Cell Biology: Prokaryotic and Eukaryotic Structures

Vocabulary flashcards covering cellular structures, organelle functions, prokaryotic and eukaryotic distinctions, nuclear components, and metabolic storage disorders.

Prokaryotic Cell

A cell structure without a nuclear membrane covering its genetic material (DNA), directly submerged in cytoplasm, lacking membrane-bounded organelles, containing 70S ribosomes, and dividing by binary fission.

Eukaryotic Cell

A cell structure featuring a well-defined nucleus enclosed by a double nuclear membrane, 80S ribosomes, membrane-bounded organelles, and dividing via mitosis.

Sacculus

The entire prokaryotic cell wall, regarded as a single huge molecular complex composed of peptidoglycan or murein.

Peptidoglycan

A polymer composing the cell wall of prokaryotes, made of polysaccharide chains bound covalently to shorter chains of amino acids.

Nuclear Pores

Structures formed where the inner and outer nuclear membranes unite, controlling the exchange and traffic of materials between the nucleus and the cytoplasm.

Nucleolus

A darkly stained, non-membranous nuclear body composed of a peripheral granular area and central fibrillar area, responsible for synthesizing ribosomal RNA (rRNA) and assembling ribosomes.

Centromere

The region on a chromosome where sister chromatids are held together and spindle fibers attach during cell division.

Chromatid

An exact replica of a chromosome, paired with its twin and attached at the centromere at the start of cell division.

Diploid (2n)

The condition representing the normal number of chromosomes found in body cells, such as 46 in humans or 8 in Drosophila melanogaster.

Haploid (n)

The condition representing half the normal chromosome number, present in germ cells such as human sperm and egg cells containing 23 chromosomes.

Chloroplast

A double-membrane photosynthetic organelle in plant cells measuring $4\text{--}6\,\mu\text{m}$ in diameter, containing chlorophyll, stroma, and thylakoid grana.

Stroma

The fluid matrix surrounding thylakoids inside a chloroplast, containing circular DNA, ribosomes, and enzymes responsible for fixing $\text{CO}_2$ to manufacture sugars.

Thylakoid

A flattened vesicle inside a chloroplast that stacks into grana where light energy is trapped and ATP is formed.

Chromoplast

A pigment-containing plastid that imparts non-green colors to flower petals and ripened fruits to assist in pollination and seed dispersal.

Leucoplast

A colorless plastid of various shapes found in underground plant parts that functions in food storage.

Microtubules

Long, unbranched slender tubulin protein structures involved in maintaining cell shape and driving the assembly and disassembly of the spindle structure during mitosis.

Microfilaments

Slender contractile cylinders composed of actin protein attached to the inner face of the plasma membrane, involved in internal cell motion such as cyclosis and amoeboid movement.

Intermediate Filaments

Cytoskeletal elements with diameters between those of microtubules and microfilaments that maintain cell shape and integrate cellular compartments.

Centriole

An organelle present in animal cells and lower plants made of nine microtubule triplets, which duplicates prior to division to aid in spindle formation and cleavage furrowing.

Cristae

Infoldings of the inner mitochondrial membrane extending into the matrix that bear F1 particles and respiratory enzymes.

F1 Particles

Small knob-like structures located on the inner surface of cristae in the mitochondrial matrix involved in energy transformation.

Lysosomes

Single-membrane cytoplasmic sacs rich in acid phosphatase and hydrolytic enzymes, isolated by De Duve in 1949 for intracellular digestion.

Phagocytosis

The process by which foreign objects or food particles entering a cell are engulfed and broken down into simple digestible pieces.

Autophagosomes

Secondary lysosomes that engulf and digest old or damaged cellular organelles (such as old mitochondria) to recycle materials or generate energy.

Tay-Sachs Disease

A congenital lysosomal storage disease caused by the absence of an enzyme involved in lipid catabolism, resulting in lipid accumulation in brain cells, mental retardation, and death.

Glycogenosis Type II

A congenital lysosomal storage disease where liver and muscle tissues fill with glycogen in membrane-bound organelles due to the absence of an enzyme that degrades glycogen to glucose.

Peroxisome

A single-membrane cytoplasmic organelle ($0.5\,\mu\text{m}$ in diameter) containing catalase and oxidases involved in the formation and decomposition of hydrogen peroxide ($\text{H}_2\text{O}_2$).

Glyoxysomes

Plant organelles abundant in germinating lipid-rich seedlings containing enzymes for the glyoxylate cycle, which converts stored fatty acids to carbohydrates.