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.

• Archaea: Prokaryotic, often found in extreme environments.

• Eukarya: Eukaryotic, includes plants, animals, fungi, and protists.

Hierarchy of Living Organisms

Biological organization follows a hierarchy from smallest to largest:

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organism

Shared Characteristics of Living and Nonliving Things

• Living things: Growth, reproduction, response to stimuli, metabolism, cellular organization, homeostasis.

• Nonliving things: May exhibit some properties (e.g., movement) but lack cellular structure and metabolism.

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)

Elements vs. Molecules

• Element: Pure substance consisting of one type of atom (e.g., O2).

• Molecule: Two or more atoms bonded together (e.g., H2O).

Types of Bonds

• Ionic Bonds: Transfer of electrons between atoms, forming charged ions.

• Covalent Bonds: Sharing of electrons between atoms.

• Hydrogen Bonds: Weak attraction between a hydrogen atom and another electronegative atom.

Polarity

• 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 due to their radioactive properties.

Reductionism

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

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: Contains DNA; round, central structure.

• Mitochondria: Site of ATP production; 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 vesicles.

• Plasma Membrane: Controls entry/exit; flexible, phospholipid bilayer.

• Chloroplasts: Photosynthesis (plants); oval with internal stacks.

Cell Size and Surface Area

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

Microscopy Types

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

• Electron Microscopy: High resolution for detailed cell structures.

• Fluorescence Microscopy: Visualizes specific molecules using fluorescent tags.

DNA Importance

DNA stores genetic information, directs protein synthesis, and is essential for inheritance.

Diffusion

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

• Example: Oxygen moving into cells.

Plasma Membrane Structure

• Composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

Transport Across the Plasma Membrane

• Passive Transport: 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

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

Chemical Energy & Cellular Respiration

Glycolysis

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

Electron Transport Chain & ATP Production

• Most ATP is produced by 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 intermediates during the cycle.

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: Flexible support.

• Bone: Rigid support.

• Blood: Transports substances.

Location of Each Tissue Type

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, fat, bone, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Type of Muscle in the Stomach

• Smooth Muscle: Involuntary, found in walls of stomach and other organs.

Types of Junctions

• Tight Junctions: Seal cells together, prevent leakage.

• Desmosomes: Anchor cells, provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Tissues and Their Functions

Summary Table: Cell Organelles

Key Equations

• Surface Area to Volume Ratio:

• $\text{Surface Area to Volume Ratio} = \frac{\text{Surface Area}}{\text{Volume}}$

• ATP Production (Cellular Respiration):

• $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$

• pH Calculation:

• $\text{pH} = -\log_{10}[\text{H}^+]$

Additional info: Academic context was added to clarify and expand on brief review points, including definitions, examples, and tables for cell organelles and tissue types.