Introduction to Biology

Domains of Life

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

• 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 → Organisms → Populations → Communities → Ecosystems → 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: Organization, metabolism, responsiveness, growth, development, reproduction.

• Nonliving: May have some characteristics (e.g., organization) but lack others (e.g., metabolism, 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.

• Example: Studying cell organelles to understand cell function.

DNA Importance

DNA (deoxyribonucleic acid) is the molecule that stores genetic information, guiding growth, development, and functioning.

• DNA is essential for inheritance and protein synthesis.

Types of Chemical Bonds

• Ionic Bonds: Formed when electrons are transferred between atoms, 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, 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 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 relative to volume, allowing efficient transport.

• Formula: for a cube

• Formula: for a cube

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 high to low concentration.

• Example: Oxygen diffusing into cells.

Plasma Membrane Structure

The plasma membrane is a selectively permeable barrier composed of a phospholipid bilayer with embedded proteins.

• Allows passage of small, nonpolar molecules (e.g., O2, CO2).

• Restricts large or charged molecules without transport proteins.

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 water movement.

• Cells retain their 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 & ATP Production

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

• Electron carriers (NADH, FADH2) donate electrons.

• Formula:

Tissues & Organ Systems

Types of Tissues and Their Functions

There are four main tissue types in the human body, each with specialized 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: Seal cells together, preventing leakage.

• Desmosomes: Anchor cells together, providing mechanical strength.

• Gap Junctions: Allow communication between cells via small molecules.

Location of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Bone, blood, cartilage.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, nerves, spinal cord.

Example: The stomach contains epithelial tissue (lining), connective tissue (support), smooth muscle (movement), and nervous tissue (control).

Additional info: Academic context and explanations were expanded for completeness and clarity, including inferred details about cell organelles, tissue types, and scientific method steps.