Introduction to Biology

Domains of Life

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

• Bacteria: Prokaryotic, unicellular organisms with simple cell structure.

• Archaea: Prokaryotic, often found in extreme environments; genetically distinct from bacteria.

• Eukarya: Eukaryotic organisms, including plants, animals, fungi, and protists; cells contain membrane-bound organelles.

Hierarchy of Living Organisms

Biological organization follows a hierarchical structure from smallest to largest.

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

Shared Characteristics of Living and Nonliving Things

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

• 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)

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 essential for growth, development, and reproduction.

• Directs protein synthesis and cellular functions.

Types of Chemical Bonds

• Ionic Bonds: Formed by transfer of electrons between atoms.

• Covalent Bonds: Formed by sharing of electrons.

• Hydrogen Bonds: Weak attractions between hydrogen and electronegative atoms (e.g., oxygen, nitrogen).

Polarity of Molecules

• Polar molecules: Unequal sharing of electrons; have partial charges (e.g., water).

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

Acids, Bases, and pH

• Acidic substances: pH < 7

• Basic substances: pH > 7

• Neutral: pH = 7

Radioisotope Technology

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

• Radioisotopes can trace biochemical pathways.

Atoms and Charge

• Atoms change charge by gaining or losing electrons, forming ions.

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

Elements vs. Molecules

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

• Molecule: Two or more atoms bonded together.

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

Cell organelles perform specialized functions within eukaryotic cells.

• Nucleus: Stores DNA; spherical shape.

• Mitochondria: Site of ATP production; oval shape.

• Ribosomes: Protein synthesis; small, round.

• Endoplasmic Reticulum (ER): Synthesis of proteins (rough ER) and lipids (smooth ER); tubular network.

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

• Lysosomes: Digestive enzymes; spherical vesicles.

• Chloroplasts: Photosynthesis (in plants); oval shape.

• Plasma Membrane: Controls entry/exit; flexible boundary.

Cell Size and Surface Area

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

• Smaller cells have higher surface area relative to volume, allowing efficient transport.

Microscopy Types

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

• Electron Microscopy: High resolution; used for detailed cell structures.

• Fluorescence Microscopy: Visualizes specific molecules using fluorescent tags.

Diffusion

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

• Important for gas exchange and nutrient transport.

Plasma Membrane Structure

• Composed of phospholipid bilayer, proteins, cholesterol, and carbohydrates.

• Selective permeability 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), some small polar molecules (e.g., water).

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

Active Transport

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

• Example: Sodium-potassium pump.

Isotonic Solutions

• Isotonic solution: Equal solute concentration inside and outside the cell; no net water movement.

• Cells retain their normal shape.

Cellular Respiration & Metabolism

Glycolysis

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

• Occurs in the cytoplasm.

• Produces 2 ATP and 2 NADH per glucose molecule.

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 gain electrons from metabolic intermediates and transfer them to the electron transport chain.

Tissues & Organ Systems

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces; protection, absorption, secretion.

• Connective Tissue: Supports and connects other tissues; includes bone, blood, cartilage.

• Muscle Tissue: Movement; includes skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Communication; transmits electrical impulses.

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 nutrients and gases.

Location of Each Tissue Type

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, bones, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Type of Muscle in the Stomach

• Smooth muscle is found in the stomach, responsible for involuntary contractions.

Types of Junctions

• Tight junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap junctions: Allow communication between cells.

Additional info:

• Some details (e.g., specific electron carriers, ATP synthase) were inferred for completeness.

• Table summarizes tissue types, functions, and locations for clarity.