Cells: Structure and Function Vocabulary

Vocabulary flashcards defining cellular organelles, structures, and surface modifications based on lecture notes.

Cytoplasm

The jelly-like fluid interior of a cell that surrounds the organelles.

Organelles

Specialized structures within a cell that perform specific cellular functions.

Nucleus

A large organelle near the center of the cell that contains genetic material (DNA) and nucleoli, and serves as the site of RNA synthesis and ribosomal subunit assembly.

Nuclear Envelope

A double-membrane structure consisting of outer and inner membranes separated by a narrow space that bounds the nucleus.

Nuclear Pores

Openings in the nuclear envelope through which materials can pass into or out of the nucleus.

Chromatin

Loosely coiled DNA and protein structures present during most of a cell's life.

Chromosomes

Tightly coiled structures of DNA that form when a cell prepares to divide; human cells contain $23$ pairs.

Nucleolus

A dense structure within the nucleus (typically $1$ to $3$ per nucleus) where ribosomal subunits are assembled.

Ribosomes

Organelles containing RNA and protein, produced in the nucleolus, that serve as the site of protein synthesis.

Free Ribosomes

Ribosomes floating unattached in the cytoplasm that produce proteins used within the cell.

Rough Endoplasmic Reticulum

A membranous network studded with ribosomes that synthesizes and transports proteins.

Smooth Endoplasmic Reticulum

A membranous network without ribosomes that synthesizes lipids, participates in cellular detoxification, and stores calcium ions.

Golgi Apparatus

A series of closely packed curved membrane sacs that collects, modifies, and packages proteins and lipids into secretory vesicles.

Secretory Vesicle

A membrane-bound vesicle formed by the Golgi apparatus that contains materials produced in the cell to be released outside by exocytosis.

Lysosome

A membrane-bound vesicle formed by the Golgi apparatus containing digestive enzymes that break down waste and foreign material.

Peroxisome

A small membrane-bound vesicle containing enzymes that break down fatty acids, amino acids, and toxic hydrogen peroxide ($H_2O_2$).

Mitochondrion

A double-membraned organelle that produces ATP through aerobic metabolism and serves as the cell's main energy source.

Cristae

Folds of the inner mitochondrial membrane that project into the interior matrix to increase surface area.

Cytoskeleton

A cellular framework of protein fibers that provides structural support, holds organelles in place, and enables cell movement.

Microtubules

Hollow cytoskeleton tubules with the largest diameter ($25\,nm$) that support cytoplasm, assist in cell division, and form cilia and flagella.

Microfilaments

Small protein fibrils with the smallest diameter ($8\,nm$) involved in cell movement, muscle contraction, and maintaining cell shape.

Intermediate Filaments

Cytoskeleton protein fibrils with a medium diameter ($10\,nm$) that provide mechanical support and help maintain cell shape.

Keratin

A specific intermediate filament protein associated with structural support in skin cells.

Centrosome

A specialized region of cytoplasm near the nucleus where microtubule formation occurs, containing a pair of centrioles.

Centrioles

Cylindrical organelles composed of microtubule triplets that facilitate chromosome movement during cell division.

Microvilli

Non-motile cell membrane extensions composed of microfilaments that increase surface area for absorption.

Cilia

Microtubule-based cell surface projections (hundreds per cell) that move substances like mucus across cell surfaces.

Flagella

Long, single microtubule projections (one per cell) that propel entire cells, such as sperm cells.