openstax notes

Biology

The scientific study of life and living organisms, ranging from microscopic cellular components to entire ecosystems.

Scientific Method

A structured method of research with defined steps that include careful observation, forming testable hypotheses, and conducting repeatable experiments.

Hypothesis

A suggested, testable, and falsifiable explanation for an observed event or natural phenomenon.

Scientific Theory

A thoroughly tested and confirmed explanation for observations or phenomena that is supported by a large body of evidence.

Inductive Reasoning

A form of logical thinking that uses related specific observations to arrive at a general conclusion.

Deductive Reasoning

A form of logical thinking that uses a general principle or law to predict specific results.

Basic Science

Scientific inquiry aimed at expanding knowledge and understanding fundamental principles, regardless of short-term practical application.

Applied Science

A field of science that aims to use scientific knowledge to solve specific, practical real-world problems.

Homeostasis

The process by which living organisms maintain a relatively stable internal environment required to sustain life.

Three Domains of Life

The biological classifications of Archaea, Bacteria, and Eukarya.

Atomic Number

The total number of protons in an atom's nucleus, which identifies the specific element.

Mass Number

The total count of protons and neutrons within an atom's nucleus.

Isotopes

Different forms of the same chemical element that possess the same number of protons but a different number of neutrons.

Valence Shell

The outermost electron shell of an atom, which governs its energetic stability and chemical reactivity.

Octet Rule

The principle stating that atoms are most energetically stable when their valence shell contains eight electrons (excluding the innermost shell, which holds two).

Cation

A positively charged ion formed when a neutral atom loses one or more electrons.

Anion

A negatively charged ion formed when a neutral atom gains one or more electrons.

Ionic Bond

A chemical bond formed by the electrostatic attraction between oppositely charged ions resulting from electron transfer.

Covalent Bond

A strong chemical bond formed when two atoms share one or more pairs of valence electrons.

Polar Covalent Bond

A covalent bond in which shared electrons are pulled closer to the more electronegative atom, creating partial negative ($\delta^-$) and partial positive ($\delta^+$) charges.

Hydrophilic

A characteristic of polar or charged substances that readily interact with or dissolve in water.

Hydrophobic

A characteristic of nonpolar molecules that do not interact well with water and tend to repel it.

Specific Heat Capacity

The amount of heat energy required to change the temperature of one gram of a substance by one degree Celsius ($1,^\circ\text{C}$).

Heat of Vaporization

The amount of heat energy required to convert one gram of a liquid substance into a gas.

Cohesion

The intermolecular attraction between like molecules, such as hydrogen bonding holding water molecules together.

Adhesion

The attraction between different types of molecules, such as water molecules clinging to charged capillary surfaces.

Buffer

A substance or solution that absorbs excess $\text{H}^+$ or $\text{OH}^-$ ions to resist drastic changes in pH.

Isomers

Molecules that share the same chemical formula but differ in the arrangement or structural placement of their atoms.

Enantiomers

Molecules that have the same chemical structure and bonds but are non-superimposable mirror images of each other.

Dehydration Synthesis

A chemical reaction in which two monomers combine via a covalent bond, releasing a water molecule as a byproduct.

Hydrolysis

A chemical reaction that breaks a covalent bond in a polymer by adding a split water molecule ($\text{H}^+$ and $\text{OH}^-$).

Monosaccharides

The simplest monomeric units of carbohydrates, consisting of simple sugars with three to seven carbon atoms.

Glycosidic Bond

A covalent bond formed between a carbohydrate molecule and another molecule, such as two monosaccharides joining to form a disaccharide.

Glycogen

A highly branched polysaccharide composed of glucose monomers that serves as the primary energy storage molecule in animals.

Cellulose

A structural polysaccharide consisting of glucose monomers linked by $\beta\text{ 1-4}$ glycosidic bonds, forming the cell walls of plants.

Triglyceride

A lipid molecule composed of three fatty acid chains linked to a glycerol backbone via ester bonds.

Phospholipid

An amphipathic lipid consisting of two fatty acid tails and a modified phosphate group attached to a glycerol backbone.

Peptide Bond

The covalent bond that connects the carboxyl group of one amino acid to the amino group of another through dehydration synthesis.

Primary Structure of a Protein

The specific linear sequence of amino acids in a polypeptide chain.

Secondary Structure of a Protein

Localized folding patterns within a polypeptide chain held together by hydrogen bonds, most commonly forming $\alpha\text{-helices}$ and $\beta\text{-pleated sheets}$.

Tertiary Structure of a Protein

The unique overall three-dimensional shape of a single polypeptide chain, determined by chemical interactions among amino acid R-groups.

Denaturation

The loss of a protein's three-dimensional shape and function caused by changes in temperature, pH, or exposure to chemicals, without breaking its primary structure.

Nucleotide

The fundamental monomer of nucleic acids, comprising a nitrogenous base, a pentose sugar, and one or more phosphate groups.

Phosphodiester Linkage

The covalent bond that links the $5'$ phosphate group of one nucleotide to the $3'$ hydroxyl group of the adjacent nucleotide in a nucleic acid strand.