Topic 12 – Eukaryotic Cell Structure

Vocabulary flashcards covering key cell-structure terms, organelles, processes, and theories from Topic 12 on eukaryotic cells.

Surface Area-to-Volume Ratio

Mathematical relationship explaining why cells remain small; volume increases faster than surface area, limiting nutrient exchange.

Eukaryotic Cell

Cell type possessing a nucleus and membrane-bound organelles; includes animal, plant, fungal, and protist cells.

Prokaryotic Cell

Smaller cell type lacking a nucleus and membrane-bound organelles; includes bacteria and archaea.

Plasma Membrane

Selectively permeable phospholipid bilayer that regulates entry and exit of substances in all cells.

Cell Wall

Rigid outer layer found in plants (cellulose), fungi (chitin), and some protists; provides strength and osmotic protection.

Endocytosis

General process of importing material into a eukaryotic cell by membrane invagination and vesicle formation.

Exocytosis

Process of exporting material from a cell when vesicles fuse with the plasma membrane.

Phagocytosis

Type of endocytosis in which solid particles are engulfed to form a food vacuole (phagosome).

Pinocytosis

Type of endocytosis in which extracellular fluid and dissolved solutes are ingested (‘cell drinking’).

Vacuole

Membrane-bound sac; large central in plants for storage and turgor, small and numerous in animals for transport or waste.

Vesicle

Small membrane-bound compartment that shuttles substances within or out of the cell.

Cytoplasm

Entire contents between plasma membrane and nucleus; includes organelles and cytosol.

Cytosol

Fluid portion of the cytoplasm bathing organelles.

Nucleus

Double-membrane organelle housing most cellular DNA; controls gene expression.

Nuclear Envelope

Double membrane surrounding the nucleus, containing pores for molecular transport.

Nucleolus

Dense nuclear region where ribosomal RNA (rRNA) is synthesized and ribosome subunits assemble.

Chromatin

DNA-protein complex forming long threads in the nucleus; condenses into chromosomes during division.

Ribosome

RNA-protein particle that translates mRNA into polypeptides; free in cytosol or bound to rough ER.

Endomembrane System

Interconnected membranes (ER, Golgi, lysosomes, vesicles, plasma membrane, nuclear envelope) that synthesize, modify, and transport biomolecules.

Rough Endoplasmic Reticulum (RER)

ER studded with ribosomes; synthesizes and transports proteins.

Smooth Endoplasmic Reticulum (SER)

ER lacking ribosomes; functions in lipid synthesis, detoxification, and calcium storage.

Golgi Apparatus

Stack of flattened sacs that modify, sort, and package proteins and lipids into vesicles for delivery.

Lysosome

Golgi-derived vesicle containing hydrolytic enzymes for intracellular digestion.

Microbody

General term for small enzyme-containing vesicles such as peroxisomes.

Peroxisome

Microbody that oxidizes fatty acids and toxins, forming H₂O₂ which catalase converts to water and oxygen.

Mitochondrion

Double-membrane organelle that performs aerobic respiration and ATP production; contains its own DNA and ribosomes.

Cristae

Folded inner membrane of mitochondria that increases surface area for ATP-producing reactions.

Chloroplast

Plant plastid with thylakoid membranes and chlorophyll; site of photosynthesis; contains DNA and ribosomes.

Granum

Stack of thylakoids within a chloroplast where light-dependent reactions occur.

Leucoplast

Colorless plastid that stores starch or oils in plant cells.

Plastid

Family of plant organelles including chloroplasts and leucoplasts with their own genetic material.

Endosymbiotic Theory

Idea that mitochondria and chloroplasts originated from free-living bacteria engulfed by ancestral eukaryotes; supported by their DNA and ribosomes.

Cytoskeleton

Network of protein filaments (actin, microtubules, intermediate filaments) providing structure, movement, and chromosome segregation.

Centrosome

Microtubule-organizing center containing a pair of centrioles; forms spindle fibers during cell division.

Flagellum (Eukaryotic)

Long whip-like appendage moving in 180° waves to propel cells such as sperm.

Cilium

Short, numerous hair-like projection beating rhythmically to move the cell or surrounding fluid (e.g., respiratory tract).