Membrane Proteins, Cytoskeleton, and Cell Junctions (Video Notes)

Vocabulary flashcards covering membrane protein types (integral, peripheral, lipid-anchored), their functions (channels, carriers, receptors, markers), cytoskeleton components (actin, intermediate filaments, microtubules) and their roles, and cell junctions (tight, adherens, desmosomes, hemidesmosomes, gap junctions) as described in the video notes.

Integral (transmembrane) proteins

Proteins that span the entire phospholipid bilayer, closely associated with the membrane; often function as channels or carriers.

Peripheral proteins

Proteins with weaker membrane association that attach to integral proteins or to phospholipid heads; can be removed without disrupting the membrane.

Lipid-anchored proteins

Proteins inserted into the bilayer and covalently bonded to lipid tails, anchored in the membrane interior.

Channel proteins

Membrane proteins that provide a passageway for specific ions or small molecules to cross the membrane.

Carrier proteins

Membrane transport proteins that bind to a substance and change shape to shuttle it across the membrane.

Receptors

Membrane proteins that bind signals (such as hormones) and induce a conformational change to transmit a message, sometimes without entering the cell.

Identification markers

Membrane proteins with attached carbohydrate groups (glycoproteins) used to recognize self versus non-self.

Cytoskeleton

Internal framework of the cell made of actin filaments, intermediate filaments, and microtubules; maintains shape and organizes components.

Actin filaments (microfilaments)

Thinnest cytoskeletal fibers involved in cell movement, shape changes, and vesicle transport.

Intermediate filaments

Cytoskeletal fibers of intermediate diameter; important in cell junctions and mechanical strength.

Microtubules

Largest cytoskeletal fibers, hollow tubes; maintain cell shape and distribute organelles.

Functions of the cytoskeleton

Maintains cell shape, moves components, transports materials, helps tissue assembly, and enables movement.

Tight junctions

Junctions that restrict movement between cells, forming a barrier to prevent leakage of contents between cells.

Adherens junctions

Anchoring junctions that connect actin networks of neighboring cells to hold cells together.

Desmosomes

Anchoring junctions that connect intermediate filaments between cells to resist tearing under tension.

Hemidesmosomes

Anchoring junctions that attach epithelial cells to the extracellular matrix by linking intermediate filaments to the basal membrane.

Gap junctions

Channels between neighboring cells formed by proteins, allowing direct passage of ions and small molecules; can be open or closed.

Extracellular matrix

Matrix outside the cell composed of proteins and polysaccharides that interacts with membrane proteins and the cytoskeleton.

Signal transduction via membrane receptor

Binding of a signal to a membrane protein triggers a conformational change that transmits the message inside the cell.

Conformational change

Shape change in a protein upon ligand binding that enables signal transmission.