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, unicellular, often found in extreme environments; genetically distinct from bacteria.

• Eukarya: Eukaryotic organisms with a true nucleus; 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 → Organisms

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 only 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 an electronegative atom (e.g., O or N).

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

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

• Example: PET scans use radioactive tracers to visualize metabolic activity.

Reductionism

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

• Example: Studying cell organelles to understand cell function.

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Contains DNA; spherical.

• Mitochondria: Site of ATP production; oval-shaped.

• 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: Digestion of cellular waste; spherical.

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

• Chloroplasts: Photosynthesis (plants); oval-shaped.

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.

DNA Importance

• DNA stores genetic information, directs cell activities, and enables inheritance.

Diffusion

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

• Example: Oxygen diffuses into cells, carbon dioxide diffuses out.

Plasma Membrane Structure

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

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., H2O).

• 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 Solution

An isotonic solution has equal solute concentration as the cell, causing no net movement of water.

• Cells retain their shape in isotonic solutions.

Glycolysis Purpose

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

• Occurs in the cytoplasm.

ATP Production in Electron Transport Chain

• Most ATP is produced by the ATP synthase protein complex during oxidative phosphorylation.

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 Connective Tissues

• Loose Connective Tissue: Supports and binds other tissues.

• Dense Connective Tissue: Provides strength (e.g., tendons, ligaments).

• Adipose Tissue: Stores fat.

• Cartilage: Flexible support.

• Bone: Rigid support.

• Blood: Transport of substances.

Locations of Tissue Types

• Epithelial Tissue: Covers body surfaces, lines cavities.

• Connective Tissue: Found throughout the body, supporting organs.

• Muscle Tissue: Found in muscles, heart, digestive tract.

• Nervous Tissue: 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 Tissues and Their Functions

• Epithelial: Protection, absorption, secretion.

• Connective: Support, transport, storage.

• Muscle: Movement.

• Nervous: Communication, control.

Types of Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Table: Types of Cell Junctions

Table: Types of Connective Tissues

Additional info:

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

• Negatively charged elements (anions) attract positively charged elements (cations) to form ionic bonds.