Gene Expression

Miller-Urey Experiment

An experiment that simulated early Earth conditions and demonstrated how organic molecules like amino acids could form from inorganic precursors.

Octet Rule

The principle that atoms are most stable when their outer electron shell contains eight electrons, influencing covalent bond formation.

Electronegativity

The ability of an atom to attract electrons in a chemical bond, affecting whether a bond is polar or nonpolar.

Ionic Bond

A chemical bond formed through the electrostatic attraction between oppositely charged ions.

Hydrogen Bond

A weak attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Hydrophobic Interaction

The clustering of nonpolar molecules in an aqueous environment to minimize their contact with water.

Water's Structure

Water's polar structure and ability to form hydrogen bonds contribute to its unique properties like high heat capacity and solvent abilities.

Acid

A substance that releases hydrogen ions (H+) in solution.

Base

A substance that accepts hydrogen ions (H+) in solution.

pH Scale

A scale measuring the acidity or basicity of a solution based on hydrogen ion concentration.

Carbon's Unique Properties

Carbon's ability to form four covalent bonds makes it versatile for constructing complex organic molecules.

Macromolecules

The four main categories of macromolecules are proteins, nucleic acids, carbohydrates, and lipids, each with distinct monomers.

Saturated Fatty Acids

Fatty acids without double bonds, typically solid at room temperature due to tight packing.

Unsaturated Fatty Acids

Fatty acids with one or more double bonds, making them liquid at room temperature.

Primary Structure of Protein

The linear sequence of amino acids in a polypeptide chain.

Secondary Structure of Protein

Local folding patterns of a polypeptide chain, like α-helices and β-sheets, stabilized by hydrogen bonds.

Tertiary Structure of Protein

The overall three-dimensional conformation of a polypeptide, stabilized by various noncovalent interactions.

Quaternary Structure of Protein

The arrangement of multiple polypeptide subunits in a protein complex.

Protocells

Hypothetical early cell-like structures thought to precede the first living cells.

Covalent Bond

A strong bond formed by the sharing of electrons between atoms.

Valence Electrons

Electrons in the outermost shell responsible for chemical bonding.

Polar Molecule

A molecule with an uneven distribution of charge, resulting in partial positive and negative regions.

Nonpolar Molecule

A molecule with an even distribution of charge, leading to equal sharing of electrons.

Peptide Bond

A covalent bond linking two amino acids during protein synthesis.

Amphipathic Molecule

A molecule that has both hydrophilic (water-attracting) and hydrophobic (water-repelling) properties.

Redistribution of energy

Energy changes during reactions that align with the first law of thermodynamics.

Entropy

A measure of disorder or randomness within a system, increasing according to the second law of thermodynamics.

Equilibrium Constant (Keq)

A value that determines the ratio of products to reactants at equilibrium.

ATP Hydrolysis

The process of breaking down ATP to release energy used for cellular reactions.

Steady-State System

A dynamic state in which the concentrations of reactants and products remain constant.

Enzyme

A biological catalyst that accelerates chemical reactions by lowering activation energy.

Active Site

The specific region on an enzyme where substrate binding and catalysis occur.

Activation Energy (EA)

The energy barrier that must be overcome for a chemical reaction to proceed.

Competitive Inhibition

A type of inhibition where the inhibitor competes with the substrate for the active site.

Noncompetitive Inhibition

An inhibition mechanism in which the inhibitor binds to an enzyme at a site other than the active site.

Free Energy (ΔG)

The portion of energy in a system that can perform work; negative ΔG signifies spontaneity.

Transition State

An unstable state in a reaction where reactants have sufficient energy to form products.

Bioenergetics

The study of how energy flows through living systems.

Catalyst

A substance that speeds up a chemical reaction without being consumed.

Coenzyme

An organic non-protein molecule that assists enzymes by providing chemical groups.

Cofactor

An inorganic compound that enhances enzyme activity.

Endergonic Reaction

A reaction requiring input energy, resulting in a positive ΔG.

Exergonic Reaction

A spontaneous reaction that releases energy, indicated by negative ΔG.

Michaelis Constant (KM)

The substrate concentration at which an enzyme operates at half its maximum velocity.

Substrate

The substance an enzyme acts upon during a chemical reaction.

Turnover Number (kcat)

The maximum number of substrate molecules converted to product per enzyme molecule per minute.

Denaturation

The process in which a protein loses its structure and function due to external stress.

Chaperonin

A protein complex that assists in properly folding other proteins.

Nucleotide

The fundamental building block of nucleic acids consisting of a sugar, phosphate group, and nitrogenous base.

Purine

A double-ring nitrogenous base in nucleotides, such as adenine and guanine.

Pyrimidine

A single-ring nitrogenous base in nucleotides, such as cytosine, thymine, and uracil.

Phosphodiester Bond

A covalent bond linking nucleotides in a nucleic acid.

Ribozyme

An RNA molecule capable of acting as an enzyme.

Triacylglycerol

A lipid made of three fatty acids linked to a glycerol backbone.

Steroid

A type of lipid characterized by a four-ring structure, such as cholesterol.

Phospholipid

A lipid containing hydrophilic heads and hydrophobic tails, essential for cell membranes.

Fibrous Protein

Structural proteins that are elongated and insoluble, like collagen.

Globular Protein

Proteins that are compact and soluble, serving as enzymes or transporters.

Conformational Changes

Alterations in the three-dimensional structure of proteins.

Protein Domain

A distinct functional region within a protein, often exhibiting independent stability.

Post Translational Modification (PTM)

Chemical changes of proteins after synthesis, influencing function and activity.

Alpha (α) Helix

A common secondary structure of proteins characterized by coiling.

Beta (β) Sheet

A secondary structure formed by hydrogen bonds between adjacent polypeptide chains.

Hydrophilic

Substances that have an affinity for water; often polar.

Hydrophobic

Substances that repel water; typically nonpolar.

Fatty Acid

A long-chain hydrocarbon with a carboxyl group, serving as building blocks of lipids.