Generalized Cell Structures and Somatic Cell Division

Vocabulary practice flashcards covering cell anatomy, organelle structure and function, and the phases of the somatic cell cycle based on the lecture material.

Plasma membrane

A flexible but sturdy fluid mosaic lipid bilayer (composed of phospholipids, cholesterol, and glycolipids) studded with proteins that surrounds the cytoplasm and mediates the entry and exit of substances.

Cytoplasm

The cellular contents between the plasma membrane and the nucleus, consisting of cytosol and organelles, serving as the site of all intracellular activities except those occurring in the nucleus.

Cytosol

The fluid portion of the cytoplasm (comprising $55\%$ of cell volume and $75\text{--}90\%$ water) containing dissolved solutes, suspended particles, lipid droplets, and glycogen granules where many metabolic reactions occur.

Fluid mosaic model

A structural model describing the plasma membrane as a continuously moving sea of lipids in which proteins float like icebergs, consisting of $50\%$ lipid and $50\%$ protein with roughly $50$ lipid molecules per protein molecule.

Nonmembranous organelles

Subcellular structures that lack surrounding lipid membranes and are in direct contact with the cytoplasm.

Membranous organelles

Subcellular structures surrounded by one or two lipid bilayer membranes that separate their contents from the cytosol.

Cytoskeleton

A network of three types of protein filaments throughout the cytosol (microfilaments, intermediate filaments, and microtubules) that maintains cell shape, organizes cellular contents, and aids cell movements.

Microfilaments

The thinnest cytoskeletal filaments composed of actin that function in cellular movement, division, and mechanical support for microvilli.

Intermediate filaments

Cytoskeletal filaments composed of several different proteins that stabilize organelle positions and provide structural resistance to mechanical stress.

Microtubules

Unbranched cylindrical cytoskeletal structures composed of tubulin that contribute to cell shape, structure of cilia, flagella, and centrosomes, and facilitate organelle transport and chromosome movement.

Centrosome

An organelle located near the nucleus consisting of a pair of centrioles and pericentriolar matrix, acting as the organizing center for growth of the mitotic spindle and microtubule formation.

Pericentriolar matrix

The region of the centrosome surrounding centrioles that contains tubulins used for microtubule formation and mitotic spindle growth.

Centrioles

A pair of cylindrical structures positioned at $90^\circ$ to each other inside the centrosome, composed of $9$ clusters of $3$ microtubules arranged in a $9+0$ array.

Cilia

Short, motile projections on the cell surface containing $20$ microtubules and a basal body that move fluids over the cell surface.

Flagella

Longer motile cell surface projections containing $20$ microtubules and a basal body that function to move an entire cell.

Ribosome

A nonmembranous organelle composed of two subunits containing ribosomal RNA and proteins that functions as the site of protein synthesis.

Free ribosomes

Ribosomes floating unattached in the cytosol that synthesize proteins used internally within the cell.

Membrane-bound ribosomes

Ribosomes attached to the endoplasmic reticulum or nuclear envelope that synthesize proteins destined for insertion in plasma membranes or for export via exocytosis.

Polyribosome

A structural complex composed of $10$ to $20$ ribosomes attached together in a linear chain.

Endoplasmic reticulum

An extensive membranous network of flattened sacs or tubules called cisterns that accounts for half of the total membranous surface area inside the cytoplasm.

Rough ER

Endoplasmic reticulum continuous with the nuclear envelope and covered with attached ribosomes that synthesizes, processes, and packages glycoproteins and phospholipids.

Smooth ER

Endoplasmic reticulum lacking ribosomes that synthesizes fatty acids and steroids, detoxifies harmful substances, removes phosphate from glucose-6-phosphate, and stores calcium ions in muscle cells.

Cisternae

Flattened membranous sacs found within organelles such as the endoplasmic reticulum and Golgi complex.

Golgi complex

An organelle consisting of $3\text{--}20$ flattened membranous sacs (cisternae) organized into entry (cis) face, medial cisternae, and exit (trans) face that modifies, sorts, and packages proteins.

Entry (cis) face

The convex surface of the Golgi complex that accepts transport vesicles containing newly synthesized proteins from the rough ER.

Exit (trans) face

The concave surface of the Golgi complex that sorts, packages, and releases modified molecules into vesicles for transport to their destinations.

Lysosome

A membrane-enclosed vesicle formed by the Golgi complex containing digestive enzymes that break down endocytosed substances, worn-out organelles, or entire cells.

Autophagy

The process by which lysosomal enzymes digest worn-out cellular organelles.

Autolysis

The destruction of an entire cell through digestion by its own lysosomal enzymes.

Peroxisome

A membrane-bound vesicle containing oxidases and catalase that breaks down fatty acids and amino acids while detoxifying hydrogen peroxide and free radicals.

Proteasome

A tiny barrel-shaped structure containing proteases that degrades unneeded, damaged, or faulty cellular proteins into small peptides.

Mitochondrion

A double-membraned organelle consisting of cristae and matrix that serves as the primary site for aerobic respiration reactions generating ATP.

Mitochondrial cristae

Folds of the internal mitochondrial membrane that provide an expanded surface area for cellular respiration chemical reactions.

Nucleus

A large organelle enclosed by a double-membrane nuclear envelope with water-filled pores that houses the cell's genetic units (genes and chromosomes).

Nucleolus

A non-membranous spherical body located inside the nucleus responsible for producing and assembling ribosomes.

Chromatin

A tangled mass of loosely packed DNA and histone proteins visible in the nucleus of non-dividing (interphase) cells.

Mitosis

Nuclear division in somatic cells leading to the distribution of two identical sets of chromosomes into two separate nuclei.

Cytokinesis

The division of a cell's cytoplasm where a contractile ring forms a cleavage furrow to split the parent cell into two separate, equal daughter cells.

$G_0$ phase

A state outside the active cell cycle in which non-dividing cells remain in $G_1$ for an extended duration or permanently.