Key Biological Terms and Definitions

Introduction

This section covers essential definitions and terms foundational to General Biology. Understanding these concepts is crucial for grasping more advanced topics in cell biology, biochemistry, and physiology.

• Hypothesis: A testable statement or prediction about the natural world, often used as the basis for scientific experiments.

• Atomic Number: The number of protons in the nucleus of an atom, which determines the element's identity.

• Ion: An atom or molecule with a net electric charge due to the loss or gain of electrons.

• Covalent Bond: A chemical bond formed by the sharing of electron pairs between atoms.

• Cilia: Short, hair-like structures on the surface of some cells that aid in movement or sensory functions.

• Isomer: Molecules with the same chemical formula but different structural arrangements.

• Hydrolysis Reaction: A chemical reaction in which water is used to break down a compound; commonly involved in the breakdown of polymers.

• Dehydration Reaction: A chemical reaction that involves the loss of a water molecule from the reacting molecule; often used to build polymers from monomers.

• Polymer: Large molecules composed of repeating subunits called monomers.

• Essential Amino Acids: Amino acids that cannot be synthesized by the body and must be obtained from the diet.

• Energy: The capacity to do work; in biology, energy is required for cellular processes.

• Diffusion: The passive movement of molecules from an area of higher concentration to an area of lower concentration.

• Osmosis: The diffusion of water across a selectively permeable membrane.

• Phagocytosis: The process by which a cell engulfs large particles or other cells.

Basic Units and Classification in Biology

Introduction

Understanding the organization and classification of life is fundamental in biology. This section reviews the smallest unit of life, scientific naming, and classification systems.

• Smallest Unit of Life: The cell is the basic structural and functional unit of all living organisms.

• Scientific Name for Humans: Homo sapiens

• Classification Categories in Order: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Octet Rule: Atoms tend to gain, lose, or share electrons to achieve a full set of eight valence electrons.

• Reactivity of an Atom: Determined by the number of electrons in its outermost shell.

Properties of Water and pH

Introduction

Water is essential for life, and its properties influence biological systems. pH measures the acidity or basicity of solutions, affecting cellular processes.

• Why Water is Neutral: Pure water has equal concentrations of hydrogen ions (H+) and hydroxide ions (OH-), resulting in a pH of 7.

• pH Scale: Ranges from 0 (most acidic) to 14 (most basic); pH 7 is neutral.

• Why Sea Water is Dangerous to Drink: High salt content can disrupt cellular osmotic balance, leading to dehydration.

Cell Structure and Organelles

Introduction

Cells contain specialized structures called organelles that perform distinct functions necessary for life. Understanding these organelles is key to cell biology.

• Peroxisome: Breaks down fatty acids and detoxifies harmful substances.

• Vacuole: Stores nutrients, waste products, and helps maintain turgor pressure in plant cells.

• Nucleolus: Located within the nucleus; responsible for ribosome synthesis.

• Hydrogen Peroxide Breakdown: Catalase enzyme in peroxisomes converts hydrogen peroxide (H2O2) into water and oxygen.

• Functions of Cell Membrane: Regulates entry and exit of substances, provides protection, and facilitates communication.

Genetics and Chromosomes

Introduction

Genetics is the study of heredity and variation. Chromosomes carry genetic information essential for inheritance.

• Number of Chromosomes in Humans: Humans have 46 chromosomes (23 pairs).

• Human Cells with Flagella: Sperm cells possess flagella for motility.

Biochemistry: Enzymes, Lipids, and Fatty Acids

Introduction

Biochemical reactions are catalyzed by enzymes, and lipids play vital roles in cell structure and energy storage.

• How Penicillin Kills Bacteria: Penicillin inhibits the synthesis of bacterial cell walls, leading to cell lysis.

• Differences Between Saturated and Unsaturated Fatty Acids: Saturated fatty acids have no double bonds; unsaturated fatty acids have one or more double bonds, affecting fluidity.

• Why Margarine is Solid: Contains saturated fats, which are solid at room temperature.

Polymers and Monomers

Introduction

Polymers are large molecules made from repeating units called monomers. Understanding their structure is important in biochemistry.

• Polymers and Monomers of Each:

  • Proteins: Polymers of amino acids.

  • Carbohydrates: Polymers of monosaccharides (e.g., glucose).

  • Nucleic Acids: Polymers of nucleotides.

• Levels of Protein Organization: Primary, secondary, tertiary, and quaternary structures.

• How Many Amino Acids There Are: 20 standard amino acids.

• Why Penicillin Doesn't Hurt Humans: Human cells lack peptidoglycan cell walls, which penicillin targets.

Thermodynamics and Energy in Biology

Introduction

Energy transformations are governed by the laws of thermodynamics, which apply to biological systems.

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

• Why Enzymes Work: Enzymes lower the activation energy required for reactions, increasing reaction rates.

• What Affects Enzyme Activity: Temperature, pH, substrate concentration, and inhibitors.

Cell Membrane Structure and Function

Introduction

The plasma membrane is a selectively permeable barrier that maintains cellular integrity and mediates communication.

• What Stabilizes Plasma Membrane: Cholesterol molecules interspersed within the phospholipid bilayer.

• Why Phospholipids are Major Component: Their amphipathic nature (hydrophilic head, hydrophobic tail) forms the bilayer structure.

• Isotonic, Hypotonic, Hypertonic Solutions:

  • Isotonic: Equal solute concentration inside and outside the cell; no net water movement.

  • Hypotonic: Lower solute concentration outside the cell; water enters the cell, possibly causing swelling.

  • Hypertonic: Higher solute concentration outside the cell; water leaves the cell, causing shrinkage.

Summary Table: Cell Membrane Solutions

Comparison of Solution Types

Additional info:

• Scientific names are always italicized and consist of genus and species (e.g., Homo sapiens).

• Enzyme activity can be described by the Michaelis-Menten equation:

• Protein structure levels:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helices and beta sheets.

  • Tertiary: 3D folding of a single polypeptide.

  • Quaternary: Association of multiple polypeptides.