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 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 → Organisms → Populations → Communities → Ecosystems → Biosphere

Shared Characteristics of Living and Nonliving Things

• Living things: Composed of cells, capable of growth, reproduction, response to stimuli, metabolism, and homeostasis.

• Nonliving things: Lack cellular structure and biological processes.

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 Humans

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

• Calcium (Ca)

• Phosphorus (P)

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 Chemical Bonds

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions.

• 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

• Polar Molecules: Have uneven distribution of charge (e.g., water).

• Nonpolar Molecules: Have even distribution of charge (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 processes.

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

Cell organelles are specialized structures within cells, each with distinct functions.

Cell Size and Surface Area

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

• Smaller cells have a higher surface area-to-volume ratio, allowing efficient transport.

Microscopy Types

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

• Electron Microscopy: Used for high-resolution imaging of cell structures.

DNA Importance

• DNA: Stores genetic information; directs protein synthesis.

Diffusion

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

• Example: Oxygen diffusing into cells.

Plasma Membrane Structure

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

• Cells retain their normal shape in isotonic solutions.

ATP Production and Electron Transport Chain

• ATP Synthase: Protein complex where most ATP is produced during the electron transport chain.

Glycolysis

• Purpose: Breaks down glucose into pyruvate, producing ATP and NADH.

Citric Acid Cycle Electron Carriers

• NAD+ and FAD: Electron carriers; receive electrons from metabolic intermediates.

Tissues & Organ Systems

Types of Tissues and Their Functions

There are four main tissue types in the human body, each with specific functions.

Types of Connective Tissues

• Loose Connective Tissue: Supports and binds other tissues.

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

• Cartilage: Flexible support.

• Bone: Rigid support and protection.

• Blood: Transport of nutrients and waste.

Muscle Type in the Stomach

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

Types of Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Locations of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Bone, cartilage, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

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.