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 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 → Cells → Tissues → Organs → Organ Systems → Organism → Population → Community → Ecosystem → 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 process by which living organisms maintain a stable internal environment despite external changes.

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

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.

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.

Importance of DNA

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

Types of Chemical Bonds

• Ionic Bonds: Formed when electrons are transferred between atoms.

• Covalent Bonds: Formed when atoms share electrons.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

Polarity of Molecules

• Polar Molecules: Unequal sharing of electrons; have partial positive and negative 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

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

• Example: PET scans use radioisotopes to visualize metabolic activity.

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 particles.

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

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

• Lysosomes: Digestion of cellular waste; spherical vesicles.

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

• Plasma Membrane: Controls entry and exit of substances; flexible boundary.

Cell Size and Surface Area

Cell size is limited by the surface area-to-volume ratio, which affects the efficiency of material exchange.

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

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.

Diffusion

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

• Example: Oxygen diffusing across cell membranes.

Plasma Membrane Structure

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

Transport Across the Plasma Membrane

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

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

• What can pass: Small, nonpolar molecules (e.g., O2, CO2).

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

Isotonic Solutions

• Isotonic solutions have equal solute concentration as the cell; no net water movement.

• Cells retain their normal shape in isotonic solutions.

Glycolysis

Glycolysis is the first step in cellular respiration, breaking down glucose to produce ATP.

• Occurs in the cytoplasm.

• Produces pyruvate, ATP, and NADH.

Electron Transport Chain and ATP Production

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

Citric Acid Cycle Electron Carriers

• NADH and FADH2 are electron carriers.

• They obtain electrons from oxidation of acetyl-CoA.

Tissues & Organ Systems

Types of Tissues and Their Functions

There are four main types of tissues in the human body, each with specialized functions.

• Epithelial Tissue: Covers surfaces, lines cavities, forms glands.

• Connective Tissue: Supports, protects, and binds other tissues.

• Muscle Tissue: Enables movement.

• Nervous Tissue: Conducts electrical impulses.

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 Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, fat, bone, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Muscle Type in the Stomach

• Smooth Muscle: Found in the walls of the stomach; involuntary control.

Types of Junctions

• Tight Junctions: Seal cells together, preventing leakage.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Tissues and Their Functions

Summary Table: Types of Cell Junctions

Key Equations

• Surface Area to Volume Ratio:

• pH Calculation: