Cells

A comprehensive vocabulary flashcard set covering foundational cell biology concepts including organelle functions, membrane structures, transport mechanisms, and cellular components.

Cell

The basic, living, structural and functional unit of the body.

Plasma membrane

A lipid bilayer structural framework and barrier that separates the internal contents of a cell from the extracellular milieu.

Amphipathic

Refers to lipid molecules having both a hydrophilic polar head that faces outward toward watery fluid and hydrophobic nonpolar tails that face inward forming the hydrophobic core.

Integral membrane proteins

Proteins firmly embedded in the plasma membrane that extend half-way into or across the entire lipid bilayer.

Peripheral membrane proteins

Proteins located on the inner (cytoplasmic) or outer (extracellular) surface of the plasma membrane that are not embedded in the lipid bilayer.

Selective permeability

The property of the plasma membrane allowing unassisted passage to small nonpolar molecules like $O_2$ and $CO_2$, slight permeability to small uncharged polar molecules like water, and impermeability to ions and large polar molecules like glucose.

Ion channels

Integral membrane proteins that form tiny pores across the plasma membrane to allow specific ions, such as potassium ($K^+$), to enter or exit the cell.

Transporters

Integral membrane proteins (also known as carriers) that assist in the transport of specific molecules, such as glucose, across the plasma membrane.

Exocytosis

The transport of materials in a vesicle formed within a cell out to the extracellular environment.

Endocytosis

The uptake of materials from the extracellular environment into a vesicle formed from the plasma membrane.

Phagocytosis

A specific type of endocytosis involving the ingestion of solid particles like worn-out cells, bacteria, or viruses into a vesicle using pseudopods.

Phagocytes

Specialized cells, specifically macrophages and neutrophils, that carry out phagocytosis.

Cytoplasm

All the cellular contents between the plasma membrane and the nucleus, consisting of cytosol, cytoskeleton, and organelles.

Cytosol

The intracellular fluid composed of water, proteins, carbohydrates, lipids, and inorganic substances in solution or suspension where many metabolic reactions occur.

Inclusions

Insoluble aggregations of organic molecules suspended in cytosol that lack a surrounding membrane, such as lipid droplets and glycogen granules.

Cytoskeleton

A network of protein tubules and filaments providing structural framework and support to the cell, consisting of microfilaments, intermediate filaments, and microtubules.

Microfilaments

Thread-like protein filaments formed by actin ($5\text{ nm}$ to $7\text{ nm}$ in diameter) that function in movement, structural support, and forming the core of microvilli.

Intermediate filaments

Strong, rope-like protein filaments ($10\text{ nm}$ to $12\text{ nm}$ in diameter) that provide structural support, anchor organelles, and form tonofilaments of desmosomes.

Microtubules

Long, unbranched hollow tubules ($22\text{ nm}$ to $24\text{ nm}$ in diameter) formed by tubulin that grow from the centrosome to maintain shape, transport organelles, and form cilia and the mitotic spindle.

Cilia

Short, motile, hair-like projections of the plasma membrane containing a microtubule core that move substances like mucus across the cell surface.

Ribosome

The site of protein synthesis composed of a small subunit and a large subunit that join together in the cytoplasm.

Free ribosomes

Unattached ribosomes in the cytoplasm that synthesize proteins used within the cell.

Attached ribosomes

Ribosomes attached to the outer surface of the nuclear membrane or rough ER that synthesize integral membrane proteins, secretory proteins, or organelle proteins.

Rough Endoplasmic Reticulum (RER)

A network of flattened membranous cisternae continuous with the outer nuclear membrane and studded with ribosomes, involved in protein synthesis and post-translational modifications.

Smooth Endoplasmic Reticulum (SER)

A network of membranous tubules extending from the RER that lacks attached ribosomes and does not participate in protein synthesis.

Golgi complex

An organelle consisting of flattened membranous cisternae (cis face, medial cisternae, trans face) that receives, modifies, sorts, and packages newly synthesized proteins into vesicles.

Mitochondria

Spherical to filamentous double-membraned organelles known as the powerhouses of the cell that generate ATP via oxidative phosphorylation on inner membrane cristae.

Nucleus

A spherical or oval organelle that contains genetic material in the form of 23 pairs of chromosomes composed of DNA and histone proteins.

Nuclear envelope

A double membrane perforated by nuclear pores that separates nuclear contents from the cytoplasm and is continuous with the rough ER.

Nuclear pores

Water-filled openings in the nuclear envelope through which small molecules diffuse passively, and large particles like mRNAs and ribosomal subunits pass using energy and chaperone proteins.

Cell division

The process where a parental cell duplicates its 23 pairs of chromosomes ($2n = 46$) and organelles, then splits into two identical daughter cells.