Chapter 3 – Organelles, Cell Structure, and Cell Cycle

Vocabulary flashcards covering major organelles, cellular structures, molecular processes, and phases of the cell cycle discussed in Chapter 3.

Cytoplasm

The collective name for a cell’s cytosol plus all of its organelles.

Cytosol

Jelly-like fluid portion of the cytoplasm; medium for biochemical reactions.

Organelle

“Little organ” – specialized intracellular structure that performs a unique function.

Membranous organelle

Organelle surrounded by its own lipid bilayer membrane (e.g., mitochondrion, Golgi).

Non-membranous organelle

Organelle lacking a surrounding membrane (e.g., cytoskeletal filaments, centrosome).

Endomembrane system

ER, Golgi apparatus, and vesicles that produce, package, and export cellular products.

Endoplasmic reticulum (ER)

Network of membrane channels continuous with the nuclear envelope; transports, synthesizes, and stores materials.

Rough ER (RER)

ER studded with ribosomes; site of protein synthesis and modification for membrane or export.

Smooth ER (SER)

ER without ribosomes; synthesizes lipids/steroids, stores Ca²⁺, metabolizes carbs, and detoxifies toxins.

Golgi apparatus

Stacked membranes that sort, modify, and ship products from the RER; also forms lysosomes.

Vesicle

Small membrane-bound sac used to transport or store substances in the cell.

Lysosome

Vesicle containing digestive enzymes that break down nutrients, defective proteins, or bacteria for recycling.

Peroxisome

Specialized lysosome rich in oxidative enzymes; detoxifies harmful chemicals, abundant in liver cells.

Ribosome

Organelle made of rRNA and proteins; site of translation (protein synthesis); free or ER-bound.

Mitochondrion

Bean-shaped, double-membrane organelle that transforms energy to ATP; numerous in muscle and neurons.

Cytoskeleton

Network of fibrous proteins providing structural support, motility, reproduction, and intracellular transport.

Microtubule

Dynamic, tubulin-based cytoskeletal filament; forms cilia/flagella, spindle fibers, and transport tracks.

Intermediate filament

Relatively static cytoskeletal fiber of varied proteins (e.g., keratin) that stabilizes cell shape.

Microfilament

Dynamic actin (and some myosin) filament involved in cell crawling, contraction, and microvilli support.

Centrosome

Region near nucleus containing a pair of centrioles; microtubule-organizing center.

Centriole

One of two short microtubule cylinders in the centrosome; helps form spindle or cilia/flagella.

Microvilli

Fingerlike membrane projections that increase surface area, especially in small-intestine epithelium.

Cilia

Short, numerous motile extensions that beat rhythmically to move substances along cell surfaces.

Flagellum

Longer appendage specialized for locomotion; in humans, present only on sperm cells.

Nucleus

Cell control center housing DNA instructions for protein synthesis; may be absent (RBC) or multiple (muscle).

Nuclear envelope

Double lipid bilayer surrounding the nucleus; continuous with ER.

Nuclear pore

Protein channel in the nuclear envelope permitting passage of RNA, proteins, and solutes.

Nucleolus

Dense nuclear region that produces rRNA for ribosome assembly.

Chromatin

DNA plus associated proteins in threadlike form within the nucleus.

Chromosome

Condensed form of chromatin visible during mitosis; humans have 46 per somatic cell.

DNA replication

Semiconservative copying of DNA before cell division, producing two identical molecules.

Helicase

Enzyme that unwinds and separates the two DNA strands during replication initiation.

DNA polymerase

Enzyme that adds complementary nucleotides to a growing DNA strand during elongation.

Semiconservative replication

Replication mode in which each new DNA molecule contains one original and one new strand.

Gene

Functional DNA segment that encodes information to build a specific protein.

Transcription

Nuclear process that converts DNA code of a gene into messenger RNA.

Translation

Cytoplasmic process in which ribosomes convert mRNA sequence into an amino-acid chain (protein).

Messenger RNA (mRNA)

Single-stranded RNA carrying a copy of genetic code from nucleus to ribosome.

RNA polymerase

Enzyme that synthesizes mRNA by adding RNA nucleotides complementary to DNA template.

Cell cycle

Ordered sequence from a cell’s creation to its division into two daughter cells.

Interphase

Non-dividing portion of cell cycle comprising G1, S, and G2 phases.

G1 phase

Interphase stage of cell growth and normal metabolic activities.

S phase

Interphase stage in which DNA is replicated.

G2 phase

Interphase stage involving continued growth and preparation for mitosis.

Mitotic phase

Period encompassing mitosis (nuclear division) and cytokinesis (cytoplasmic division).

Mitosis

Equitable division of duplicated chromosomes into two nuclei; consists of prophase, metaphase, anaphase, telophase.

Cytokinesis

Division of cytoplasm resulting in two separate daughter cells.

Prophase

First mitotic stage: chromosomes condense, nuclear envelope breaks down, spindle forms.

Metaphase

Second mitotic stage: sister chromatids align at the cell’s equatorial metaphase plate.

Anaphase

Third mitotic stage: sister chromatids separate and move to opposite poles.

Telophase

Fourth mitotic stage: chromosomes decondense, nuclear envelopes reform around each set.

Cleavage furrow

Contractile microfilament band that pinches animal cells in two during cytokinesis.

Mitotic spindle

Microtubule structure that attaches to kinetochores and segregates chromosomes during mitosis.

Hematopoiesis

Formation of blood cellular components from multipotent stem cells.

Totipotent stem cell

Most versatile stem cell able to give rise to all embryo and extra-embryonic tissues.

Pluripotent stem cell

Stem cell that can differentiate into cells of all three germ layers but not extra-embryonic tissues.

Multipotent stem cell

Stem cell restricted to producing multiple cell types within a particular lineage (e.g., blood).