Cell Organelles and Structures

Vocabulary practice flashcards covering cell classifications, organelles, endomembrane trafficking, structural components, and viral anatomy.

Prokaryotic Cell

A unicellular organism lacking a nucleus and membrane-bound organelles, characterized by DNA located in an unbound region called the nucleoid and typically measuring $1\text{--}5\,\mu\text{m}$ (or $0.1\text{--}10\,\mu\text{m}$) in diameter.

Eukaryotic Cell

A cell containing membrane-bound organelles and a nucleus bounded by a membranous nuclear envelope, typically measuring $10\text{--}100\,\mu\text{m}$ in diameter.

Cytosol

The semi-fluid, gel-like substance present in all cells in which subcellular components and organelles are suspended.

Plasma Membrane

A selectively permeable phospholipid bilayer containing proteins and carbohydrates that envelops the cell surface and regulates the transport of materials entering and exiting the cell.

Surface Area-to-Volume Ratio

The physical constraint dictating that as a cell expands, its volume increases faster than its surface area ($4\pi r^2$ vs. $\frac{4}{3}\pi r^3$), requiring cells to remain small to efficiently exchange materials and maintain homeostasis.

Cytoskeleton

A scaffolding network of protein filaments that organizes internal structures and plays an essential role in cell shape, movement, and division.

Cilia

Hair-like projections extending from eukaryotic cells that beat in coordinated waves to move unicellular organisms or clear microbes and debris from the respiratory tract lining.

Flagella

Tail-like projection(s) on bacteria, animals, and protists that propel cells forward through a whip-like motion.

Pseudopod

A temporary cytoplasm-filled projection ("fake foot") extended by cytoskeleton microfilaments used for locomotion and food ingestion in certain unicellular organisms.

Centriole

A tubular-shaped organelle constructed of microtubules found in animal cells that aids in organizing cell division.

Cytoplasm

The cellular region located between the plasma membrane and the nucleus, which includes the cytosol, the cytoskeleton, and all suspended organelles.

Nucleus

The command center of a eukaryotic cell that controls cellular activities and stores DNA containing genetic instructions for synthesizing proteins.

Nuclear Envelope

A double-membrane boundary with inner and outer layers that encloses the nucleus, separating its genetic contents from the cytoplasm.

Nuclear Pores

Protein-lined channel complexes penetrating the nuclear envelope that regulate the passage of macromolecules, RNA, and particles into and out of the nucleus.

Chromatin

The diffuse complex of DNA and associated proteins housed within the eukaryotic nucleus.

Nucleolus

A prominent structure located within the eukaryotic nucleus responsible for ribosome assembly.

Ribosomes

Cellular organelles composed of ribosomal RNA and protein that carry out protein synthesis; they can function free in the cytosol or bound to the rough endoplasmic reticulum.

Smooth Endoplasmic Reticulum

A network of internal membranes lacking ribosomes that synthesizes lipids, ships them to the Golgi apparatus, and metabolizes toxic substances.

Rough Endoplasmic Reticulum

A network of internal membranes studded with ribosomes on its outer surface that synthesizes proteins and packages them into transport vesicles directed to the Golgi apparatus.

Golgi Apparatus

An organelle composed of flattened membranous sacs that receives lipids and proteins from the ER, modifies them through successive chambers, and packages them into vesicles for cellular distribution or secretion.

Transport Vesicles

Membranous spheres that bud from the smooth or rough endoplasmic reticulum to shuttle synthesized molecules to the Golgi apparatus or other destinations.

Secretory Vesicles

Membrane-bound spheres holding cellular products, such as hormones or neurotransmitters, that fuse with the plasma membrane to secrete their contents outside the cell.

Lysosomes

Digestive membrane sacs found in animal cells containing enzymes that degrade cellular waste, worn-out organelles, food particles, and foreign invaders.

Peroxisomes

Single-membrane-bound microbodies measuring $0.5\text{--}1.5\,\mu\text{m}$ that bud from the endoplasmic reticulum and specialize in oxidative metabolism and detoxification.

Central Vacuole

A large membrane-bound organelle found in mature plant cells that holds water and organic compounds, exerting turgor pressure to keep the cell rigid and the plant upright.

Contractile Vacuole

A specialized organelle found in many freshwater protists that accumulates and pumps excess water out of the cell to prevent lysis.

Mitochondria

Double-membrane organelles present in all eukaryotic cells that harvest energy from organic compounds to produce $\text{ATP}$ during cellular respiration.

Chloroplast

A photosynthetic organelle found in plant cells and some protists that utilizes light energy to produce glucose during photosynthesis.

Cell Wall

A fairly rigid extracellular layer located outside the plasma membrane that offers protection and support, present in plant, fungal, and algal cells.

Extracellular Matrix (ECM)

An intricate external network of glycoproteins and carbohydrate-containing molecules surrounding animal cells that provides support, adhesion, movement, and regulation.

Bacteriophage

A virus that infects bacteria, consisting of an icosahedral capsid head containing DNA, a neck, a sheath/tail, a base plate, and tail fibers.