The Cell: Structure, Permeability, and Organelles

A complete set of vocabulary flashcards covering the components, functions, and transport mechanisms of the cell and its organelles as described in the lecture notes.

Cell Theory

The principle that all living organisms are composed of one or more cells, all cells arise from pre-existing cells, and cells are the smallest structural and functional units of life.

Sex cells

Also known as gametes.

Somatic cells

All cells in the body except for sex cells (gametes).

Cell membrane

Also known as the plasmalemma or plasma membrane; a semipermeable membrane that regulates the passage of molecules into and out of the cell.

Nucleus

The control center of the cell that stores genetic information; can be anucleate (zero nuclei) or multinucleate (multiple nuclei).

Cytoplasm

Consists of the cytosol (a gelatinous mix of water and solutes) and organelles ("little organs").

Phospholipid bilayer

Two layers of phospholipids where hydrophilic heads face the extracellular and intracellular fluid, and hydrophobic tails orientate inward away from fluid.

Plasmalemma thickness

Measured at approximately $2\,nm$ in the phospholipid bilayer.

Fluid mosaic model

A model describing the cell membrane as a flexible layer made of lipid molecules is interspersed with large protein molecules and a glycocalyx.

Glycocalyx

A viscous, carbohydrate-rich barrier that provides protection, "stickiness", and acts as a "self vs non self" marker.

Peripheral proteins

Proteins located on the inside or outside of the membrane.

Integral proteins

Proteins embedded within the membrane.

Cholesterol

A molecule that stabilizes the cell membrane.

Tight Junctions

Fused membranes located on the apical surface of skin.

Desmosomes

Protein anchors that resist stress, found in cardiac muscle and skin.

Gap junctions

Communicating connections found in cardiac muscle and smooth muscle.

Diffusion

A passive process where solutes move from a region of high concentration to a region of low concentration until evenly distributed.

Facilitated Diffusion

A passive process where solutes are transported by a protein channel or carrier protein without requiring energy.

Osmosis

The diffusion of water across a membrane from a region of higher concentration to a region of lower concentration.

Active Transport

A process where proteins use ATP to transport solutes against a concentration gradient, such as the Sodium-Potassium pump.

Endocytosis

The movement of material from the extracellular space into the interior of the cell.

Phagocytosis

A type of endocytosis referred to as "cellular eating."

Pinocytosis

A type of endocytosis referred to as "cellular drinking."

Exocytosis

A process where vesicles fuse with the cell membrane to expel contents from the cell interior to the extracellular space.

Chromatin

The "loose" form of DNA found in a non-dividing cell.

Chromosomes

Rod-like structures formed from chromatin during cell division preparation.

Nuclear envelope

A double membrane containing nuclear pores that separates the nucleus from the cytoplasm.

Nucleolus

A dark-staining body within the nucleus responsible for synthesizing ribosomes.

Mitochondria

The "powerhouses" of the cell that provide ATP for energy and contain their own DNA.

Cristae

The infoldings of the inner mitochondrial membrane.

Matrix

The inner fluid of the mitochondria.

Rough ER (RER)

A network of membranes studded with ribosomes that manufactures all secreted proteins.

Smooth ER (SER)

A network of membranes that synthesizes lipids, including phospholipids, cholesterol, and other steroids.

Golgi apparatus

Also known as the Golgi Complex or "Post Office" of the cell; it packages products into lysosomes, membrane renewal vesicles, or secretory vesicles.

Lysosomes

Membranous sacs containing digestive enzymes used to digest organelles, destroy bacteria, or perform autolysis.

Autolysis

Programmed cell death or self-destruction.

Peroxisomes

Membranous sacs of oxidase enzymes that detoxify harmful substances like alcohol and break down free radicals.

Ribosomes

The "factories" of the cell made of protein and RNA; the site of protein synthesis which can be free or fixed to the RER.

Cytoskeleton

The "city planners" of the cell that provide an internal framework and support organelles; includes microfilaments, intermediate filaments, and microtubules.

Microfilaments

Cytoskeletal components concentrated under the plasma membrane that function in cell mobility and shape.

Intermediate filaments

Cytoskeletal proteins with high tensile strength that resist pulling forces on the cell.

Microtubules

Hollow tubes of protein that anchor and move organelles and form mitotic spindles during cell division.

Centrosome

A protein glob that generates microtubules and contains centrioles.

Centrioles

Bundles of short microtubules in a cylindrical structure that direct the formation of the mitotic spindle.

Microvilli

Immobile, finger-like extensions of the cell membrane that increase surface area for absorption.

Cilia

Mobile whip-like extensions made of microtubules that move substances along the cell surface, such as in the respiratory epithelium or fallopian tubes.

Flagella

Mobile whip-like extensions made of microtubules that propel the entire sperm cell.