Elements
The fundamental substances that make up all matter, consisting of atoms of the same atomic number.
Biological molecules
Molecules made up of oxygen, carbon, hydrogen, and nitrogen used to build carbohydrates, proteins, lipids, and nucleic acids.
Trace elements
Elements required by an organism in small quantities, including iron, iodine, and copper.
Storage compounds
Compounds made up of oxygen, carbon, hydrogen, and nitrogen used to store energy in organisms.
Cells
Basic unit of life, made up of oxygen, carbon, hydrogen, and nitrogen.
Elements
Substances made up of one type of atom, including oxygen, carbon, hydrogen, nitrogen, and others.
Atoms
The unit of life and building blocks of the physical world.
Protons
Positively charged (+) particles.
Neutrons
Uncharged particles.
Electrons
Negatively charged (–) particles.
Isotopes
Atoms with the same number of protons but different number of neutrons in the nucleus.
Compounds
A substance consisting of two or more elements that are chemically bonded together.
Chemical bonds
The force that holds two atoms together in a molecule.
Ions
Charged forms of atoms that are formed when one or more electrons are transferred from one atom to another.
Ionic bond
A chemical bond formed between two atoms when one or more electrons are transferred from one atom to the other.
Covalent bond
A chemical bond formed when electrons are shared between atoms.
Non-polar covalent bond
A covalent bond where electrons are shared equally between the atoms.
Polar covalent bond
A covalent bond where electrons are shared unequally between the atoms.
Acidic Solution
A solution that contains a lot of hydrogen ions (H+).
Basic Solution
A solution that contains a lot of hydroxide ions (OH–).
pH Scale
A scale used to measure the acidity or alkalinity of a solution, numbered from 1 to 14, with 7 considered neutral pH.
Hydrogen Ion Concentration
The concentration of hydrogen ions in a solution, which indicates whether it is acidic, basic, or neutral.
pH Formula
The formula used to calculate the pH of a solution, which is pH = –log [H+].
Logarithmic Scale
A scale in which each unit represents a tenfold change in hydrogen ion concentration on the pH scale.
Organic molecules
Molecules with carbon atoms
Inorganic compounds
Molecules that do not contain carbon atoms
Carbon
A versatile atom that can bind with other carbons, nitrogen, oxygen, and hydrogen
Polymers
Chains of building blocks in macromolecules
Monomers
Individual building blocks of a polymer
Dehydration synthesis
A reaction that forms polymers by losing a water molecule
Hydrolysis
A reaction that breaks down polymers into monomers by adding a water molecule
Carbohydrates, proteins, lipids, nucleic acids
Four classes of organic compounds central to life on Earth
Carbohydrates
Organic compounds containing carbon, hydrogen, and oxygen that are categorized as monosaccharides, disaccharides, or polysaccharides.
Monosaccharides
Simple sugars that are an energy source for cells and include glucose and fructose with a chemical formula of C6H12O6.
Disaccharides
Sugars formed by joining two monosaccharides with a glycosidic linkage, such as maltose, and can be broken down into two monosaccharides by adding water.
Polysaccharides
Complex carbohydrates made up of many repeated units of monosaccharides, such as starch, cellulose, and glycogen.
Starch
A polysaccharide that stores sugar in plants.
Cellulose
A polysaccharide made up of β-glucose and is a major part of the cell walls in plants, lending structural support.
Glycogen
A polysaccharide that stores sugar in animals.
Chitin
A polymer of β-glucose molecules that serves as a structural molecule in the walls of fungus and in the exoskeletons of arthropods.
Polypeptides
Organic compounds formed by joining a group of amino acids together in a "string" through peptide bonds. Once they twist and fold on themselves, they form a 3D structure called a protein.
Lipids
Organic compounds consisting of carbon, hydrogen, and oxygen atoms. They function as structural components of cell membranes, sources of insulation, signalling molecules, and a means of energy storage.
Phospholipids
Lipids with two hydrophobic fatty acid tails and one hydrophilic phosphate head. They have both hydrophobic and hydrophilic properties, making them amphipathic molecules.
Cholesterol
A four-ringed molecule found in membranes that generally increases membrane fluidity, except at very high temperatures. It is also important for making certain types of hormones and for making vitamin D.
Nucleic Acids
Molecules made up of simple units called nucleotides that contain carbon, hydrogen, oxygen, nitrogen, and phosphorus. DNA contains the hereditary "blueprints" of all life, while RNA is essential for protein synthesis.
Surface Area-to-Volume Ratio
The concept that as cells or organisms increase in size, their surface area-to-volume ratio decreases, leading to less efficient exchange of materials. Small organisms lose heat at much higher rates than larger organisms due to their efficient exchange of heat.
Prokaryotic Cells
Cells that lack a nucleus and other membrane-bound organelles. They are typically smaller and simpler in structure than eukaryotic cells.
Eukaryotic Cells
Cells that contain a nucleus and other membrane-bound organelles. They are typically larger and more complex in structure than prokaryotic cells.
Prokaryotic cell
A type of cell that is smaller and simpler than a eukaryotic cell, with no membrane-bound organelles. Bacteria and archaea are examples of prokaryotes.
Eukaryotic cell
A type of cell that is more complex than a prokaryotic cell and has many smaller structures called organelles. Fungi, protists, plants, and animals are examples of eukaryotes.
Plasma membrane
The outer envelope of the cell, made up of mostly phospholipids and proteins. It regulates the movement of substances into and out of the cell and is semipermeable.
Nucleus
The largest organelle in the cell that contains the cell's genetic material (DNA) and is responsible for directing the cell's activities and reproduction.
Ribosomes
Sites of protein synthesis in the cell, composed of two subunits (large and small) made of ribosomal RNA (rRNA) and proteins. They can be free-floating or attached to the endoplasmic reticulum (ER).
Endoplasmic reticulum (ER)
A continuous channel that extends into many regions of the cytoplasm and provides mechanical support and transportation. The rough ER compartmentalizes the cell, while the smooth ER makes lipids and breaks down toxic chemicals.
Golgi complex
An organelle that modifies, processes, and sorts proteins synthesized by ribosomes on the rough ER. It packages the final products in vesicles for distribution outside of the cell.
Mitochondria
Organelles responsible for converting energy from organic molecules into ATP, the most common energy molecule in the cell. They have an inner and outer membrane, with the inner membrane forming folds called cristae.
Lysosomes
Organelles that contain digestive enzymes used to break down old, worn-out org
Passive Transport
Movement of molecules down a concentration gradient without the use of energy.
Simple Diffusion
Movement of small, hydrophobic molecules across the cell membrane without the assistance of proteins.
Facilitated Diffusion
Movement of molecules across the cell membrane with the assistance of channel-type proteins.
Osmosis
Movement of water across a selectively permeable membrane from an area of high water potential to an area of low water potential.
Tonicity
The measure of osmotic pressure gradient between two solutions separated by a selectively permeable membrane.
Active Transport
Movement of molecules against a concentration gradient with the use of energy.
Endocytosis
The process by which the cell membrane engulfs large molecules or particles to form a vacuole or vesicle.