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 without a nucleus.

• Archaea: Prokaryotic, unicellular, often found in extreme environments; genetically distinct from bacteria.

• Eukarya: Eukaryotic organisms with a 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 → Organism

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.

• Example: 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)

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

Types of Bonds

• Ionic Bonds: Transfer of electrons between atoms; forms charged ions.

• Covalent Bonds: Sharing of electrons between atoms.

• Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen).

Polarity

• 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: pH < 7

• Basic (Alkaline): pH > 7

• Neutral: pH = 7

Radioisotope Technology

• Used in medical imaging, cancer treatment, and biological research.

Atoms and Charge

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

• Negatively charged elements (anions) attract positively charged elements (cations).

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Stores DNA; round, central structure.

• Mitochondria: Produces ATP; oval with inner folds (cristae).

• Ribosomes: Protein synthesis; small, spherical.

• Endoplasmic Reticulum (ER): Synthesis and transport; rough (with ribosomes) or smooth (without).

• 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.

Cell Size and Surface Area

Smaller cells have a higher surface area-to-volume ratio, facilitating efficient exchange of materials.

• 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 images of cell structures.

• Fluorescence Microscopy: Used to visualize specific molecules with fluorescent tags.

Plasma Membrane Composition

• Phospholipid bilayer, proteins, cholesterol, carbohydrates.

Transport Across the Plasma Membrane

• Diffusion: Passive movement of molecules from high to low concentration.

• Active Transport: Movement against concentration gradient using energy (ATP).

• What can pass: Small, nonpolar molecules (e.g., O2, CO2).

• What cannot pass: Large, polar molecules and ions without transport proteins.

Isotonic Solutions

• Isotonic solutions have equal solute concentration as the cell; no net water movement.

• Cells retain their shape in isotonic solutions.

Chemical Reactions & Cellular Respiration

Glycolysis

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

• Produces ATP and NADH.

Electron Transport Chain

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

Citric Acid Cycle (Krebs Cycle)

• Electron carriers: NAD+ and FAD collect electrons from metabolic reactions.

• Electrons are transferred to the electron transport chain.

Tissues & Organ Systems

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces, lines cavities, protects, absorbs, and secretes.

• Connective Tissue: Supports, binds, and protects organs.

• Muscle Tissue: Contracts to produce movement.

• Nervous Tissue: Transmits electrical impulses.

Types of Connective Tissues

• Loose Connective Tissue: Cushions organs.

• Dense Connective Tissue: Forms tendons and ligaments.

• Adipose Tissue: Stores fat.

• Cartilage: Provides flexible support.

• Bone: Provides rigid support.

• Blood: Transports substances.

Location of Tissues

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, fat, bone, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Muscle Type in the Stomach

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

Types of Junctions

• Tight Junctions: Seal cells together, prevent leakage.

• Desmosomes: Anchor cells together.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Tissues and Their Functions

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