Glossary
Adhesion
The attraction between molecules of different substances.
Example:
Water climbing up a paper towel against gravity is an example of adhesion, as water molecules stick to the cellulose fibers.
Amino
A functional group (-NH2) consisting of a nitrogen atom bonded to two hydrogen atoms, which can act as a base by accepting a proton.
Example:
The amino group in an amino acid gives it basic properties, allowing it to accept H+ ions.
Amino acids
The monomeric building blocks of proteins, each containing an amino group, a carboxyl group, a hydrogen atom, and a unique R-group (side chain) attached to a central carbon atom.
Example:
There are 20 different common amino acids that can be combined in countless ways to form diverse proteins.
Carbohydrates
Macromolecules composed of carbon, hydrogen, and oxygen, primarily functioning as short-term energy storage and structural components.
Example:
Pasta provides your body with carbohydrates like starch, which are broken down into glucose for quick energy.
Carbonyl
A functional group (C=O) consisting of a carbon atom double-bonded to an oxygen atom, found in sugars.
Example:
Sugars like glucose and fructose contain a carbonyl group, which contributes to their reactivity.
Carboxyl
A functional group (-COOH) consisting of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group; it is acidic.
Example:
Amino acids contain a carboxyl group, which can donate a proton and act as an acid.
Cohesion
The attraction between molecules of the same substance, often due to hydrogen bonding.
Example:
Water droplets on a leaf demonstrate cohesion, as the water molecules stick together to form a spherical shape.
Covalent Bonds
Strong chemical bonds formed when two atoms share electrons, holding atoms together within a molecule.
Example:
The oxygen and hydrogen atoms within a single water molecule are held together by strong covalent bonds.
DNA
Deoxyribonucleic acid; a double-stranded nucleic acid that stores the genetic instructions for the development, functioning, growth, and reproduction of all known organisms.
Example:
Your unique genetic blueprint is encoded in the sequence of bases within your DNA.
Dehydration Synthesis
A chemical reaction that builds polymers by joining monomers, with the removal of a water molecule for each bond formed.
Example:
When your body builds muscle, amino acids are linked together via dehydration synthesis to form new protein strands.
Denaturing
The process by which a protein loses its specific three-dimensional shape and, consequently, its biological function, often due to changes in temperature, pH, or salinity.
Example:
Cooking an egg causes the proteins in the egg white to undergo denaturing, changing from clear liquid to solid white.
Evaporative Cooling
The process by which the evaporation of water from a surface removes heat, leading to a cooling effect.
Example:
When you sweat during exercise, the evaporative cooling of the sweat helps to lower your body temperature.
Functional Groups
Specific clusters of atoms within molecules that are responsible for the characteristic chemical reactions and properties of those molecules.
Example:
The presence of a hydroxyl (functional group) makes alcohols polar and able to form hydrogen bonds.
High Specific Heat
The amount of heat energy required to raise the temperature of a substance by a certain amount, which is high for water.
Example:
Oceans have a high specific heat, which helps moderate global temperatures and prevents drastic temperature swings.
Hydrogen Bonds
Weak intermolecular forces that form between a slightly positive hydrogen atom of one polar molecule and a slightly negative atom (like oxygen or nitrogen) of another polar molecule.
Example:
Hydrogen bonds are responsible for water's unique properties, like its ability to stick to itself and other surfaces.
Hydrolysis
A chemical reaction that breaks down polymers into monomers by adding a water molecule, which splits the bond.
Example:
During digestion, complex carbohydrates are broken down into simpler sugars through hydrolysis reactions.
Hydrophilic
Describes substances that are 'water-loving' and readily dissolve in or mix with water, typically due to their polarity.
Example:
Sugar is hydrophilic, which is why it easily dissolves when stirred into a glass of water.
Hydrophobic
Describes substances that are 'water-fearing' and do not dissolve in or mix with water, typically because they are nonpolar.
Example:
Oil is hydrophobic, which is why it separates into distinct layers when mixed with water.
Hydroxyl
A functional group (-OH) consisting of an oxygen atom bonded to a hydrogen atom, making molecules polar and capable of hydrogen bonding.
Example:
Alcohols and carbohydrates are rich in hydroxyl groups, making them soluble in water.
Lipids
A diverse group of hydrophobic macromolecules, including fats, oils, phospholipids, and steroids, primarily used for long-term energy storage, insulation, and cell membrane structure.
Example:
The cell membrane is primarily composed of lipids, specifically phospholipids, which create a barrier.
Macromolecules
Large, complex organic molecules essential for life, built from smaller repeating subunits.
Example:
Proteins, carbohydrates, lipids, and nucleic acids are the four major classes of macromolecules found in living organisms.
Monomers
Small, repeating molecular units that can be linked together to form larger polymers.
Example:
Amino acids are the monomers that link together to build a protein.
Nucleic Acids
Macromolecules that store and transmit genetic information, composed of nucleotide monomers.
Example:
DNA and RNA are the two main types of nucleic acids essential for heredity and protein synthesis.
Nucleotides
The monomeric building blocks of nucleic acids, each consisting of a five-carbon sugar, a phosphate group, and a nitrogenous base.
Example:
ATP, the energy currency of the cell, is a modified nucleotide.
Phosphate
A functional group (-PO4) consisting of a phosphorus atom bonded to four oxygen atoms, often found in nucleic acids and ATP, and carrying a negative charge.
Example:
The backbone of DNA is made of alternating sugar and phosphate groups.
Phospholipids
A type of lipid with a hydrophilic head (phosphate group) and two hydrophobic tails (fatty acids), forming the basic structure of cell membranes.
Example:
The cell membrane is a bilayer of phospholipids, with their hydrophilic heads facing the watery environments inside and outside the cell.
Polar molecule
A molecule with an unequal distribution of charge, resulting in a slightly positive end and a slightly negative end.
Example:
Water is a polar molecule because oxygen pulls electrons more strongly than hydrogen, creating distinct partial charges.
Polymers
Large molecules composed of many repeating monomer subunits linked together.
Example:
Starch is a polymer made up of many glucose monomers joined in a long chain.
Primary structure (protein)
The unique linear sequence of amino acids in a polypeptide chain, determined by genetic information.
Example:
The specific order of amino acids in a protein, like the sequence in insulin, defines its primary structure.
Proteins
Complex macromolecules made of amino acid monomers, performing a vast array of functions including catalyzing reactions, transport, structural support, and immune response.
Example:
Enzymes, which speed up chemical reactions in your body, are a type of protein.
Quaternary structure (protein)
The overall protein structure that results from the aggregation of two or more separate polypeptide chains (subunits).
Example:
Hemoglobin, which carries oxygen in red blood cells, exhibits quaternary structure because it is made of four distinct polypeptide chains.
RNA
Ribonucleic acid; a single-stranded nucleic acid that plays various roles in gene expression, including carrying genetic information from DNA to ribosomes and participating in protein synthesis.
Example:
Messenger RNA (mRNA) carries the instructions from a gene in the nucleus to the ribosomes in the cytoplasm to build a protein.
Saturated Fats
Lipids characterized by fatty acid chains with only single bonds between carbon atoms, making them solid at room temperature.
Example:
Butter contains a high proportion of saturated fats, which is why it remains solid at room temperature.
Secondary structure (protein)
Local folded structures that form within a polypeptide due to hydrogen bonding between atoms of the polypeptide backbone, commonly forming alpha-helices or beta-sheets.
Example:
The spiral shape of an alpha-helix in a protein is an example of its secondary structure.
Sulfhydryl
A functional group (-SH) consisting of a sulfur atom bonded to a hydrogen atom, important in stabilizing protein structure through disulfide bridges.
Example:
The sulfhydryl group in the amino acid cysteine allows proteins to form disulfide bonds, crucial for their 3D shape.
Surface Tension
The property of a liquid's surface that allows it to resist an external force, due to the cohesive forces between its molecules.
Example:
A water strider can walk on water due to the high surface tension created by the hydrogen bonds at the water's surface.
Tertiary structure (protein)
The overall three-dimensional shape of a single polypeptide chain, resulting from interactions between the R-groups of the amino acids.
Example:
The complex globular shape of an enzyme, allowing it to bind to its specific substrate, is its tertiary structure.
Unsaturated Fats
Lipids characterized by fatty acid chains containing one or more double bonds between carbon atoms, causing kinks and making them liquid at room temperature.
Example:
Olive oil is rich in unsaturated fats, contributing to its liquid state at room temperature.