Module 3 Lecture 3 Cell Components and Junctions

Vocabulary terms covering cell structure, the cytoskeleton, the endomembrane system, and intercellular junctions based on Chapter 3 Lecture 3.

Cytoplasm

Comprises the contents of the cell between the plasma membrane and the nuclear envelope; it is 70% - 80% water with a semi-solid consistency.

Cytosol

The fluid portion of the cytoplasm.

Cytoskeleton

A network of protein fibres throughout the cytoplasm that maintains cell shape, secures organelles, and enables cell movement and division.

Microfilaments (Actin filaments)

The thinnest cytoskeleton component, consisting of long rods of actin about $7\,nanometres$ in diameter, involved in cell division and muscle contraction.

Intermediate filaments

Cytoskeletal fibres measuring $10\,nanometres$ in size that maintain cell shape and anchor organelles; keratin is a common example.

Microtubules

Hollow tubes composed of tubulin, $25\,nanometres$ in diameter, that guide organelle movement and serve as structural components of flagella.

Endomembrane system

A coordinated system consisting of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and cell membrane.

Nucleus

The organelle that contains most of the Eukaryotic cell’s DNA and directs the synthesis of ribosomes.

Nucleolus

An area within the nucleus that aggregates ribosomal RNA with proteins to assemble ribosomal subunits.

Endoplasmic reticulum (ER)

A series of interconnected membrane tubules and flattened vesicles that modify proteins and synthesize lipids.

Rough ER

A region of the ER with ribosomes attached, primarily involved in protein synthesis.

Smooth ER

A region of the ER continuous with the Rough ER but without ribosomes, responsible for lipid synthesis and detoxification.

Vesicles

Membrane-bound sacs used to transport materials within a cell.

Golgi apparatus

A stack of thin, flat, and slightly curved sacs involved in processing and sorting newly synthesized proteins.

Tight junction

A seal between cells that prevents fluid from leaking between them, such as those found in the bladder.

Anchoring (adhering) junctions

Junctions that fasten cells together, allowing them to be arranged into a sheet, found in cells like the outer skin layer.

Gap junction

Channels that form tunnels between animal cells allowing water and ions to pass, typically found in neurons and muscle cells.

Plasmodesmata

Structural equivalents of gap junctions that occur in plant cell walls to allow substance movement between cells.