Key Biological Terms and Definitions

Essential Vocabulary for General Biology

Understanding foundational terms is crucial for success in General Biology. Below are definitions and explanations of key concepts.

• 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 that has gained or lost one or more electrons, resulting in a net electrical charge.

• Covalent Bond: A chemical bond formed when two atoms share one or more pairs of electrons.

• 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 occurs in the digestion of polymers.

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

• Polymer: A large molecule 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 biological systems, energy is required for processes such as metabolism and movement.

• 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, often as a defense mechanism.

Fundamental Units and Classification

Basic Biological Organization

Biology is organized from the smallest units to complex systems. Classification helps organize living organisms.

• 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

Water's Role in Biology

Water is essential for life due to its unique properties. pH measures the acidity or basicity of solutions.

• 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), with 7 being neutral.

• Why Water is Dangerous to Drink (Sea Water): Sea water contains high levels of salt, which can disrupt cellular osmotic balance and lead to dehydration.

Cell Structure and Organelles

Functions of Cell Components

Cells contain specialized structures called organelles, each with distinct functions.

• 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.

• How Hydrogen Peroxide is Broken Down: Peroxisomes contain catalase, which converts hydrogen peroxide (H2O2) into water and oxygen.

• Functions of Cell Membrane: Regulates the movement of substances in and out of the cell, provides protection, and facilitates communication.

Genetics and Chromosomes

Genetic Material and Cell Division

Genetic information is stored in chromosomes, which are passed from parent to offspring.

• How Many Chromosomes Humans Have: Humans have 46 chromosomes (23 pairs).

• How Human Cells Have Flagella: Some human cells, such as sperm cells, possess flagella for movement.

Biochemistry: Enzymes, Polymers, and Fatty Acids

Chemical Reactions and Biological Molecules

Biological molecules undergo various chemical reactions essential for life.

• 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 between carbon atoms; unsaturated fatty acids have one or more double bonds, affecting their structure and function.

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

• Polymers and Monomers: Polymers are large molecules made of repeating units called monomers. Examples include proteins (monomers: amino acids), carbohydrates (monomers: monosaccharides), and nucleic acids (monomers: nucleotides).

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

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

• Why Denatured Proteins Hurt Humans: Denatured proteins lose their functional shape, which can disrupt biological processes.

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed from one form to another.

• What Affects Enzyme Activity: Temperature, pH, substrate concentration, and presence of inhibitors or activators.

Cell Membrane Structure and Function

Plasma Membrane Composition and Transport

The plasma membrane is a dynamic structure that controls the movement of substances and maintains cellular integrity.

• What Stabilizes Plasma Membrane: Cholesterol molecules interspersed within the membrane help maintain fluidity and stability.

• Why Phospholipids are Major Component: Phospholipids form a bilayer, providing a semi-permeable barrier essential for cell function.

• Isotonic, Hypotonic, Hypertonic Solutions:

  • Isotonic: Solute concentration is equal inside and outside the cell; no net water movement.

  • Hypotonic: Lower solute concentration outside the cell; water enters the cell, which may cause swelling.

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

Summary Table: Cell Membrane Transport Solutions

Comparison of Solution Types

Additional info:

• Some explanations and examples have been expanded for clarity and completeness.

• Scientific names and terms have been italicized where appropriate.