Chapter 4

Question 1

cell wall

Answer 1

a relatively thick layer of material that forms the periphery of all plant and fungal cells and many types of bacterial, archael, and protist cells

Question 2

central vacuole

Answer 2

a large, watery plant organelle whose functions include the maintenance of cell pressure, the storage of nutrients, and the retention and degradation of waste products

Question 3

chloroplasts

Answer 3

the organelle within plant and algae cells that is the site of photosynthesis

Question 4

cilia

Answer 4

hair-like extensions of a cell, composed of microtubules. Many cilia protrude from the surface of some cells, moving rapidly back and forth, serving to propel cells or to move material around it

Question 5

cytoplasm

Answer 5

the region of a cell inside the plasma membrane and outside the nucleus. Usually, this region is filled with the jelly-like cytosol containing the cell’s extranuclear organelles

Question 6

cytoskeleton

Answer 6

a network of protein filaments that functions in cell structure, cell movement, and the transport of materials within the cell. Microfilaments, intermediate filaments, and microtubules are all parts of the cytoskeleton

Question 7

cytosol

Answer 7

the protein-rich, jelly-like fluid in which a cell’s organelles that are outside the nucleus are immersed.

Question 8

endomembrane system

Answer 8

an interactive group of membrane-lined organelles and transport vesicles that functions within eukaryotic cells

Question 9

eukaryotic cell

Answer 9

a cell whose primary complement of DNA is contained within a membrane-lined nucleus. Eukaryotic cells have several other organelles in addition to the nucleus

Question 10

flagella

Answer 10

the relatively long, tail-like extensions of some cells, composed of microtubules, that function in cell movement

Question 11

gap junction

Answer 11

a protein assemblage that forms a communication channel between adjacent animal cells. Gap junctions open only as necessary as to allow small molecules and electrical signals to move between cells

Question 12

Golgi complex

Answer 12

a network of membranes, found in the cytoplasm of eukaryotic cells, that processes and distributes proteins that come to it from the rough endoplasmic reticulum

Question 13

intermediate filament

Answer 13

filaments of the cytoskeleton, intermediate in diameter between microfilaments and microtubules, that help stabilize the positions of the nucleus and other organelles within the cell

Question 14

lysosome

Answer 14

an organelle found in animal cells that digests worn-out cellular materials and foreign materials that enter the cell

Question 15

microfilament

Answer 15

the most slender of the eukaryotic cell’s cytoskeletal fibers, made of the protein actin and functioning in both cell movement and support

Question 16

micrograph

Answer 16

a picture taken with the aid of a microscope

Question 17

micrometer

Answer 17

a millionth of a meter, abbreviated by um

Question 18

microtubule

Answer 18

the largest of the cytoskeletal filaments, microtubules take the form of hollow tubes composed of the protein tubulin. They help give structure to the cell, serve as the “rails” on which transport vesicles move, and form the cellular extensions known as cilia and flagella

Question 19

mitochondria

Answer 19

organelles that are the primary sites of energy conversion within eukaryotic cells

Question 20

nanometer

Answer 20

a billionth of a meter; abbreviated nm

Question 21

nuclear envelope

Answer 21

the double membrane that lines the nucleus in eukaryotic cells

Question 22

nucleolus

Answer 22

the area within the nucleus of a cell devoted to the production of ribosomal RNA

Question 23

nucleus

Answer 23

a membrane-lined compartment that encloses the primary complement of DNA in eukaryotic cells

Question 24

organelle

Answer 24

a highly organized structure within a cell that carries out specific cellular functions. Almost all organelles are bound by membranes

Question 25

plasma membrane

Answer 25

a membrane forming the outer boundary of many cells, composed of a phospholipid bilayer interspersed with proteins and cholesterol molecules and coated, on its exterior face, with short carbohydrate chains associated with proteins and lipids

Question 26

plasmodesmata

Answer 26

channels in the plant cell wall that make possible communication between plant cells. Structure of these channels is such that the cytoplasm of one plant cell is continuous with that of another

Question 27

prokaryotic cell

Answer 27

a cell whose DNA is not located in the membrane-bound organelle known as a nucleus

Question 28

ribosome

Answer 28

an organelle, located in the cell’s cytoplasm, that is the site of protein synthesis. The translation phase of protein synthesis takes place within ribosomes

Question 29

rough endoplasmic reticulum

Answer 29

a network of membranes, found in the cytoplasm of eukaryotic cells, that aids in the processing of proteins

Question 30

smooth endoplasmic reticulum

Answer 30

a network of membranes within the eukaryotic cell that is the site of the synthesis of various lipids and site at which potentially harmful substances are detoxified

Question 31

transport vesicle

Answer 31

a membrane-lined sphere that moves within the cell’s endomembrane system, carrying within it proteins or other molecules