms; strong and stable.

• Hydrogen Bonds: Weak attractions between partially charged atoms, important in water and DNA structure.

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.

• Radioisotopes emit radiation, allowing tracking of molecules in cells.

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 essential for cell survival.

• Nucleus: Stores DNA; spherical shape.

• Mitochondria: Site of ATP production; oval shape.

• Ribosomes: Protein synthesis; small, round.

• Endoplasmic Reticulum (ER): Protein and lipid synthesis; network of membranes.

• Golgi Apparatus: Modifies, sorts, and packages proteins; stack of flattened sacs.

• Lysosomes: Digestion of cellular waste; spherical.

• Plasma Membrane: Controls entry/exit; flexible, phospholipid bilayer.

Cell Size and Surface Area

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

• As cell size increases, surface area grows slower than volume.

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 molecules.

Element vs. Molecule

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

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

Cell Membrane & Transport

Plasma Membrane Structure

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

• Provides selective permeability and structural support.

Diffusion

• Movement of molecules from high to low concentration.

• Passive process, does not require energy.

Active Transport

• Movement of molecules against concentration gradient, requires energy (ATP).

• Examples: 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, and most polar molecules without transport proteins.

Isotonic Solution

• Has equal solute concentration as the cell; no net movement of water.

• Cells retain their normal shape in isotonic solutions.

Cellular Respiration

Glycolysis

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

• Occurs in the cytoplasm; produces ATP and NADH.

Electron Transport Chain & ATP Production

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

• Located in the inner mitochondrial membrane.

Electron Carriers in Citric Acid Cycle

• NAD+ and FAD are electron carriers.

• They collect electrons from metabolic reactions and deliver them to the electron transport chain.

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: Enables movement; includes skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Conducts electrical impulses; found in brain, spinal cord, nerves.

Types of Connective Tissues

• Loose Connective Tissue: Cushions organs.

• Dense Connective Tissue: Forms tendons and ligaments.

• Adipose Tissue: Stores fat.

• Cartilage: Provides flexible support.

• Bone: Provides rigid support.

• Blood: Transports substances.

Location of Each Tissue Type

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, fat, bone, blood.

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

• Nervous: Brain, spinal cord, peripheral nerves.

Type of Muscle in the Stomach

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

Types of Junctions

• Tight Junctions: Seal cells together, prevent leakage.

• Desmosomes: Provide mechanical strength, anchor cells.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Tissues and Their Functions

Summary Table: Types of Cell Junctions

Summary Table: Types of Bonds

Key Equations

• Surface Area to Volume Ratio:

• ATP Production (Cellular Respiration):

Example: In the stomach, smooth muscle contracts to mix food and aid digestion.

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