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Key Terms

  • Page ID
    19312
  • active transport
    form of transport across the cell membrane that requires input of cellular energy
    amphipathic
    describes a molecule that exhibits a difference in polarity between its two ends, resulting in a difference in water solubility
    anaphase
    third stage of mitosis (and meiosis), during which sister chromatids separate into two new nuclear regions of a dividing cell
    anticodon
    consecutive sequence of three nucleotides on a tRNA molecule that is complementary to a specific codon on an mRNA molecule
    autolysis
    breakdown of cells by their own enzymatic action
    autophagy
    lysosomal breakdown of a cell’s own components
    cell cycle
    life cycle of a single cell, from its birth until its division into two new daughter cells
    cell membrane
    membrane surrounding all animal cells, composed of a lipid bilayer interspersed with various molecules; also known as plasma membrane
    centriole
    small, self-replicating organelle that provides the origin for microtubule growth and moves DNA during cell division
    centromere
    region of attachment for two sister chromatids
    centrosome
    cellular structure that organizes microtubules during cell division
    channel protein
    membrane-spanning protein that has an inner pore which allows the passage of one or more substances
    checkpoint
    progress point in the cell cycle during which certain conditions must be met in order for the cell to proceed to a subsequence phase
    chromatin
    substance consisting of DNA and associated proteins
    chromosome
    condensed version of chromatin
    cilia
    small appendage on certain cells formed by microtubules and modified for movement of materials across the cellular surface
    cleavage furrow
    contractile ring that forms around a cell during cytokinesis that pinches the cell into two halves
    codon
    consecutive sequence of three nucleotides on an mRNA molecule that corresponds to a specific amino acid
    concentration gradient
    difference in the concentration of a substance between two regions
    cyclin
    one of a group of proteins that function in the progression of the cell cycle
    cyclin-dependent kinase (CDK)
    one of a group of enzymes associated with cyclins that help them perform their functions
    cytokinesis
    final stage in cell division, where the cytoplasm divides to form two separate daughter cells
    cytoplasm
    internal material between the cell membrane and nucleus of a cell, mainly consisting of a water-based fluid called cytosol, within which are all the other organelles and cellular solute and suspended materials
    cytoskeleton
    “skeleton” of a cell; formed by rod-like proteins that support the cell’s shape and provide, among other functions, locomotive abilities
    cytosol
    clear, semi-fluid medium of the cytoplasm, made up mostly of water
    diffusion
    movement of a substance from an area of higher concentration to one of lower concentration
    diploid
    condition marked by the presence of a double complement of genetic material (two sets of chromosomes, one set inherited from each of two parents)
    DNA polymerase
    enzyme that functions in adding new nucleotides to a growing strand of DNA during DNA replication
    DNA replication
    process of duplicating a molecule of DNA
    electrical gradient
    difference in the electrical charge (potential) between two regions
    endocytosis
    import of material into the cell by formation of a membrane-bound vesicle
    endoplasmic reticulum (ER)
    cellular organelle that consists of interconnected membrane-bound tubules, which may or may not be associated with ribosomes (rough type or smooth type, respectively)
    exocytosis
    export of a substance out of a cell by formation of a membrane-bound vesicle
    exon
    one of the coding regions of an mRNA molecule that remain after splicing
    extracellular fluid (ECF)
    fluid exterior to cells; includes the interstitial fluid, blood plasma, and fluid found in other reservoirs in the body
    facilitated diffusion
    diffusion of a substance with the aid of a membrane protein
    flagellum
    appendage on certain cells formed by microtubules and modified for movement
    G0 phase
    phase of the cell cycle, usually entered from the G1 phase; characterized by long or permanent periods where the cell does not move forward into the DNA synthesis phase
    G1 phase
    first phase of the cell cycle, after a new cell is born
    G2 phase
    third phase of the cell cycle, after the DNA synthesis phase
    gene
    functional length of DNA that provides the genetic information necessary to build a protein
    gene expression
    active interpretation of the information coded in a gene to produce a functional gene product
    genome
    entire complement of an organism’s DNA; found within virtually every cell
    glycocalyx
    coating of sugar molecules that surrounds the cell membrane
    glycoprotein
    protein that has one or more carbohydrates attached
    Golgi apparatus
    cellular organelle formed by a series of flattened, membrane-bound sacs that functions in protein modification, tagging, packaging, and transport
    helicase
    enzyme that functions to separate the two DNA strands of a double helix during DNA replication
    histone
    family of proteins that associate with DNA in the nucleus to form chromatin
    homologous
    describes two copies of the same chromosome (not identical), one inherited from each parent
    hydrophilic
    describes a substance or structure attracted to water
    hydrophobic
    describes a substance or structure repelled by water
    hypertonic
    describes a solution concentration that is higher than a reference concentration
    hypotonic
    describes a solution concentration that is lower than a reference concentration
    integral protein
    membrane-associated protein that spans the entire width of the lipid bilayer
    intermediate filament
    type of cytoskeletal filament made of keratin, characterized by an intermediate thickness, and playing a role in resisting cellular tension
    interphase
    entire life cycle of a cell, excluding mitosis
    interstitial fluid (IF)
    fluid in the small spaces between cells not contained within blood vessels
    intracellular fluid (ICF)
    fluid in the cytosol of cells
    intron
    non-coding regions of a pre-mRNA transcript that may be removed during splicing
    isotonic
    describes a solution concentration that is the same as a reference concentration
    kinetochore
    region of a centromere where microtubules attach to a pair of sister chromatids
    ligand
    molecule that binds with specificity to a specific receptor molecule
    lysosome
    membrane-bound cellular organelle originating from the Golgi apparatus and containing digestive enzymes
    messenger RNA (mRNA)
    nucleotide molecule that serves as an intermediate in the genetic code between DNA and protein
    metaphase
    second stage of mitosis (and meiosis), characterized by the linear alignment of sister chromatids in the center of the cell
    metaphase plate
    linear alignment of sister chromatids in the center of the cell, which takes place during metaphase
    microfilament
    the thinnest of the cytoskeletal filaments; composed of actin subunits that function in muscle contraction and cellular structural support
    microtubule
    the thickest of the cytoskeletal filaments, composed of tubulin subunits that function in cellular movement and structural support
    mitochondrion
    one of the cellular organelles bound by a double lipid bilayer that function primarily in the production of cellular energy (ATP)
    mitosis
    division of genetic material, during which the cell nucleus breaks down and two new, fully functional, nuclei are formed
    mitotic phase
    phase of the cell cycle in which a cell undergoes mitosis
    mitotic spindle
    network of microtubules, originating from centrioles, that arranges and pulls apart chromosomes during mitosis
    multipotent
    describes the condition of being able to differentiate into different types of cells within a given cell lineage or small number of lineages, such as a red blood cell or white blood cell
    mutation
    change in the nucleotide sequence in a gene within a cell’s DNA
    nuclear envelope
    membrane that surrounds the nucleus; consisting of a double lipid-bilayer
    nuclear pore
    one of the small, protein-lined openings found scattered throughout the nuclear envelope
    nucleolus
    small region of the nucleus that functions in ribosome synthesis
    nucleosome
    unit of chromatin consisting of a DNA strand wrapped around histone proteins
    nucleus
    cell’s central organelle; contains the cell’s DNA
    oligopotent
    describes the condition of being more specialized than multipotency; the condition of being able to differentiate into one of a few possible cell types
    organelle
    any of several different types of membrane-enclosed specialized structures in the cell that perform specific functions for the cell
    osmosis
    diffusion of water molecules down their concentration gradient across a selectively permeable membrane
    passive transport
    form of transport across the cell membrane that does not require input of cellular energy
    peripheral protein
    membrane-associated protein that does not span the width of the lipid bilayer, but is attached peripherally to integral proteins, membrane lipids, or other components of the membrane
    peroxisome
    membrane-bound organelle that contains enzymes primarily responsible for detoxifying harmful substances
    phagocytosis
    endocytosis of large particles
    pinocytosis
    endocytosis of fluid
    pluripotent
    describes the condition of being able to differentiate into a large variety of cell types
    polypeptide
    chain of amino acids linked by peptide bonds
    polyribosome
    simultaneous translation of a single mRNA transcript by multiple ribosomes
    promoter
    region of DNA that signals transcription to begin at that site within the gene
    prophase
    first stage of mitosis (and meiosis), characterized by breakdown of the nuclear envelope and condensing of the chromatin to form chromosomes
    proteome
    full complement of proteins produced by a cell (determined by the cell’s specific gene expression)
    reactive oxygen species (ROS)
    a group of extremely reactive peroxides and oxygen-containing radicals that may contribute to cellular damage
    receptor
    protein molecule that contains a binding site for another specific molecule (called a ligand)
    receptor-mediated endocytosis
    endocytosis of ligands attached to membrane-bound receptors
    ribosomal RNA (rRNA)
    RNA that makes up the subunits of a ribosome
    ribosome
    cellular organelle that functions in protein synthesis
    RNA polymerase
    enzyme that unwinds DNA and then adds new nucleotides to a growing strand of RNA for the transcription phase of protein synthesis
    S phase
    stage of the cell cycle during which DNA replication occurs
    selective permeability
    feature of any barrier that allows certain substances to cross but excludes others
    sister chromatid
    one of a pair of identical chromosomes, formed during DNA replication
    sodium-potassium pump
    (also, Na+/K+ ATP-ase) membrane-embedded protein pump that uses ATP to move Na+ out of a cell and K+ into the cell
    somatic cell
    all cells of the body excluding gamete cells
    spliceosome
    complex of enzymes that serves to splice out the introns of a pre-mRNA transcript
    splicing
    the process of modifying a pre-mRNA transcript by removing certain, typically non-coding, regions
    stem cell
    cell that is oligo-, multi-, or pleuripotent that has the ability to produce additional stem cells rather than becoming further specialized
    telophase
    final stage of mitosis (and meiosis), preceding cytokinesis, characterized by the formation of two new daughter nuclei
    totipotent
    embryonic cells that have the ability to differentiate into any type of cell and organ in the body
    transcription
    process of producing an mRNA molecule that is complementary to a particular gene of DNA
    transcription factor
    one of the proteins that regulate the transcription of genes
    transfer RNA (tRNA)
    molecules of RNA that serve to bring amino acids to a growing polypeptide strand and properly place them into the sequence
    translation
    process of producing a protein from the nucleotide sequence code of an mRNA transcript
    triplet
    consecutive sequence of three nucleotides on a DNA molecule that, when transcribed into an mRNA codon, corresponds to a particular amino acid
    unipotent
    describes the condition of being committed to a single specialized cell type
    vesicle
    membrane-bound structure that contains materials within or outside of the cell
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