Introduction to Biology

Domains of Life

The domain is the highest taxonomic rank in the classification of life. There are three domains:

• Bacteria: Single-celled prokaryotes with no nucleus.

• Archaea: Single-celled prokaryotes, distinct from bacteria, often found in extreme environments.

• Eukarya: Organisms with eukaryotic cells (with a nucleus), including animals, plants, fungi, and protists.

Example: Humans belong to the domain Eukarya.

Hierarchy of Living Organisms

Biological organization is structured from smallest to largest:

• Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

Additional info: This hierarchy helps understand complexity in biology.

Shared Characteristics of Living and Nonliving Things

• Living things exhibit organization, metabolism, homeostasis, growth, reproduction, and response to stimuli.

• Nonliving things may share some characteristics (e.g., organization) but lack others (e.g., metabolism, reproduction).

The Scientific Method

The scientific method is a systematic approach to inquiry:

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.

Chemistry of Life

Most Abundant Elements in Humans

• Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N), Calcium (Ca), Phosphorus (P)

Atoms, Elements, and Molecules

• Atom: Smallest unit of matter retaining properties of an element.

• Element: Substance made of one type of atom.

• Molecule: Two or more atoms bonded together.

Types of Chemical Bonds

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

• Covalent Bonds: Sharing of electron pairs between atoms.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., O or N).

Polarity of Molecules

• Polar Molecules: Unequal sharing of electrons, resulting in partial charges (e.g., water).

• Nonpolar Molecules: Equal sharing of electrons, no partial charges (e.g., O2).

Acids, Bases, and pH

• pH measures hydrogen ion concentration.

• pH < 7: Acidic; pH = 7: Neutral; pH > 7: Basic (alkaline).

Radioisotope Technology

• Radioisotopes are unstable isotopes that emit radiation.

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

Reductionism

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

Changing Atomic Charges

• Atoms gain or lose electrons to become ions (charged particles).

• Negatively charged elements (anions) attract positively charged elements (cations) to form ionic bonds.

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Contains DNA; spherical or oval.

• Mitochondria: Site of ATP production; rod-shaped.

• Endoplasmic Reticulum (ER): Rough ER (with ribosomes) synthesizes proteins; Smooth ER synthesizes lipids.

• Golgi Apparatus: Modifies, sorts, and packages proteins.

• Lysosomes: Contain digestive enzymes; spherical.

• Ribosomes: Protein synthesis; small, round.

• Plasma Membrane: Phospholipid bilayer controlling entry/exit of substances.

Cell Size and Surface Area

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

Formula:

Microscopy Types and Uses

• Light Microscopy: Observes living cells, general structure.

• Electron Microscopy: Higher resolution; Transmission EM for internal structures, Scanning EM for surfaces.

DNA Importance

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

Cell Membranes and Transport

Plasma Membrane Structure

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

What Can and Can't Pass Through the Plasma Membrane

• Small, nonpolar molecules (e.g., O2, CO2) pass easily.

• Large or charged molecules (e.g., ions, glucose) require transport proteins.

Diffusion

• Movement of molecules from high to low concentration until equilibrium is reached.

Active Transport

• Movement of substances against their concentration gradient, requiring energy (ATP).

Isotonic Solutions

• An isotonic solution has the same solute concentration as the cell; no net water movement, so cell size remains constant.

Cellular Respiration and Energy

Glycolysis

• First step in cellular respiration; breaks down glucose into pyruvate, producing ATP and NADH.

Electron Carriers in the Citric Acid Cycle

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

• They transfer electrons to the electron transport chain.

ATP Production and Protein Complex

• Most ATP is produced by ATP synthase during the electron transport chain.

Tissues & Organ Systems

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces, lines cavities, forms glands.

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

• Muscle Tissue: Produces 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.

Locations of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, fat, bone, blood.

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

• Nervous: Brain, spinal cord, nerves.

Muscle Type in the Stomach

• Smooth muscle is found in the stomach wall, enabling involuntary contractions.

Types of Cell Junctions

• Tight Junctions: Seal cells together to prevent leakage.

• Desmosomes: Anchor cells together, providing mechanical strength.

• Gap Junctions: Allow communication between cells via channels.

Summary Table: Tissue Types and Functions