AP Biology Vocabulary & Word Roots: Ch. 6
1. actin- A globular protein that links into chains, two of which twist helically about each other, forming
microfilaments (actin filaments) in muscle and other kinds of cells.
2. basal body-A eukaryotic cell structure consisting of a 9 + 0 arrangement of microtubule triplets. The
basal body may organize the microtubule assembly of a cilium or flagellum and is structurally very
similar to a centriole.
3. capsule-(1) A sticky layer that surrounds the cell wall of some prokaryotes, protecting the cell surface
and sometimes helping to glue the cell to surfaces.
4. cell fractionation-The disruption of a cell and separation of its parts by centrifugation.
5. central vacuole-A membranous sac in a mature plant cell with diverse roles in reproduction, growth,
and development.
6. centriole-A structure in the centrosome of an animal cell composed of a cylinder of microtubule
triplets arranged in a 9 + 0 pattern. A centrosome has a pair of centrioles.
7. centrosome-Structure present in the cytoplasm of animal cells, important during cell division;
functions as a microtubule-organizing center. A centrosome has two centrioles.
8. chloroplast-An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it
to drive the synthesis of organic compounds from carbon dioxide and water.
9. chromatin-The complex of DNA and proteins that makes up a eukaryotic chromosome. When the
cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not
visible with a light microscope.
10. chromosome-A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells.
Each chromosome consists of one very long DNA molecule and associated proteins. (A bacterial
chromosome usually consists of a single circular DNA molecule and associated proteins. It is found in
the nucleoid region, which is not membrane bounded.) See also chromatin.
11. cilium- (plural, cilia) A short cellular appendage containing microtubules. A motile cilium is
specialized for locomotion and is formed from a core of nine outer doublet microtubules and two inner
single microtubules (the “9 + 2” arrangement) ensheathed in an extension of the plasma membrane. A
primary cilium is usually nonmotile and plays a sensory and signaling role; it lacks the two inner
microtubules (the “9 + 0” arrangement).
12. collagen-A glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found
extensively in connective tissue and bone; the most abundant protein in the animal kingdom.
13. contractile vacuole-A membranous sac that helps move excess water out of certain freshwater
protists.
14. crista-(plural, cristae) An infolding of the inner membrane of a mitochondrion that houses electron
transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase).
15. cytoplasm-The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane.
16. cytoplasmic streaming-A circular flow of cytoplasm, involving myosin and actin filaments, that
speeds the distribution of materials within cells.
17. cytoskeleton-A network of microtubules, microfilaments, and intermediate filaments that branch
throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions.
18. cytosol-The semifluid portion of the cytoplasm.
19. desmosome-A type of intercellular junction in animal cells that functions as a rivet.
20. dynein-In cilia and flagella, a large contractile protein extending from one microtubule doublet to
the adjacent doublet. ATP hydrolysis drives changes in dynein shape that lead to bending of cilia and
flagella.
21. electron microscope (EM)-A microscope that uses magnets to focus an electron beam on or through
a specimen, resulting in resolving power a thousandfold greater than that of a light microscope. A
transmission electron microscope (TEM) is used to study the internal structure of thin sections of cells.
A scanning electron microscope (SEM) is used to study the fine details of cell surfaces.
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22. endomembrane system-The collection of membranes inside and around a eukaryotic cell, related
either through direct physical contact or by the transfer of membranous vesicles; includes the smooth
and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles.
23. endoplasmic reticulum (ER)-An extensive membranous network in eukaryotic cells, continuous
with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free
(smooth) regions.
24. eukaryotic cell-A type of cell with a membrane-enclosed nucleus and membrane-enclosed
organelles. Organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotes.
25. extracellular matrix (ECM)-The substance in which animal cells are embedded, consisting of
protein and polysaccharides synthesized and secreted by cells.
26. fibronectin-A glycoprotein that helps animal cells attach to the extracellular matrix.
27. flagellum- (plural, flagella) A long cellular appendage specialized for locomotion. Like motile cilia,
eukaryotic flagella have a core with nine outer doublet microtubules and two inner single microtubules
ensheathed in an extension of the plasma membrane. Prokaryotic flagella have a different structure.
28. food vacuole-A membranous sac formed by phagocytosis of microorganisms or particles to be used
as food by the cell.
29. gap junction-A type of intercellular junction in animals that allows the passage of materials between
cells.
30. glycoprotein-A protein with one or more carbohydrates covalently attached to it.
31. Golgi apparatus-An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that
modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably
noncellulose carbohydrates.
32. granum- (plural, grana) A stack of membrane-bounded thylakoids in the chloroplast. Grana function
in the light reactions of photosynthesis.
33. integrin-in animal cells, a transmembrane receptor protein that interconnects the extracellular matrix
and the cytoskeleton.
34. intermediate filament-A component of the cytoskeleton that includes filaments intermediate in size
between microtubules and microfilaments.
35. light microscope (LM)-An optical instrument with lenses that refract (bend) visible light to magnify
images of specimens.
36. lysosome-A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells
and some protists.
37. microfilament-A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell,
making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction; also
known as an actin filament.
38. microtubule-A hollow rod composed of tubulin proteins that make up part of the cytoskeleton in all
eukaryotic cells and is found in cilia and flagella.
39. middle lamella-In plants, a thin layer of adhesive extracellular material, primarily pectins, found
between the primary walls of adjacent young cells.
40. mitochondrial matrix-The compartment of the mitochondrion enclosed by the inner membrane and
containing enzymes and substrates for the citric acid cycle.
41. mitochondrion- (plural, mitochondria) An organelle in eukaryotic cells that serves as the site of
cellular respiration.
42. motor protein-A protein that interacts with cytoskeletal elements and other cell components,
producing movement of the whole cell or parts of the cell.
43. nuclear envelope-The double membrane in a eukaryotic cell that encloses the nucleus, separating it
from the cytoplasm.
44. nuclear lamina-A netlike array of protein filaments lining the inner surface of the nuclear envelope;
it helps maintain the shape of the nucleus.
45. nucleoid-A dense region of DNA in a prokaryotic cell.
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46. nucleolus- (plural, nucleoli) A specialized structure in the nucleus, consisting of chromatin regions
containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasmic site of
rRNA synthesis and ribosomal subunit assembly. See also ribosome.
47. nucleus- (2) The chromosome-containing organelle of a eukaryotic cell.
48. organelle-Any of several membrane-enclosed structures with specialized functions, suspended in the
cytosol of eukaryotic cells.
49. peroxisome-An organelle containing enzymes that transfer hydrogen (H2) from various substrates to
oxygen (O2), producing and then degrading hydrogen peroxide (H2O2).
50. phagocytosis-A type of endocytosis in which large particulate substances are taken up by a cell. It is
carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages,
neutrophils, and dendritic cells).
51. plasma membrane-The membrane at the boundary of every cell that acts as a selective barrier,
regulating the cell’s chemical composition.
52. plasmodesma- (plural, plasmodesmata) An open channel in the cell wall of a plant through which
strands of cytosol connect from an adjacent cell.
53. plastid-One of a family of closely related organelles that includes chloroplasts, chromoplasts, and
amyloplasts (leucoplasts). Plastids are found in cells of photosynthetic organisms.
54. primary cell wall-In plants, a relatively thin and flexible layer first secreted by a young cell.
55. prokaryotic cell-A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed
organelles. Organisms with prokaryotic cells (bacteria and archaea) are called prokaryotes.
56. proteoglycan-A glycoprotein consisting of a small core protein with many carbohydrate chains
attached, found in the extracellular matrix of animal cells. A proteoglycan may consist of up to 95%
carbohydrate.
57. pseudopodium- (plural, pseudopodia) A cellular extension of amoeboid cells used in moving and
feeding.
58. ribosomal RNA (rRNA)-The most abundant type of RNA, which together with proteins makes up
ribosomes.
59. ribosome-A complex of rRNA and protein molecules that functions as a site of protein synthesis in
the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in
the nucleolus. See also nucleolus.
60. rough ER-That portion of the endoplasmic reticulum studded with ribosomes.
61. scanning electron microscope (SEM)-A microscope that uses an electron beam to scan the surface
of a sample to study details of its topography.
62. secondary cell wall-In plants, a strong and durable matrix often deposited in several laminated
layers for cell protection and support.
63. smooth ER-That portion of the endoplasmic reticulum that is free of ribosomes.
64. stroma-Within the chloroplast, the dense fluid of the chloroplast surrounding the thylakoid
membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
65. thylakoid- A flattened membranous sac inside a chloroplast. Thylakoids exist in an interconnected
system in the chloroplast and contain the molecular “machinery” used to convert light energy to
chemical energy.
66. tight junction-A type of intercellular junction in animal cells that prevents the leakage of material
between cells.
67. transmission electron microscope (TEM)-A microscope that passes an electron beam through very
thin sections and is primarily used to study the internal ultrastructure of cells.
68. transport vesicle-A tiny membranous sac in a cell’s cytoplasm carrying molecules produced by the
cell.
69. vacuole-A membrane-bounded vesicle whose function varies in different kinds of cells.
70. vesicle-A sac made of membrane in the cytoplasm.
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Word Roots
centro- = the center; -soma = a body (centrosome: structure present in the cytoplasm of all animal cells,
important during cell division)
chloro- = green (chloroplast: the site of photosynthesis in plants and algae)
cili- = hair (cilium: a short hair-like cellular appendage with a microtubule core)
cyto- = cell (cytosol: a semifluid medium in a cell in which are located organelles)
-ell = small (organelle: a small membrane-enclosed structure with a specialized function found in the
cytoplasm of eukaryotic cells)
endo- = inner (endomembrane system: the system of membranes within a cell that includes the nuclear
envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and the plasma membrane)
eu- = true (eukaryotic cell: a cell that has a true nucleus)
extra- = outside (extracellular matrix: the substance in which animal tissue cells are embedded)
flagell- = whip (flagellum: a long whip-like cellular appendage that moves cells)
glyco- = sweet (glycoprotein: a protein covalently bonded to a carbohydrate)
lamin- = sheet/layer (nuclear lamina: a netlike array of protein filaments that maintains the shape of the
nucleus)
lyso- = loosen (lysosome: a membrane-enclosed sac of hydrolytic enzymes that a cell uses to digest
macromolecules)
micro- = small; -tubul = a little pipe (microtubule: a hollow rod of tubulin protein in the cytoplasm of
almost all eukaryotic cells)
nucle- = nucleus; -oid = like (nucleoid: the region where the genetic material is concentrated in
prokaryotic cells)
phago- = to eat; -kytos = vessel (phagocytosis: a form of cell eating in which a cell engulfs a smaller
organism or food particle)
plasm- = molded; -desma = a band or bond (plasmodesmata: an open channel in a plant cell wall)
pro- = before; karyo- = nucleus (prokaryotic cell: a cell that has no nucleus)
pseudo- = false; -pod = foot (pseudopodium: a cellular extension of amoeboid cells used in moving and
feeding)
thylaco- = sac or pouch (thylakoid: a series of flattened sacs within chloroplasts)
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tono- = stretched; -plast = molded (tonoplast: the membrane that encloses a large central vacuole in a
mature plant cell)
trans- = across; -port= a harbor (transport vesicle: a membranous compartment used to enclose and
transport materials from one part of a cell to another)
ultra- = beyond (ultracentrifuge: a machine that spins test tubes at the fastest speeds to separate liquids
and particles of different densities)
vacu- = empty (vacuole: sac that buds from the ER, Golgi, or plasma membrane)
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