Introduction to Biology

Domains of Life

The domain system classifies all living organisms into three major groups based on cellular organization and genetic 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 → Organelles → Cells → Tissues → Organs → Organ Systems → Organism

Shared Characteristics of Living and Nonliving Things

• Living things: Exhibit growth, reproduction, metabolism, response to stimuli, and homeostasis.

• Nonliving things: May have structure and mass but lack 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.

• Example: Regulation of body temperature.

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 and directs cellular activities.

• Essential for inheritance, protein synthesis, and cell division.

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 hydrogen and electronegative atoms (e.g., oxygen, nitrogen).

Polarity of Molecules

• Polar molecules: Unequal sharing of electrons; have partial charges (e.g., water).

• Nonpolar molecules: Equal sharing of electrons; no charge separation (e.g., methane).

Acids, Bases, and pH

• Acidic substances: pH < 7

• Basic substances: pH > 7

• Neutral: pH = 7

Radioisotope Technology

• 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): Protein and lipid synthesis; network of membranes.

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

• Lysosomes: Digestive enzymes; spherical vesicles.

• Plasma Membrane: Controls entry/exit; flexible boundary.

• Chloroplasts: Photosynthesis (plants); oval shape.

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.

• Formula: (for a cube),

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.

Plasma Membrane Structure

• Composed of a phospholipid bilayer with embedded proteins.

• Selective permeability regulates transport.

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.

Diffusion

• Movement of molecules from high to low concentration.

• Passive process; no energy required.

Active Transport

• Movement of substances against concentration gradient using energy (ATP).

• Example: Sodium-potassium pump.

Isotonic Solutions

• Equal solute concentration inside and outside the cell.

• No net movement of water; cell shape remains unchanged.

Chemical Reactions in Cells

Glycolysis

• First step in cellular respiration; breaks down glucose into pyruvate.

• Produces ATP and NADH.

Electron Transport Chain and ATP Production

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

• Electron carriers (NADH, FADH2) donate electrons to the chain.

Citric Acid Cycle Electron Carriers

• NAD+ and FAD collect electrons during the cycle, becoming NADH and FADH2.

Tissues & Organ Systems

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces; protection, absorption, secretion.

• Connective Tissue: Supports and connects; includes bone, blood, cartilage.

• Muscle Tissue: Movement; includes skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Communication; neurons and supporting cells.

Types of Connective Tissues

• Loose connective tissue: Supports organs.

• Dense connective tissue: Forms tendons and ligaments.

• Cartilage: Flexible support.

• Bone: Rigid support.

• Blood: Transport of substances.

Location of Each Tissue Type

• Epithelial: Skin, lining of organs.

• Connective: Throughout body; bones, blood, cartilage.

• Muscle: Skeletal muscles, heart, walls of organs.

• Nervous: Brain, spinal cord, nerves.

Type of Muscle in the Stomach

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

Types of Junctions

• Tight junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap junctions: Allow communication between cells.

Summary Table: Types of Tissues and Their Functions

Additional info: Academic context was added to expand brief points and ensure completeness for exam preparation.