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Cell biology vocabulary words

This list collects the vocabulary that comes up again and again in a cell biology unit, from the parts of a cell to how cells divide and get energy. It is meant for students preparing for a life science class, reviewing before a quiz, or reading about cell structure and function for the first time.

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Cell biology vocabulary words

Word	Meaning	In a sentence
membranenoun	A thin, flexible layer of tissue that covers, lines, or separates parts of an organism.	The cell membrane controls which substances can enter or leave the cell.
nucleusnoun	The central part of an atom or cell that contains most of its mass or genetic material.	The cell's nucleus holds the DNA that directs its growth and function.
cytoplasmnoun	The jelly-like material inside a cell, excluding the nucleus, where most cellular activities occur.	Organelles such as mitochondria float within the cytoplasm of the cell.
mitochondrianoun	Small structures within cells that convert nutrients into usable energy for the cell.	Muscle cells contain many mitochondria because they need a constant supply of energy.
ribosomenoun	A cell structure made of RNA and protein that builds proteins by translating genetic instructions.	Ribosomes read messenger RNA and assemble amino acids into a growing protein chain.
chromosomenoun	A thread-like structure of tightly coiled DNA that carries genes and passes hereditary information to offspring.	Humans typically have forty-six chromosomes arranged in twenty-three pairs within each cell.
chromatinnoun	The complex of DNA and proteins that forms chromosomes and packages genetic material within a cell nucleus.	Under the microscope, the chromatin appeared as a tangled mass of thread-like fibers inside the nucleus.
mitosisnoun	The process by which a cell divides its nucleus to produce two genetically identical daughter cells.	Mitosis allows a single fertilized egg to develop into billions of cells with the same DNA.
meiosisnoun	A type of cell division that produces reproductive cells containing half the usual number of chromosomes.	The biology class studied how meiosis creates genetic variation among offspring.
cytokinesisnoun	The process in which the cytoplasm of a single cell divides to form two separate daughter cells.	Cytokinesis follows the division of the nucleus, splitting the cell into two.
organellenoun	A specialized structure within a cell that performs a specific function, such as a mitochondrion.	The mitochondrion is an organelle that converts nutrients into usable energy for the cell.
osmosisnoun	The gradual movement of a solvent through a membrane from a less concentrated to a more concentrated solution.	Water enters plant roots by osmosis, moving from the soil into cells with higher salt concentration.
diffusionnoun	The gradual spreading or mixing of particles, ideas, or substances from an area of high concentration to a lower one.	The diffusion of gas molecules across the room happened faster in the warm air.
prokaryotenoun	A single-celled organism, such as a bacterium, that lacks a nucleus and other membrane-bound organelles.	Bacteria are prokaryotes because their genetic material floats freely inside the cell.
eukaryotenoun	An organism whose cells contain a nucleus enclosed within a membrane.	Plants, animals, and fungi are all eukaryotes, unlike bacteria.
vacuolenoun	A fluid-filled space enclosed by a membrane within a cell, used for storage, digestion, or maintaining structure.	The biology diagram showed a large central vacuole inside the plant cell.
chloroplastnoun	A structure inside plant and algae cells that contains chlorophyll and carries out photosynthesis.	Chloroplasts capture sunlight and convert it into chemical energy for the plant.
lysosomenoun	A small structure within a cell that contains enzymes to break down waste and unwanted material.	Lysosomes digest worn-out cell parts and recycle their components for reuse.
cytoskeletonnoun	A network of protein filaments within a cell that gives it shape, structure, and the ability to move.	The cytoskeleton helps the cell maintain its shape under mechanical stress.
centromerenoun	The region of a chromosome where the two sister chromatids join and spindle fibers attach during cell division.	The centromere ensures that chromosomes separate evenly when a cell divides.
nucleolusnoun	A small, dense structure inside the nucleus of a cell where ribosomes are produced.	Under the microscope, the nucleolus appeared as a dark spot within the nucleus.
spindlenoun	A slender rod used to twist and wind fiber into thread, or any similar rotating shaft.	She used a wooden spindle to spin the wool into yarn.
gametenoun	A mature reproductive cell, such as a sperm or egg, that unites with another to form a new organism.	In humans, the male gamete is the sperm and the female gamete is the egg.
zygotenoun	The single cell formed when a sperm cell and an egg cell fuse during fertilization.	Within hours of fertilization, the zygote begins dividing rapidly to form an embryo.
haploidadjective	Having a single complete set of chromosomes, as in a reproductive cell.	Human sperm and egg cells are haploid, each carrying half the usual genetic material.
diploidadjective	Having two complete sets of chromosomes, one inherited from each parent.	Most human body cells are diploid, containing forty-six chromosomes in total.
enzymenoun	A protein produced by living cells that speeds up a specific chemical reaction in the body.	The enzyme lactase helps the body break down sugar found in milk.
respirationnoun	The process by which living organisms take in oxygen and release carbon dioxide to produce energy.	Respiration in humans occurs mainly through the lungs, where oxygen enters the bloodstream.
photosynthesisnoun	The process in which plants, algae, and some bacteria use light energy to make sugars.	The leaves use light for photosynthesis.
cell wallnoun	A rigid outer layer surrounding the membrane of plant, fungal, and bacterial cells, providing structure and protection.	The cell wall gives plant cells their rigid, box-like shape.

The cell membrane

The cell membrane is the thin barrier that surrounds a cell and controls what moves in and out. Related words describe how that movement happens, such as diffusion, when particles spread from crowded areas to less crowded ones, and osmosis, when water moves across the membrane. Knowing these terms helps explain why cells stay balanced instead of bursting or shrinking.

Mitosis and meiosis

Mitosis and meiosis are both forms of cell division, but they serve different purposes. Mitosis produces two identical cells used for growth and repair, while meiosis produces reproductive cells with half the usual number of chromosomes. Words like chromatin, spindle, and cytokinesis describe specific steps and structures involved in these processes.

Frequently asked questions

What is the difference between mitosis and meiosis?

Mitosis produces two identical cells for growth and repair, while meiosis produces reproductive cells, like sperm and eggs, with half the usual number of chromosomes.