Unit 1 Lab and Lecture Review: Histology, Cytology, and Cytoskeleton

Vocabulary practice flashcards covering cell histology methods, cytology, plasma membrane components, cytoskeletal structure, motor proteins, cell adhesion molecules, and cell junctions.

Hematoxylin

A positive, basic histological stain that binds to negatively charged cellular molecules such as nuclei and histones.

Eosin

A negative, acidic histological stain that binds to positively charged cellular molecules such as the cytoplasm and cell membrane.

Direct Immunohistochemistry

A technique where a primary animal antibody specific to a target antigen is directly labeled with a tag and applied to tissue.

Indirect Immunohistochemistry

A technique where an untagged primary antibody binds to an antigen, and a tagged secondary antibody (e.g., goat anti-mouse Ab) binds to the primary antibody.

Artifacts

Mistakes or unintended alterations introduced during preparation steps (such as staining, cutting, or fixing) that appear on the final slide.

Prokaryotic Cells

Cells characterized by circular chromosomes and the absence of a nucleus, organelles, or cytoskeleton.

Eukaryotic Cells

Cells containing a nucleus, membrane-bound organelles, a cytoskeleton, and linear chromosomes.

Glycocalyx

A carbohydrate-rich cell coat on the outer plasma membrane surface involved in cell recognition, cell-cell interactions, and mechanical protection.

Microfilaments

Cytoskeletal filaments measuring $7\,\text{nm}$ in diameter, composed of helical F-actin subunits assembled from G-actin monomers.

Intermediate Filaments

Stable cytoskeletal structures measuring $10\,\text{nm}$ in diameter, formed from unit-length filaments (ULFs) made of $8$ tetramers.

Microtubules

Hollow cytoskeletal tubes measuring $25\,\text{nm}$ in diameter, consisting of $13$ protofilaments formed by $\alpha\text{-tubulin}$ and $\beta\text{-tubulin}$ heterodimers.

Treadmilling

A process in actin microfilaments where subunits assemble at the barbed (+$) end and disassemble at the pointed (-$)$ end.

Dynamic Instability

The dynamic behavior of microtubules characterized by rapid switching between growth (polymerization) and catastrophe (shrinkage) at the ($$+$) end.

Profilin

An actin-binding protein that facilitates monomer addition (polymerization) to F-actin via $\text{ATP} \rightarrow \text{ADP}$ exchange.

Cofilin (ADF)

An actin-binding protein that depolymerizes microfilaments by removing individual monomers.

Gelsolin

An actin-binding protein that caps F-actin to prevent monomer addition or removal, or severs microfilaments in the presence of $\text{Ca}^{2+}$.

ARP2/3

A protein complex located at branching sites that promotes microfilament branching, such as in stereocilia.

Formin

A protein with FH1 and FH2 domains located at the cap that regulates unbranched cell projections such as microvilli.

Centrosome

A microtubule organizing center (MTOC) consisting of a pair of centrioles surrounded by pericentriolar material (PCM).

Axoneme

The structural core of motile cilia and flagella, consisting of $9$ outer microtubule doublets surrounding a central pair ($9+2$ structure).

Kinesin

A motor protein that walks along microtubules toward the ($$+$) end to perform long-range anterograde intracellular transport.

Cytoplasmic Dynein

A motor protein that walks along microtubules toward the ($-$)$$ end to perform long-range retrograde intracellular transport.

Myosin I

An unconventional motor protein with one head and a tail that binds to the cell membrane and moves vesicles short distances along actin filaments.

Myosin II

A conventional motor protein whose dimer tails weave together into long chains to mediate contraction in muscle sarcomeres.

Cadherins

$\text{Ca}^{2+}$-dependent adhesion molecules that form cis-homophilic dimers on the same membrane and trans-homophilic dimers with neighboring cells, linked to actin via catenin complexes.

Selectins

$\text{Ca}^{2+}$-dependent cell adhesion molecules that bind to carbohydrates through a carbohydrate-recognition domain (CRD).

Integrins

Heterodimeric adhesion proteins made of $\alpha$ and $\beta$ subunits whose extracellular domains bind to RGD motifs on laminin and fibronectin.

Tight Junctions

Cellular junctions that prevent paracellular leaking and maintain cell polarity by separating the apical and basolateral membrane domains.

Zonula Adherens

Belt desmosomes that form a circumferential belt around the apical domain, linking microfilaments to cytoplasmic desmosome cadherins via catenin complexes.

Macula Adherens

Spot desmosomes that anchor cells together using tonofilaments connected to cytoplasmic plaques such as plakoglobin.

Hemidesmosomes

Junctions that anchor epithelial cells to the basal lamina by linking intermediate filaments (tonofilaments) via inner cytoplasmic plaques and outer membrane plaques.

Connexon

A channel composed of six assembled connexin proteins that forms a gap junction for direct electrical and chemical signaling between cells.