Biology Key Concepts and Vocabulary

Vocabulary flashcards generated from the biological foundational concepts, thermodynamics, nucleic acids, and protein structure lecture notes.

Hypothesis

A tentative, testable explanation for a phenomenon or a proposed answer to a research question.

Theory

A well-tested and widely accepted scientific explanation for a natural phenomenon that is supported by a large body of evidence.

Control Group

A baseline sample or test subject in an experiment that does not receive the experimental treatment, serving as a standard for comparison.

Independent Variable

The specific factor that a researcher deliberately changes or manipulates in an experiment to test its effect on a living system.

Dependent Variable

The factor that you measure or observe to see how it responds to changes in an experiment.

Null Hypothesis

An expected result of an experiment.

Central Dogma (of Biology)

The theory that genetic information flows in one direction: from DNA to RNA, and then to proteins.

ATP/adenosine triphosphate

Adenosine triphosphate, which is the primary molecule used to store and transfer energy in all living cells. It is often called the "energy currency" of the cell.

Phylogenetic Tree

A branching diagram that shows the evolutionary history and relationships among different species or groups of organisms.

Eukaryotic Cell

A complex cell that contains a distinct, membrane-bound nucleus and other specialized, membrane-bound parts called organelles.

Prokaryotic Cell

Simple cell.

Covalent Bond

Two molecules share a pair of electrons.

Ionic Bond

A molecule transfers a pair of electrons to another.

Hydrogen Bond

A weak interaction between two molecules or different parts of the same molecule resulting from the attraction between a hydrogen atom with a partial positive charge and another atom (usually O or N) with a partial negative charge.

Polar

Bond has net positive charge on one side and a negative charge on the other side.

Nonpolar

Bond has no charge.

Hydrophilic

Interacts well with water.

Hydrophobic

Doesn’t interact with water.

Monomer

A small molecule that can covalently bind to other similar molecules to form a larger macromolecule.

Polymer

Any large molecule composed of small repeating units (monomers) bonded together. The main biological polymers are proteins, nucleic acids, and polysaccharides.

Entropy

A quantitative measure of the amount of disorder of any system, such as a group of molecules.

Gibbs Free Energy

The amount of energy available to work.

Enzyme

A protein catalyst used by living organisms to increase the rate of biological reactions.

Activation Energy

The energy required to make reactants into products.

Endergonic Reaction/Non-spontaneous

Energy is absorbed in chemical reaction (Gibbs is positive).

Exergonic Reaction/Spontaneous

Outputs energy (Gibbs free energy is negative).

Endothermic Reaction

A chemical reaction that absorbs heat.

Exothermic Reaction

Chemical reaction that releases heat.

Peptide

The covalent bond formed by a condensation reaction between two amino acids.

Protein

A macromolecule consisting of one or more polypeptide chains. Each polypeptide has a unique sequence of amino acids and each protein generally possesses a characteristic three-dimensional shape.

Peptide Bond

The covalent bond formed by a condensation reaction between two amino acids.

RNA World Hypothesis

Proposal that at a particular stage in the evolution of life, RNA both stored genetic information and catalyzed its own replication and that RNA emerged before DNA and proteins during chemical evolution.

Nucleotide

A molecule consisting of a five-carbon sugar (ribose or deoxyribose), one or more phosphate groups, and one of several nitrogen-containing bases. Equivalent to a nucleoside plus one or more phosphate groups.

Nucleic Acid

A macromolecule composed of nucleotide monomers. Generally used by cells to store or transmit hereditary information. Includes ribonucleic acid and deoxyribonucleic acid.

Purine

A class of double-ringed nitrogenous bases [adenine (A), guanine (G)] found in nucleotides.

Pyrimidine

A class of single-ringed nitrogenous bases [cytosine (C), uracil (U), thymine (T)] found in nucleotides.

Ribose

A simple five-carbon sugar found in all living cells that acts as an essential building block for genetic material and cellular energy.

Deoxyribose

A five-carbon sugar molecule that forms the stable structural backbone of DNA.

Double Helix

Two complementary strands of DNA wound together in a double helix loop.

One Gene One Enzyme (protein) Hypothesis

Each gene directs the formation of a single, specific enzyme that controls a specific step in a metabolic pathway.

Degenerate

Different structural components can perform the same function or produce the same output.

Transcription

The first step of gene expression, where an enzyme called RNA polymerase copies a DNA sequence of a gene to make an RNA molecule.

Primary Protein Structure

The sequence of amino acid residues in a protein polymer; also the sequence of nucleotides in a single nucleic acid strand.

Secondary Protein Structure

In proteins, localized folding of a polypeptide chain into regular structures (i.e., alpha-helices and beta-pleated sheets) stabilized by hydrogen bonding between atoms of the peptide backbone. In nucleic acids, elements of structure (e.g., helices and hairpins) stabilized by hydrogen bonding between complementary bases and hydrophobic interactions with the aqueous environment.

Tertiary Protein Structure

The overall three-dimensional shape of a single polypeptide chain, resulting from multiple interactions among the amino acid side chains and the peptide backbone. In nucleic acids, three-dimensional shape is formed by hydrogen bonding between complementary bases and other interactions.

Quaternary Protein Structure

In proteins, the overall three-dimensional shape formed from the combination of two or more polypeptide chains (subunits); determined by the number, relative positions, and interactions of the subunits. In nucleic acids, two or more distinct single strands will form this level of structure through hydrogen bonding between complementary bases and hydrophobic interactions with the aqueous environment.