Dental and Biomedical Sciences 1: Cell Biology Part B

Comprehensive vocabulary flashcards covering the organelles, protein transport, cell division cycle, apoptosis, necrosis, and cytoskeleton from the Cell Biology Part B lecture.

Nuclear Pores

Protein channels spanning both the inner and outer nuclear membranes that allow selective, bidirectional transport of RNA, proteins, and molecules between the nucleus and cytosol.

$5'$ Capping

The post-transcriptional addition of a methylated guanine nucleotide to the $5'$ end of pre-mRNA, which increases mRNA stability and facilitates nuclear export for translation.

Polyadenylation

The post-transcriptional addition of a few hundred adenine nucleotides to the $3'$ end of an RNA transcript to increase mRNA stability and enable export from the nucleus.

RNA Splicing

The processing mechanism in eukaryotic cells where non-coding intron sequences are removed from newly transcribed RNA transcripts.

Nuclear Import Receptor

A cytosolic transport factor that binds to larger molecules to facilitate their passage across nuclear pore complexes into the nucleus.

Mitochondria

Double-membrane-enclosed organelles responsible for cellular respiration, consuming oxygen and generating $CO_2$ to produce ATP.

Cristae

Inward folds of the inner mitochondrial membrane that project into the matrix, expanding the membrane surface area and the intermembrane space.

Mitochondrial Matrix

The internal compartment enclosed by the inner mitochondrial membrane where molecules derived from glycolysis, such as pyruvate and NADH, are metabolized.

Oxidative Phosphorylation

The process on the inner mitochondrial membrane where high-energy electrons pass through the electron transport chain to pump $H^+$ into the intermembrane space, creating a gradient that drives ATP synthesis from ADP and inorganic phosphate.

Protein Translocators

Membrane-embedded protein complexes that assist unfolded polypeptide strands in crossing organelle membranes, such as those of the mitochondria and endoplasmic reticulum.

Chaperone Proteins

Lumenal proteins that bind to incoming unfolded polypeptide strands as they emerge from translocators, pulling them into the organelle and assisting with correct refolding.

Endoplasmic Reticulum (ER)

A single-membrane endomembrane system continuous with the outer nuclear membrane that functions as the site of synthesis for membrane lipids, cell components, and secreted molecules.

Rough Endoplasmic Reticulum

Regions of the ER studded with ribosomes on the cytosolic surface that translate mRNAs and deliver synthesized proteins directly into the ER lumen.

Smooth Endoplasmic Reticulum

Ribosome-lacking ER regions involved in lipid and hormone synthesis, detoxification of organic molecules, and sequestration of calcium for cell signaling and mineralized tissue function.

Cisternae

Flattened, membrane-enclosed sacs organized in stacks of $3\text{--}20$ to form the functional structure of the Golgi apparatus.

Cis Golgi Network

The entry face of the Golgi apparatus located adjacent to the endoplasmic reticulum where newly synthesized proteins enter.

Trans Golgi Network

The exit face of the Golgi apparatus oriented toward the plasma membrane from which sorted, modified proteins bud off in transport vesicles.

Exocytosis

The outward transport pathway wherein transport vesicles originating from the trans Golgi network fuse with the plasma membrane to secrete molecules into the extracellular space.

Endocytosis

The inward vesicular pathway whereby material is ingested at the plasma membrane and delivered to endosomes for sorting and breakdown.

Lysosome

A degradative organelle that fuses with endosomes containing ingested material to break down substrates using lumenal degradative enzymes.

Signal Sequence

A peptide sequence typically ranging from a few up to $60$ amino acids at the amino or carboxy terminus of a protein that determines its targeted destination in the cell.

Cell Division Cycle

An ordered sequence of events consisting of cell growth and chromosome duplication, chromosome segregation, and cell division into daughter cells.

Interphase

The extended growth phase of the cell cycle comprising $G_1$, $S$, and $G_2$ phases, during which environmental conditions are monitored and DNA is replicated.

$S$ Phase

The DNA synthesis phase of the cell cycle during which chromosomes and genetic material are completely duplicated.

$M$ Phase

The cell cycle division phase composed of mitosis (nuclear division) and cytokinesis (cytoplasmic division).

Cyclin-Dependent Kinases (CdKs)

Conserved protein kinases that control transitions at cell cycle checkpoints by phosphorylating target proteins when bound to their regulatory cyclin partner.

Cyclins

Regulatory proteins that bind to CdKs to expose their active sites, switching on kinase activity at specific stages of the cell cycle.

Necrosis

Accidental, unregulated cell death caused by severe injury, characterized by cellular and organelle swelling, membrane rupture, leakage of intracellular contents, and pro-inflammatory responses.

Apoptosis

Programmed, non-inflammatory cell death in which chromatin condenses, the cell blebs and packages contents into apoptotic bodies, and fragments are cleared by phagocytes.

Caspases

A family of intracellular proteases synthesized as preformed, inactive zymogens that regulate and execute the apoptotic cell death pathway.

Initiator Caspases

First-responder pro-apoptotic proteases that activate via dimerization and cleavage in response to apoptotic stimuli to cleave and activate executioner caspases.

Executioner Caspases

Downstream proteases cleaved and activated by initiator caspases that cleave multiple cellular substrates, driving the execution of apoptosis.

Cytoskeleton

A dynamic intracellular network of protein filaments capable of rapid assembly and disassembly to maintain cell morphology, facilitate movement, and organize organelles.

Actin Filaments

Fine helical polymers of actin protein concentrated heavily in the cytoplasm directly beneath the plasma membrane to support mechanical stability and cell shape.

Intermediate Filaments

Rope-like protein fibers with high tensile strength and flexibility that form an extensive network throughout the cell to resist mechanical stress.

Microtubules

Rigid, hollow cylinders composed of tubulin dimers that grow out from the centrosome to organize intracellular architecture and construct the mitotic spindle.