AP Biology Ultimate Guide

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.

Bulk Flow

The one-way movement of fluids brought about by pressure.

Bioenergetics

The study of how cells obtain and use energy.

Thermodynamics

The study of energy transformation.

Enzyme

A biological catalyst that speeds up reactions by lowering the activation energy.

Enzyme Specificity

The ability of an enzyme to catalyze only one kind of reaction.

Enzyme-Substrate Complex

The temporary binding of an enzyme to one or more substrates.

Induced-fit

The change in shape of an enzyme to accommodate the shape of its substrate.

Enzyme Regulation

The control of enzymatic activity by regulating the conditions that influence the shape of the enzyme.

ATP

Adenosine triphosphate, a molecule that stores and releases energy.

Cellular Respiration

The process of breaking down sugar to make ATP.

Photosynthesis

The process by which light energy is converted to chemical energy.

Calvin-Benson Cycle

The dark reactions that use ATP and NADPH produced in the light reactions to convert CO2 into carbohydrates in the stroma of the leaf.

Temporal Separation

A strategy used by CAM plants to separate carbon fixation and the Calvin cycle by incorporating CO2 into organic acids at night and releasing it during the day.

Carbon Fixation

A process used by C4 plants to fix CO2 in a different part of the leaf from the Calvin cycle, preventing photorespiration and producing a four-carbon molecule as the first product.

Electron Transport Chain

The final stage of aerobic respiration where electrons from NADH and FADH2 are transported through a series of proteins to create a proton gradient that powers ATP synthesis.

Pyruvic Acid

The three-carbon molecule produced by the splitting of glucose in the first stage of glycolysis, which also results in the net production of two ATP and two NADH molecules.

Cell communication

The process by which cells of multi-celled organisms coordinate their activities by communicating with one another through cell-to-cell contact or cell signaling.

Long-range signaling

A type of cell signaling that affects cells throughout the organism, often done through signaling molecules called ligands that bind to receptors and trigger a response by changing the shape of the receptor protein.

Signal transduction

The process by which an external signal is transmitted to the inside of a cell, usually involving three steps: a signaling molecule binding to a specific receptor, activation of a signal transduction pathway, and production of a cellular response.

Plasma membrane receptor

An integral membrane protein that transmits signals from the extracellular space into the cytoplasm, binding a particular molecule in a highly specific way. It is required for signaling molecules that cannot enter the cell.

Ligand-gated ion channels

Membrane receptors that open or close an ion channel upon binding a particular ligand.

Catalytic (enzyme-linked) receptors

Membrane receptors that have an enzymatic active site on the cytoplasmic side of the membrane and are initiated by ligand binding at the extracellular surface.

G-protein-linked receptor

Membrane receptors that bind a different version of a G-protein on the intracellular side when a ligand is bound extracellularly, causing activation of secondary messengers within the cell.

Signal transduction cascades

Processes that amplify a signal in a cell.

Homeostasis

The set of conditions under which living things can successfully survive.

Negative feedback pathway

A feedback pathway that works by turning itself off using the end product of the pathway.

Positive feedback pathway

A feedback pathway that involves an end product playing a role and further stimulating the pathway instead of inhibiting it.

Cell Cycle

The period from the beginning of one cell division to the beginning of the next, divided into two periods: interphase and mitosis.

Interphase

The growing phase of the cell cycle, divided into three stages: G1, S, G2. The S phase is the most important phase, where the cell replicates its genetic material.

Sister Chromatids

Identical strands of DNA that are duplicated during interphase and held together by a structure called the centromere.

Cell Cycle Checkpoints

Control mechanisms that ensure proper cell division is happening in eukaryotic cells, regulated by proteins called cyclins and cyclin-dependent kinases (CDKs).

Oncogenes

Mutated genes that can convert normal cells into cancerous cells, while tumour suppressor genes produce proteins that prevent the conversion of normal cells into cancer cells.

Mitosis

The process of cellular division, occurring in four stages: prophase, metaphase, anaphase, and telophase.

Chromatin

Genetic material in its decondensed state, occurring during interphase once daughter cells are produced and the cell goes back to its original state.

Purpose of Mitosis

Achieving the production of identical daughter cells and maintaining the proper number of chromosomes from generation to generation, for growth, repair, or asexual reproduction.

Gregor Mendel

The monk who discovered genetics and is known as the father of genetics.