Chapter 4 Terms

Question 1

Micrograph

Answer 1

A photograph taken through a microscope

Question 2

Light Microscope (LM)

Answer 2

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 3

Cell Theory

Answer 3

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

Question 4

Electron Microscope (EM)

Answer 4

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 5

Scanning Electron Microscope (SEM)

Answer 5

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

Question 6

Transmission Electron Microscope (TEM)

Answer 6

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

Question 7

Prokaryotic Cell

Answer 7

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

Question 8

Eukaryotic Cell

Answer 8

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 9

Plasma Membrane

Answer 9

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 10

Chromosome

Answer 10

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 11

Ribosome

Answer 11

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 12

Cytoplasm

Answer 12

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

Question 13

Nucleoid

Answer 13

A dense region of DNA in a prokaryotic cell

Question 14

Flagella

Answer 14

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 15

Organelle

Answer 15

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

Question 16

Cellular Metabolism

Answer 16

The chemical activities of cells

Question 17

Nucleus

Answer 17

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

Question 18

Chromatin

Answer 18

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 19

Nuclear Envelope

Answer 19

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

Question 20

Nucleolus

Answer 20

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 21

Endomembrane System

Answer 21

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

Question 22

Vesicle

Answer 22

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

Question 23

Endoplasmic Reticulum (ER)

Answer 23

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

Question 24

Smooth Endoplasmic Reticulum

Answer 24

A network of interconnected membranous tubules in a eukaryotic cell’s cytoplasm. Smooth ER lacks ribosomes

Question 25

Rough Endoplasmic Reticulum

Answer 25

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 26

Glycoprotein

Answer 26

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

Question 27

Transport Vesicle

Answer 27

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 28

Golgi Apparatus

Answer 28

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

Question 29

Lysosome

Answer 29

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

Question 30

Vacuole

Answer 30

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

Question 31

Central Vacuole

Answer 31

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

Question 32

Peroxisome

Answer 32

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

Question 33

Mitochondria

Answer 33

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 34

Intermembrane Space

Answer 34

One of the two fluid-filled internal compartments of the mitochondrion. The intermembrane space is the narrow region between the inner and outer membranes

Question 35

Mitochondrial Matrix

Answer 35

The fluid contained within the inner membrane of a mitochondrion

Question 36

Chloroplast

Answer 36

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 37

Stroma

Answer 37

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 38

Thylakoid

Answer 38

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 39

Granum

Answer 39

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 40

Endosymbiosis

Answer 40

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 41

Cytoskeleton

Answer 41

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

Question 42

Microfilament

Answer 42

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 43

Intermediate Filament

Answer 43

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 44

Microtubule

Answer 44

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 45

Centriole

Answer 45

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 46

Cilia

Answer 46

A short cellular appendage specialized for locomotion formed from a core of nine outer doublet microtubules and two single microtubules covered by the cell's plasma membrane

Question 47

Basal Body

Answer 47

A eukaryotic cell organelle consisting of a 9 + 0 arrangement of microtubule triplets; may organize the microtubule assembly of a cilium or flagellum; structurally identical to a centriole

Question 48

Extracellular Matrix (ECM)

Answer 48

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

Question 49

Integrins

Answer 49

A transmembrane protein that interconnects the extracellular matrix and the cytoskeleton

Question 50

Cell Wall

Answer 50

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 51

Plasmodesmata

Answer 51

An open channel in a plant cell wall through which strands of cytoplasm connect from adjacent cells