Cellular Metabolism, Thermodynamics, Cell Division, and DNA Replication

A complete set of vocabulary flashcards based on the lecture material, detailing key terms across metabolism, bioenergetics, enzymes, thermodynamics, cell division, and DNA replication.

Metabolism

All of the chemical reactions that transpire inside cells, including those that use and release energy.

Anabolic Pathways

Metabolic pathways that require an input of energy to synthesize complex molecules from simpler ones.

Catabolic Pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler ones.

Bioenergetics

The term used by scientists to discuss the concept of energy flow through living systems, such as cells.

Adenosine Triphosphate (ATP)

A high-energy molecule consisting of an adenosine backbone bound to three phosphate groups, functioning as the primary energy currency of all cells.

Gibbs Free Energy ($G$)

The amount of usable energy available to perform work in a system at constant temperature and pressure, after accounting for entropy.

Exergonic Reactions

Chemical reactions that release free energy, have a negative change in free energy ($\Delta G < 0$), and occur spontaneously.

Endergonic Reactions

Chemical reactions that require an input of energy, have a positive change in free energy ($\Delta G > 0$), and are non-spontaneous.

Activation Energy ($E_A$)

The initial small amount of energy input required for all chemical reactions to proceed with their steps.

Transition State

A high-energy, unstable, contorted state that reactant molecules must achieve before a chemical reaction can proceed.

First Law of Thermodynamics

The physical law stating that the total amount of energy in the universe is constant, meaning energy cannot be created or destroyed, only transferred or transformed.

Second Law of Thermodynamics

The physical law stating that every energy transfer or transformation increases the total entropy of the universe because some energy is lost in an unusable form, such as heat.

Entropy

A thermodynamic measure of randomness or disorder within a physical system.

Enzymes

Biological catalysts, usually proteins, that speed up chemical reactions by lowering their activation energy without altering the reaction's overall change in free energy ($\Delta G$).

Active Site

The specific region within an enzyme where substrate molecules bind and where the chemical reaction takes place.

Induced Fit

A dynamic model of enzyme-substrate interaction where both enzyme and substrate undergo conformational shifts upon binding to optimize the fit for the transition state.

Competitive Inhibition

A mechanism of enzyme regulation in which an inhibitor molecule competes directly with the substrate for binding to the active site.

Noncompetitive Inhibition

A mechanism of enzyme regulation in which an inhibitor molecule binds to an allosteric site on an enzyme, preventing substrate binding or reducing catalytic activity.

Feedback Inhibition

A cellular control mechanism in which the end product of a metabolic pathway inhibits an upstream enzyme in that same pathway to prevent overproduction.

Substrate-Level Phosphorylation

The direct transfer of a phosphate group from a phosphorylated intermediate reactant molecule to ADP to generate ATP.

Oxidative Phosphorylation

The production of ATP using the energy derived from the electron transport chain and chemiosmosis in mitochondria or plasma membranes.

Glycolysis

An anaerobic metabolic pathway occurring in the cytoplasm that breaks down one glucose molecule into two pyruvate molecules, yielding a net gain of $2\,mols$ of ATP and $2\,mols$ of NADH.

Chemiosmosis

The process of ATP synthesis powered by the movement of hydrogen ions (protons) diffusing down their electrochemical gradient through ATP synthase.

Fermentation

An anaerobic process that uses an organic molecule as the final electron acceptor to regenerate $\text{NAD}^+$ from $\text{NADH}$ so glycolysis can continue.

Homologous Chromosomes

Matched pairs of chromosomes in diploid organisms that are the same length and carry genes for the same traits at identical loci, inherited from different biological parents.

Sister Chromatids

Identical copies of a single replicated chromosome bound together by cohesin proteins at the centromere.

Nucleosome

The basic unit of eukaryotic chromatin packaging, consisting of short stretches of double-stranded DNA wrapped around a core of eight histone proteins.

Binary Fission

The prokaryotic cell division process that replicates a single circular chromosome and partitions the cell into two genetically identical daughter cells.

FtsZ

A prokaryotic protein homologous to eukaryotic tubulin that assembles into a ring at the midpoint of an elongating bacterial cell to direct septum formation during binary fission.

Interphase

The preparatory period of the eukaryotic cell cycle comprising $G_1$, $S$, and $G_2$ phases, during which the cell grows, performs normal functions, and replicates its DNA.

Cleavage Furrow

The fissure formed during animal cell cytokinesis as a contractile ring of actin filaments pulls the cell equator inward.

Cell Plate

A vesicular structure formed by fused Golgi vesicles at the metaphase plate in dividing plant cells that develops into a new cell wall.

p53

A multi-functional negative regulatory protein that monitors genomic DNA integrity at the $G_1$ checkpoint and can trigger DNA repair or programmed cell death (apoptosis).

Proto-oncogenes

Normal genes coding for positive cell-cycle regulators that can become cancer-causing oncogenes when mutated to be overactive.

Tumor Suppressor Genes

Segments of DNA coding for negative cell-cycle regulatory proteins that prevent uncontrolled cell division.

Chargaff's Rules

The empirical observation that in any species' DNA, the concentration of adenine equals thymine ($A = T$) and guanine equals cytosine ($G = C$).

Phosphodiester Bond

The covalent linkage formed between the $5'$ phosphate group of one nucleotide sugar and the $3'\text{-OH}$ group of the adjacent nucleotide sugar in a nucleic acid strand.

Semi-Conservative Replication

The mechanism of DNA replication in which each parental strand acts as a template, producing two daughter DNA molecules containing one original strand and one new strand.

Okazaki Fragments

Short segments of DNA synthesized on the lagging strand away from the replication fork, each requiring a separate RNA primer.

Telomeres

Repetitive, non-coding DNA sequences located at the ends of linear eukaryotic chromosomes that protect coding genes from being lost during replication.

Nucleotide Excision Repair

A DNA repair mechanism that recognizes damaged bases (such as UV-induced pyrimidine dimers), cuts the damaged strand on both sides, and resynthesizes the excised segment.