AP Bio Chapter 4 Vocab

Actin

A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other kinds of cells.

Basal body

A eukaryotic cell structure consisting of a '9 + 0' arrangement of microtubule triplets that organizes the microtubule assembly of a cilium or flagellum and is structurally similar to a centriole.

Cell fractionation

The disruption of a cell and separation of its parts by centrifugation at successively higher speeds.

Cell wall

A protective layer external to the plasma membrane in plants, prokaryotes, fungi, and some protists, composed of structural polysaccharides such as cellulose, chitin, or peptidoglycan.

Central vacuole

A large membranous sac in a mature plant cell with diverse roles in growth, storage, and sequestration of toxic substances.

Centriole

A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a '9 + 0' pattern.

Centrosome

A structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and contains a pair of centrioles.

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.

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes, existing in a dispersed form of long, thin fibers when the cell is not dividing.

Chromosome

A cellular structure consisting of one DNA molecule and associated protein molecules that carries genetic material.

Cilium

A short cellular appendage containing microtubules, specialized either for locomotion and fluid movement ('9 + 2' arrangement) or for sensory and signaling roles ('9 + 0' arrangement).

Collagen

A glycoprotein in the extracellular matrix of animal cells that forms strong fibers; found extensively in connective tissue and bone, making it the most abundant protein in the animal kingdom.

Contractile vacuole

A membranous sac that helps move excess water out of certain freshwater protists.

Crista

An infolding of the inner membrane of a mitochondrion that houses electron transport chains and ATP synthase.

Cytoplasm

The contents of the cell enclosed by the plasma membrane, exclusive of the nucleus in eukaryotic cells.

Cytoskeleton

A network of microtubules, microfilaments, and intermediate filaments that extends throughout the cytoplasm and serves mechanical, transport, and signaling functions.

Cytosol

The semifluid portion of the cytoplasm in which subcellular components are suspended.

Dynein

A large motor protein in cilia and flagella extending between microtubule doublets that uses ATP hydrolysis to drive bending movements.

Electron microscope (EM)

A microscope that uses magnets to focus an electron beam on or through a specimen, achieving practical resolution up to 100-fold greater than a light microscope.

Endomembrane system

The collection of membranes inside and surrounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.

Endoplasmic reticulum (ER)

An extensive membranous network in eukaryotic cells continuous with the outer nuclear membrane, composed of ribosome-studded (rough) and ribosome-free (smooth) regions.

Endosymbiont theory

The theory stating that mitochondria and plastids originated as prokaryotic cells engulfed by host cells, subsequently evolving into a single organism.

Eukaryotic cell

A type of cell characterized by having a membrane-enclosed nucleus and membrane-enclosed organelles.

Extracellular matrix (ECM)

The meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides, and proteoglycans synthesized and secreted by the cells.

Fibronectin

An extracellular glycoprotein secreted by animal cells that helps them attach to the extracellular matrix.

Flagellum

A long cellular appendage specialized for locomotion, featuring a core of nine outer doublet microtubules and two inner single microtubules ('9 + 2' arrangement) in eukaryotic cells.

Food vacuole

A membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell.

Glycoprotein

A protein with one or more covalently attached carbohydrates.

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 noncellulose carbohydrates.

Granum

A stack of membrane-bounded thylakoids in the chloroplast that functions in the light reactions of photosynthesis.

Integrin

A transmembrane receptor protein in animal cells with two subunits that interconnects the extracellular matrix and the cytoskeleton.

Intermediate filament

A component of the cytoskeleton that includes fibers intermediate in size between microtubules and microfilaments.

Light microscope (LM)

An optical instrument with lenses that refract visible light to magnify images of specimens.

Lysosome

A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.

Microfilament

A cable composed of actin proteins in the cytoplasm of eukaryotic cells, acting alone or with myosin to cause cell contraction.

Microtubule

A hollow rod composed of tubulin proteins that forms part of the cytoskeleton in eukaryotic cells and structural components of cilia and flagella.

Middle lamella

A thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young plant cells.

Mitochondrial matrix

The compartment enclosed by the inner membrane of a mitochondrion, containing enzymes, ribosomes, and DNA for the citric acid cycle.

Mitochondrion

An organelle in eukaryotic cells that serves as the site of cellular respiration, using oxygen to break down organic molecules and synthesize ATP.

Motor protein

A protein that interacts with cytoskeletal elements and other cellular components to produce movement of the cell or its internal parts.

Myosin

A type of motor protein that forms filaments interacting with actin filaments to cause muscle and cellular contraction.

Nuclear envelope

The double membrane perforated with pores that surrounds the nucleus in a eukaryotic cell, continuous with the endoplasmic reticulum.

Nuclear lamina

A netlike array of protein filaments lining the inner surface of the nuclear envelope that maintains nuclear shape.

Nucleoid

A non-membrane-enclosed region in a prokaryotic cell where its DNA chromosome is concentrated.

Nucleolus

A specialized structure within the nucleus where ribosomal RNA (rRNA) is synthesized and ribosomal subunits are assembled.

Nucleus

The central organelle of a eukaryotic cell containing the genetic material in the form of chromosomes composed of chromatin.

Organelle

Any of several membrane-enclosed structures with specialized functions suspended in the cytosol of eukaryotic cells.

Peroxisome

An organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen ($O_2$), producing and then degrading hydrogen peroxide ($H_2O_2$).

Phagocytosis

A type of endocytosis in which large particulate substances or small organisms are engulfed and taken up by a cell.

Plasma membrane

The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition.