Cellular Level of Organization

Vocabulary practice flashcards covering cell structure, organelles, nuclear components, and division based on lecture slides.

Cell

The structural and functional unit of a living organism, defined as a mass of protoplasm enclosed within a membrane and containing a nucleus.

Protoplasm

The basic substance present in all living cells.

Cytoplasm

The portion of the cell that lies between the plasma membrane and the nuclear membrane, consisting of approximately $90\%$ fluid containing free amino acids, proteins, glucose, and other molecules.

Mitosis

A process of somatic cell duplication involving $1$ cell division that produces $2$ identical diploid daughter cells.

Meiosis

A reduction division process producing reproductive cells (gametes) through $2$ cell divisions that yield $4$ genetically distinct haploid daughter cells.

Prokaryotic cells

Cells lacking a nucleus, typically represented by bacteria with sizes ranging from $1\text{ to }2\,\mu\text{m}$.

Eukaryotic cells

Cells containing a distinct nucleus, ranging in size from approximately $5\text{ to }100\,\mu\text{m}$.

Organelles

Specialized living structures present within the cytoplasm of a cell.

Inclusions

Non-living substances stored or suspended in the cytoplasm, including glycogen, fat, secretion granules, and pigments.

Plasma membrane

A lipid/protein/carbohydrate complex providing a selective barrier to the cell and housing transport and signaling systems.

Glycocalyx

A thin outer layer on the extracellular face of the plasma membrane formed by carbohydrate groups of glycoproteins and glycolipids.

Karyotheca

The nuclear membrane bounding the nucleus, consisting of two unit membranes separated by a space and perforated by nuclear pores.

Nucleoplasm

The nuclear sap or ground substance found inside the nucleus.

Nucleolus

A large, spherical granule within the nucleus whose primary function is the biogenesis of ribosomes.

Chromatin

Thread-like, coiled, and elongated nucleoprotein structures present in the nucleoplasm (derived from Greek for colour).

Chromosomes

Ribbon-like structures that form from condensed chromatin fibers during cell division (mitosis and meiosis).

Heterochromatin

The darkly stained, condensed chromatin region located around the nucleolus and at the nuclear periphery; it is metabolically and genetically inert, containing a small amount of DNA and a large amount of RNA.

Euchromatin

The lightly stained, diffused region of chromatin that contains a comparatively large amount of DNA.

Golgi complex

A disc-shaped organelle with central flattened cisternae, a peripheral tubular network, and vesicles, involved in the formation and packaging of materials for cellular export.

Granular (Rough) endoplasmic reticulum

Endoplasmic reticulum studded with surface ribosomes, found abundantly in cells active in protein synthesis and acting as an intracellular transport system.

Agranular (Smooth) endoplasmic reticulum

Endoplasmic reticulum lacking ribosomes, typically found in cells not actively synthesizing proteins, and responsible for the synthesis of lipids, glycogen, and steroids.

Ribosomes

Small, dense, rounded particles composed of ribonucleoprotein that assemble amino acids into polypeptide chains during protein synthesis.

Lysosomes

Tiny, membrane-bounded vesicular structures performing intracellular digestion, colloquially known as the "suicide bags" of the cell.

Centrioles

Two cylindrical, rod-shaped microtubular structures near the nucleus lacking limiting membranes and nucleic acids, which form the mitotic apparatus during cell division.

Basal body

A modified centriole positioned beneath the plasma membrane in flagellated or ciliated cells that bears and organizes a flagellum or cilium.

Peroxisomes

Self-replicating, lysosome-like organelles containing oxidative enzymes and a crystalline core, responsible for protecting the cell from toxic substances such as hydrogen peroxide.

Glyoxisomes

Specialized plant and yeast microbodies with a dense rod crystalloid core that contain enzymes for fatty acid metabolism and gluconeogenesis.

Mitochondria

Double-membraned organelles known as the "power houses" of the cell, which contain circular DNA, $70\text{S}$ ribosomes, and replicate via binary fission.

Cristae

Plate-like or tubular inward folds of the inner mitochondrial membrane that significantly increase its surface area.

Microfilaments

Cytoskeletal protein filaments that stabilize cell shape and facilitate cell motility.

Microtubules

Tubular cytoskeletal components that act as tracks along which materials move within the cell.

Vacuoles

Membrane-bound sac-like organelles in plant cells that store water and nutrients.

Chloroplasts

Double-membraned plant plastids containing DNA and stacked thylakoid membranes, responsible for trapping light energy and performing photosynthesis.