Chapter 4 vocab

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 the cells of plants, prokaryotes, fungi, and some protists.

Central vacuole

In a mature plant cell, a large membranous sac 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 plus 0” pattern.

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.

Chromosome

A cellular structure consisting of one DNA molecule and associated protein molecules.

Cilium (cilia)

A short appendage containing microtubules in eukaryotic cells.

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. The inner membrane houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP

cytoplasm

The contents of the cell enclosed by the plasma membrane; in eukaryotes, the portion exclusive of the nucleus.

cytoskeleton

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

cytosol

The semifluid portion of the cytoplasm.

Electron microscope

A microscope that uses magnets to focus an electron beam on or through a specimen, resulting in a practical resolution 100-fold greater than that of a light microscope using standard techniques.

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; includes the plasma membrane, the nuclear envelope, the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, and vacuoles.

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.

eukaryotic cell

A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles.

Flagellum (fagelle)

A long cellular appendage specialized for locomotion.

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 some products, notably noncellulose carbohydrates.

granum

A stack of membrane-bounded thylakoids in the chloroplast. Grana function in the light reactions of photosynthesis.

Intermediate filament

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

light microscope

An optical instrument with lenses that refract (bend) 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 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.

Micro tubule

A hollow rod composed of tubulin proteins that makes up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella.

Mitochondrial matrix

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

mitochondrion

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

Nuclear envelope

In a eukaryotic cell, the double membrane that surrounds the nucleus, perforated with pores that regulate traffic with the cytoplasm. The outer membrane is continuous with the endoplasmic reticulum.

Nucleoid

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

nucleolus

A specialized structure in the nucleus consisting of chromosomal regions containing ribosomal RNA (rRNA) genes along with ribosomal proteins imported from the cytoplasm; site of rRNA synthesis and ribosomal subunit assembly. *See also* ribosome.

organelle

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

Nucleus

An atom’s central core, containing protons and neutrons. (2) The organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes, made up of chromatin. (3) A cluster of neurons.

peroxisome

An organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen (O2), producing and then degrading hydrogen peroxide (H2O2).

Phagocytosis

A type of endocytosis in which large particulate substances or small organisms are 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.

Prokaryotic cell

A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles.

Ribosome

A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large subunit and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus. *See also* nucleolus.

rough ER

That portion of the endoplasmic reticulum with ribosomes attached.

Scanning electron microscope

A microscope that uses an electron beam to scan the surface of a sample, coated with metal atoms, to study details of its topography.

smooth ER

That portion of the endoplasmic reticulum that is free of ribosomes.

stroma

The dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA; involved in the synthesis of organic molecules from carbon dioxide and water.

Thylakoid

A flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular “machinery” used to convert light energy to chemical energy.

Transmission Electron Microscope

A microscope that passes an electron beam through very thin sections stained with metal atoms and is primarily used to study the internal structure of cells.

Transport vesicle

A small membranous sac in a eukaryotic cell’s cytoplasm carrying molecules produced by the cell.

Vesicle

A membranous sac in the cytoplasm of a eukaryotic cell.