Chapter 3: Cell Biology, Organelles, Protein Synthesis, and Cell Cycle

Comprehensive vocabulary flashcards covering cell organelles, endomembrane transport, nuclear structures, protein synthesis stages, DNA replication enzymes, and the cell cycle stages from Chapter 3 self-study notes.

Cytosol (Intracellular Fluid / ICF)

The watery, gel-like fluid inside the cell that forms part of the cytoplasm.

Cytoplasm

Everything inside the plasma membrane except the nucleus, consisting of cytosol, organelles, and the cytoskeleton.

Membrane-Enclosed Organelles

Cellular structures surrounded by a membrane, including mitochondria, nucleus, peroxisomes, endoplasmic reticulum, Golgi apparatus, and lysosomes.

Organelles Without a Surrounding Membrane

Cellular structures lacking a membrane enclosure, including ribosomes, centrosome/centrioles, and the cytoskeleton.

Mitochondria

Membrane-enclosed organelles that convert energy stored in nutrients into ATP to power cellular work.

Intermembrane Space (Mitochondrial)

The gap between the outer and inner mitochondrial membranes that stores hydrogen ions ($\text{H}^+$) for ATP synthesis.

Cristae

The highly folded inner membrane layer of a mitochondrion that increases surface area available for ATP synthesis.

Mitochondrial Matrix

The innermost space of a mitochondrion containing enzymes for the Krebs cycle, mitochondrial DNA, and ribosomes to catabolize nutrients and release energy.

Peroxisomes

Membrane-enclosed organelles that break down fatty acids and detoxify drugs and alcohol by using oxidase enzymes to convert toxins into hydrogen peroxide, which is then broken down into water and oxygen.

Ribosomes

Non-membrane-enclosed protein-building structures composed of a large subunit and a small subunit, found free in cytosol or bound to membranes.

Endomembrane System

A group of membranes and organelles (nuclear envelope, ER, transport vesicles, Golgi apparatus, lysosomes, plasma membrane) working together to synthesize, modify, package, and transport proteins and lipids.

Rough Endoplasmic Reticulum (RER)

Membrane network studded with ribosomes that builds, folds, modifies, and quality-checks proteins before packaging them into transport vesicles.

Smooth Endoplasmic Reticulum (SER)

Membrane network lacking ribosomes that synthesizes lipids, steroid hormones, and lipoproteins, stores $\text{Ca}^{2+}$, and detoxifies drugs and harmful substances.

Golgi Apparatus

Membrane-enclosed organelle that receives products from the ER to modify, sort, label, and package them into transport vesicles for delivery.

Lysosomes

Membrane-enclosed organelles containing acid hydrolases that digest and recycle materials, break down worn-out organelles via autophagy, and destroy ingested foreign material.

Autophagy

The process by which lysosomes digest and break down worn-out cellular organelles.

Microtubules

The thickest and strongest cytoskeleton elements, formed as hollow tubes from tubulin proteins, which maintain cell architecture, move organelles/vesicles, and form cilia, flagella, centrioles, and the mitotic spindle.

Intermediate Filaments

Ropelike protein fibers of the cytoskeleton that provide mechanical strength, support the nucleus, and connect adjacent cells so tissues resist stress.

Actin Filaments (Microfilaments)

The thinnest cytoskeleton elements, composed of intertwined strands of actin proteins, which support the cell surface, bear tension, change cell shape, and assist in cell crawling and muscle contraction.

Microvilli

Short, finger-like folds of the plasma membrane that increase surface area for efficient absorption of nutrients.

Cilia

Numerous short, hair-like extensions arranged in a $9 + 2$ microtubule setup that beat synchronously to move materials across the cell surface.

Flagellum

A single long tail extension with a $9 + 2$ microtubule setup that propels an entire cell, found in humans exclusively on sperm cells.

Centrosome

The microtubule-organizing center near the nucleus containing a pair of centrioles.

Centrioles

Paired microtubule structures inside the centrosome that duplicate and organize the mitotic spindle during cell division.

Nuclear Envelope

A double phospholipid bilayer that encloses the nucleus and regulates the movement of materials in and out through nuclear pores.

Nucleoplasm

The gel-like fluid inside the nucleus containing DNA, proteins, nucleotides, and enzymes.

Nucleolus

A dense structure inside the nucleus responsible for producing rRNA and assembling ribosomal subunits.

Chromatin

A less-condensed form of DNA wrapped around histones, present when the cell is not actively dividing.

Histones

Proteins around which DNA coils to form organized chromatin structures.

Nucleosome

A structural unit of chromatin consisting of DNA wrapped around histone proteins, resembling a bead on a string.

Chromosome

Tightly condensed chromatin structure containing genetic information, visible during cell division.

Sister Chromatids

Two identical copies of a chromosome produced during DNA replication, joined together at the centromere.

Centromere

The specialized region of a chromosome where two sister chromatids are joined together.

Gene

A specific segment of DNA containing instructions for synthesizing a functional product, typically a protein.

Transcription

The first stage of protein synthesis, occurring in the nucleus, where a gene's DNA sequence is copied into messenger RNA (mRNA).

RNA Polymerase

The primary enzyme in transcription that unwinds DNA and links complementary RNA nucleotides to synthesize mRNA.

Translation

The second stage of protein synthesis, occurring at a ribosome, where mRNA codons are read to assemble amino acids into a polypeptide chain.

Posttranslational Modification

The final stage of protein synthesis, occurring in the cytosol, RER, or Golgi apparatus, where a newly built polypeptide chain folds, gets trimmed, or receives chemical modifications to become fully functional.

Cell Cycle

The ordered series of events in a cell's life leading from its origin through growth and DNA replication to division into two daughter cells.

Interphase

The major phase of the cell cycle during which the cell grows, performs metabolic activities, and copies its DNA; composed of $G_1$, S, and $G_2$ subphases.

$G_1$ Phase

The first gap phase of interphase where the cell performs normal functions, grows, and produces organelles and proteins.

S Phase

The synthesis phase of interphase where DNA replication takes place to create duplicate copies of all chromosomes.

$G_2$ Phase

The second gap phase of interphase where the cell completes final preparations, makes proteins required for division, and duplicates its centrioles.

$G_0$ Phase

A non-dividing state entered by specific cells that exit the active cell cycle.

Helicase

The enzyme during DNA replication that unzips the DNA double helix by breaking hydrogen bonds between complementary base pairs.

Primase

The enzyme that synthesizes a short RNA primer to provide a starting point for DNA polymerase during DNA replication.

DNA Polymerase

The enzyme that pairs free complementary DNA nucleotides to the template strand to construct new DNA strands during replication.

DNA Ligase

The enzyme that seals gaps in the sugar-phosphate backbone and links DNA fragments together into continuous strands.

Prophase

The first phase of mitosis during which chromatin condenses into visible chromosomes, the nuclear envelope and nucleolus disassemble, centrosomes move apart, and the mitotic spindle forms.

Metaphase

The second phase of mitosis during which replicated chromosomes align along the equator or metaphase plate of the cell.

Anaphase

The third phase of mitosis during which sister chromatids separate at the centromere and are pulled toward opposite poles of the cell.

Telophase

The final phase of mitosis during which chromosomes reach opposite poles, decondense, nuclear envelopes and nucleoli reform, and the spindle disassembles.

Cytokinesis

The process following nuclear division where a cleavage furrow pinches the plasma membrane to divide the cytoplasm and organelles into two daughter cells.