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. Question

3. Hypothesis

4. Experiment

5. Data Collection

6. Analysis

7. Conclusion

Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes.

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

Characteristics of Living vs. Nonliving Things

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

• Nonliving: Lack of cellular structure, metabolism, or reproduction.

Chemistry of Life

Most Abundant Elements in Humans

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

• Calcium (Ca)

• Phosphorus (P)

Reductionism

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

Importance of DNA

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

Types of Chemical Bonds

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

• Covalent Bonds: Formed by sharing electrons between atoms.

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

Polarity of Molecules

• 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.

Atoms and Charge

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

• Negatively charged ions (anions) attract positively charged ions (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.

Cell Size and Surface Area

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

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

Microscopy Types

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).

• Can't Pass: Large molecules, ions, and most polar substances without transport proteins.

Types of Junctions

Chemical Processes in Cells

Diffusion

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

• Occurs across cell membranes for gases and small molecules.

Active Transport

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

• Example: Sodium-potassium pump.

Isotonic Solutions

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

• Cells retain their normal shape in isotonic solutions.

Cellular Respiration

Glycolysis

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

• Occurs in the cytoplasm.

• Produces 2 ATP molecules per glucose.

Electron Transport Chain and 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 reactions and transfer them to the electron transport chain.

Tissues & Organ Systems

Types of Connective Tissues

Types of Tissues and Their Functions

Muscle Type in the Stomach

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

Where to Find Each Tissue Type

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, ligaments, fat, bone, blood.

• Muscle: Skeletal (attached to bones), cardiac (heart), smooth (walls of organs).

• Nervous: Brain, spinal cord, peripheral nerves.

Additional info:

• ATP synthase is the protein complex where most ATP is generated during oxidative phosphorylation.

• Diffusion and active transport are fundamental for maintaining cellular homeostasis.

• Radioisotope technology is used for diagnostic imaging (e.g., PET scans) and cancer therapy.