Chapter 4: A Tour of the Cell

Question 1

cell theory

Answer 1

The theory that all living things are composed of cells and that all cells come from other cells.

Question 2

cell wall

Answer 2

A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists; protects the cell and helps maintain its shape.

Question 3

cellular metabolism

Answer 3

The chemical activities of cells.

Question 4

central vacuole

Answer 4

A membrane-enclosed sac occupying most of the interior of a mature plant cell, having diverse roles in reproduction, growth, and development.

Question 5

centriole

Answer 5

A structure in an animal cell composed of cylinders of microtubule triplets arranged in a 9 and 0 pattern. An animal usually has a centrosome with a pair of centrioles involved in cell division.

Question 6

chloroplast

Answer 6

An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic molecules (sugars) from carbon dioxide and water.

Question 7

chromatin

Answer 7

The complex of DNA and proteins that constitutes eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing.

Question 8

chromosome

Answer 8

A threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. Chromosomes consist of chromatin, a combination of DNA and protein.

Question 9

crista

Answer 9

(plural, cristae) An infolding of the inner membrane of a mitochondrion in which is embedded the electron transport chain and the enzyme catalyzing the synthesis of ATP.

Question 10

cytoplasm

Answer 10

Everything inside a cell between the plasma membrane and the nucleus; consists of a semifluid medium and organelles.

Question 11

cytoskeleton

Answer 11

A network of protein fibers in the cytoplasm of a eukaryotic cell; includes microfilaments, intermediate filaments, and microtubules.

Question 12

electron microscope (EM)

Answer 12

An instrument that focuses an electron beam through, or onto the surface of, a specimen. An electron microscope achieves a hundredfold greater resolution than a light microscope.

Question 13

endomembrane system

Answer 13

A network of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.

Question 14

endoplasmic reticulum (ER)

Answer 14

An extensive membranous network in a eukaryotic cell, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions. See also rough ER; smooth ER.

Question 15

endosymbiosis

Answer 15

A process by which the mitochondria and chloroplasts of eukaryotic cells probably evolved from symbiotic associations between small prokaryotic cells living inside larger cells.

Question 16

eukaryotic cell

Answer 16

A type of cell that has a membrane-enclosed nucleus and other membrane-enclosed organelles. All organisms except bacteria and archaea are composed of eukaryotic cells.

Question 17

extracellular matrix (ECM)

Answer 17

A substance in which the cells of an animal tissue are embedded; consists of protein and polysaccharides.

Question 18

flagellum

Answer 18

(plural, flagella) A long cellular appendage specialized for locomotion. The flagella of prokaryotes and eukaryotes differ in both structure and function. Like cilia, eukaryotic flagella have a 9 + 2 arrangement of microtubules covered by the cell’s plasma membrane.

Question 19

glycoprotein

Answer 19

A macromolecule consisting of one or more polypeptides linked to short chains of sugars.

Question 20

Golgi apparatus

Answer 20

An organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum.

Question 21

granum

Answer 21

(plural, grana) A stack of hollow disks formed of thylakoid membrane in a chloroplast. Grana are the sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis.

Question 22

intermediate filament

Answer 22

An intermediate-sized protein fiber that is one of the three main kinds of fibers making up the cytoskeleton of eukaryotic cells. Intermediate filaments are ropelike, made of fibrous proteins.

Question 23

light microscope (LM)

Answer 23

An optical instrument with lenses that refract (bend) visible light to magnify images and project them into a viewer’s eye or onto photographic film.

Question 24

lysosome

Answer 24

A digestive organelle in eukaryotic cells; contains hydrolytic enzymes that digest the cell’s food and wastes.

Question 25

microfilament

Answer 25

The thinnest of the three main kinds of protein fibers making up the cytoskeleton of a eukaryotic cell; a solid, helical rod composed of the globular protein actin.

Question 26

micrograph

Answer 26

A photograph taken through a microscope.

Question 27

microtubule

Answer 27

The thickest of the three main kinds of fibers making up the cytoskeleton of a eukaryotic cell; a straight, hollow tube made of globular proteins called tubulins. Microtubules form the basis of the structure and movement of cilia and flagella.

Question 28

mitochondrial matrix

Answer 28

The fluid contained within the inner membrane of a mitochondrion.

Question 29

mitochondrion

Answer 29

(plural, mitochondria) An organelle in eukaryotic cells where cellular respiration occurs. Enclosed by two concentric membranes, it is where most of the cell’s ATP is made.

Question 30

nuclear envelope

Answer 30

A double membrane, perforated with pores, which encloses the nucleus and separates it from the rest of the eukaryotic cell.

Question 31

nucleoid

Answer 31

A dense region of DNA in a prokaryotic cell.

Question 32

nucleolus

Answer 32

A structure within the nucleus of a eukaryotic cell where ribosomal RNA is made and assembled with proteins imported from the cytoplasm to make ribosomal subunits.

Question 33

nucleus

Answer 33

(plural, nuclei) (1) An atom’s central core, containing protons and neutrons. (2) The genetic control center of a eukaryotic cell.

Question 34

organelle

Answer 34

A membrane-enclosed structure with a specialized function within a cell.

Question 35

peroxisome

Answer 35

An organelle containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide.

Question 36

plasma membrane

Answer 36

The membrane that sets a cell off from its surroundings and acts as a selective barrier to the passage of ions and molecules into and out of the cell; consists of a phospholipid bilayer in which are embedded molecules of protein and cholesterol.

Question 37

plasmodesma

Answer 37

(plural, plasmodesmata) An open channel in a plant cell wall through which strands of cytoplasm connect from adjacent cells.

Question 38

prokaryotic cell

Answer 38

A type of cell lacking a membrane-enclosed nucleus and other membrane-enclosed organelles; found only in the domains Bacteria and Archaea.

Question 39

ribosome

Answer 39

A cell structure consisting of RNA and protein organized into two subunits and functioning as the site of protein synthesis in the cytoplasm. The ribosomal subunits are constructed in the nucleolus.

Question 40

rough ER

Answer 40

A network of interconnected membranous sacs in a eukaryotic cell’s cytoplasm. Rough ER membranes are studded with ribosomes that make membrane proteins and secretory proteins.

Question 41

scanning electron microscope (SEM)

Answer 41

A microscope that uses an electron beam to study the surface architecture of a cell or other specimen.

Question 42

stroma

Answer 42

The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water; Sugars are made in the stroma by the enzymes of the Calvin cycle.

Question 43

thylakoid

Answer 43

One of a number of disk-shaped membranous sacs inside a chloroplast. Thylakoid membranes contain chlorophyll and the enzymes of the light reactions of photosynthesis. A stack of thylakoids is called a granum.

Question 44

transmission electron microscope (TEM)

Answer 44

A microscope that uses an electron beam to study the internal structure of thinly sectioned specimens.

Question 45

transport vesicle

Answer 45

A tiny membranous sac in a cell’s cytoplasm carrying molecules produced by the cell. The vesicle buds from the endoplasmic reticulum or Golgi and eventually fuses with another membranous organelle or the plasma membrane, releasing its contents.

Question 46

vacuole

Answer 46

A membrane-enclosed sac that is part of the endomembrane system of a eukaryotic cell, having diverse functions.

Question 47

vesicle

Answer 47

A sac made of membrane in the cytoplasm of a eukaryotic cell.