Chapter 4 Organization of the cell

Question 1

Homeostasis

Answer 1

The balanced internal environment of the body; the automatic tendency of an organism to maintain
such a steady state.

Question 2

Cell theory

Answer 2

The scientific theory that the cell is the basic unit of life, of which all living things are composed, and that all cells are derived from pre-existing cells.

Question 3

plasma membrane

Answer 3

The selectively permeable surface membrane that encloses the cell contents and through which all materialsentering or leaving the cell must pass.

Question 4

organelles

Answer 4

One of the specialized structures within the cell, such as the mitochondria, Golgi complex, ribosomes, or contractile vacuole; many organelles are membrane-enclosed.

Question 5

microvilli

Answer 5

Minute projections of the plasma membrane that increase the surface area of the cell; found mainly in cells concerned with absorption or secretion, such as those lining the intestine or the kidney tubules.

Question 6

light microscope (LM),

Answer 6

• The optical microscope, often referred to as light microscope, is a type of microscope which uses visible light and a system of lenses to magnify images of small samples.
• Optical microscopes are the oldest design of microscope and were possibly invented in their present compound form in the 17th century.

Question 7

Magnification

Answer 7

Magnification is the process of enlarging something only in appearance, not in physical size.

Question 8

resolving power

Answer 8

The ability of a microscope to show fine detail, defi
ned as the minimum distance between two points at which they are seen as separate images; also called resolution.

Question 9

electron microscope (EM),

Answer 9

• A microscope capable of producing high resolution, highly magnified images through the use of an electronbeam (rather than light).

Question 10

transmission electron microscope (TEM)

Answer 10

Transmission electron microscopes (TEMs) produce images of thin sections;

Question 11

scanning electron microscope (SEM)

Answer 11

scanning electron microscopes
(SEMs) produce images of surfaces.

Question 12

Cell fractionation

Answer 12

The technique used to separate the components of
cells by subjecting them to centrifugal force.

Question 13

ultrastructure

Answer 13

The fine detail of a cell, generally only observable by
use of an electron microscope.

Question 14

cell homogenate

Answer 14

uniform in composition or character (i.e. color, shape, size, weight, height, distribution, texture, language, disease, temperature, etc.)

Question 15

centrifuge

Answer 15

A device used to separate cells or their components by
subjecting them to centrifugal force.

Question 16

differential centrifugation

Answer 16

is a common procedure used to separate certain organelles from whole cells for further analysis of specific parts of cells.

Question 17

density gradient centrifugation

Answer 17

Involves the centrifugation of material through a centrifugation medium of higher or graded density. When exposed to a elevated centrifugal force, cellular components migrate through the medium and separate based on their density.

Question 18

prokaryotic cells

Answer 18

A cell that lacks a nucleus and other membrane-enclosed organelles; includes the bacteria and archaea

(kingdoms Bacteria and Archaea)

Question 19

eukaryotic cells

Answer 19

An organism whose cells have nuclei
and other membrane-enclosed organelles. Includes protists, fungi,
plants, and animals.

Question 20

nucleoid

Answer 20

Region of a prokaryotic cell that contains DNA; not
enclosed by a membrane.

Question 21

cell walls

Answer 21

The structure outside the plasma membrane of certain cells; may contain cellulose (plant cells), chitin (most fungal cells), peptidoglycan and/or lipopolysaccharide (most bacterial cells), or other material.

Question 22

flagella

Answer 22

• A long, whiplike structure extending from certain cells and used in locomotion.
• 9x2 arrangement of microtubules is characteristic of virtually all eukaryotic cilia and fl agella.

Question 23

ribosomes

Answer 23

Organelles that are part of the protein synthesis machinery of both prokaryotic and eukaryotic cells; consist of a larger and smaller subunit, each composed of ribosomal RNA (rRNA) and ribosomal proteins.

Question 24

cytoplasm

Answer 24

The plasma membrane and cell contents with the exception of the nucleus.

Question 25

nucleoplasm

Answer 25

The contents of the cell nucleus.

Question 26

cytosol

Answer 26

The fluid component of the cytoplasm in which the organelles are suspended.

Question 27

endomembrane system

Answer 27

The group of membranous structures in eukaryotic cells that interact through direct connections by vesicles; includes the endoplasmic reticulum, outer membrane of the nuclear envelope, Golgi complex, lysosomes, and the plasma membrane;

Question 28

vesicles

Answer 28

Any small sac, especially a small, spherical, membrane-enclosed compartment, within the cytoplasm.

Question 29

nucleus

Answer 29

(2) A cell organelle in eukaryotes that contains the DNA and serves as the control center of the cell.

Question 30

regeneration

Answer 30

The process of renewal, restoration, and growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage.

Question 31

DNA

Answer 31

Double-stranded nucleic acid; contains genetic information coded in specifi c sequences of its constituent nucleotides.

Question 32

nuclear envelope

Answer 32

The double membrane system that encloses the cell nucleus of eukaryotes.

Question 33

nuclear pores

Answer 33

Structures in the nuclear envelope that allow passage of certain materials between the cell nucleus and the cytoplasm.

Question 34

nuclear lamina

Answer 34

A dense (~30 to 100 nm thick) fibrillar network inside the nucleus of most cells.

Question 35

replication

Answer 35

The process by which DNA is duplicated; ordinarily a semiconservative process in which a double helix gives rise totwo double helices, each with an “old” strand and a newly synthesized strand.

Question 36

genes

Answer 36

A segment of DNA that serves as a unit of hereditary information; includes a transcribable DNA sequence (plus associated sequences regulating its transcription) that yields a protein or RNA product with a specific function.

Question 37

messenger RNA (mRNA)

Answer 37

RNA that specifi es the amino acid sequence of a protein; transcribed from DNA

Question 38

chromatin

Answer 38

The complex of DNA and protein that makes up eukaryotic chromosomes.

Question 39

chromosomes

Answer 39

Structures in the cell nucleus that consist of chromatin and contain the genes. The chromosomes become visible under the microscope as distinct structures during cell division.

Question 40

nucleoli

Answer 40

Specialized structure in the cell nucleus formed from regions of several chromosomes; site of assembly of the ribosomal subunits.

Question 41

nucleolar organizer

Answer 41

a chromosomal region around which the nucleolus forms. This region is the particular part of a chromosome that is associated with a nucleolus after the nucleus divides.

Question 42

endoplasmic reticulum

Answer 42

An interconnected network of internal membranes in eukaryotic cells enclosing a compartment, the ER lumen. Rough ER has ribosomes attached to the cytosolic surface; smooth ER, a site of lipid biosynthesis, lacks ribosomes.

Question 43

ER lumen

Answer 43

The lumen of the endoplasmic reticulum (ER) is the area enclosed by the endoplasmic reticulum membrane

Question 44

Smooth ER

Answer 44

The smooth endoplasmic reticulum has functions in several metabolic processes. It synthesizes lipids, phospholipids, and steroids.

Question 45

rough ER

Answer 45

the rough endoplasmic reticulum (often abbreviated RER or Rough ER) (also called ergastoplasm) is studded with protein-manufacturing ribosomes giving it a "rough" appearance (hence its name)

Question 46

molecular chaperones

Answer 46

Proteins that help other proteins fold properly. Although not dictating the folding pattern, chaperones make the process more efficient.

Question 47

proteasomes

Answer 47

A large multiprotein structure that recognizes and degrades protein molecules tagged with ubiquitin into short, nonfunctional peptide fragments

Question 48

transport vesicle

Answer 48

Small cytoplasmic vesicles that move substances from one membrane system to another.

Question 49

Golgi complex

Answer 49

Organelle composed of stacks of fl attened, membranous sacs. Mainly responsible for modifying, packaging, and sorting proteins that will be secreted or targeted to other organelles of the internal membrane system or to the plasma membrane; also called Golgi body or Golgi apparatus.

Question 50

cisternae

Answer 50

Stacks of flattened membranous sacs that make up the Golgi complex.

Question 51

Lysosomes

Answer 51

Intracellular organelles present in many animal cells; contain a variety of hydrolytic enzymes.

Question 52

vacuole

Answer 52

A fluid-filled, membrane-enclosed sac found within the cytoplasm; may function in storage, digestion, or water elimination

Question 53

tonoplast

Answer 53

The membrane surrounding a vacuole.

Question 54

contractile vacuoles

Answer 54

A membrane-enclosed organelle found in certain freshwater protists, such as Paramecium; appears to have an osmoregulatory function

Question 55

Peroxisomes

Answer 55

In eukaryotic cells, membrane enclosed organelles containing enzymes that produce or degrade hydrogen peroxide.

Question 56

Serial endosymbiosis

Answer 56

The hypothesis that certain organelles such as mitochondria and chloroplasts originated as symbiotic prokaryotes that lived inside other, free-living prokaryotic cells

Question 57

mitochondria

Answer 57

Intracellular organelles that are the sites of oxidative phosphorylation in eukaryotes; include an outer membrane and an inner membrane.

Question 58

aerobic respiration

Answer 58

In aerobic respiration the terminal electron acceptor is molecular oxygen; in anaerobic respiration the terminal acceptor is an inorganic molecule other than oxygen.

Question 59

intermembrane space

Answer 59

the region between the inner membrane and the outer membrane of a mitochondrion or a chloroplast. The main function of the intermembrane space is oxidative phosphorylation

Question 60

outer mitochondrial membrane

Answer 60

The outer mitochondrial membrane, which encloses the entire organelle, is 60 to 75 angstroms (Å) thick. It has a protein-to-phospholipid ratio similar to that of the eukaryotic plasma membrane (about 1:1 by weight).

Question 61

inner mitochondrial membrane

Answer 61

is the mitochondrial membrane which separates the mitochondrial matrix from the intermembrane space.

Question 62

cristae

Answer 62

Shelflike or fingerlike inward projections of the inner membrane of a mitochondrion

Question 63

apoptosis

Answer 63

Programmed cell death; apoptosis is a normal part of an organism’s development and maintenance.

Question 64

necrosis

Answer 64

Uncontrolled cell death that causes infl ammation and damages other cells

Question 65

caspases

Answer 65

Any of a group of proteolytic enzymes that are active in the early stages of apoptosis

Question 66

free radicals

Answer 66

Toxic, highly reactive compounds with unpaired electrons that bond with other compounds in the cell and interfere with normal function

Question 67

photosynthesis

Answer 67

Th e biological process that captures light energy and transforms it into the chemical energy of organic molecules (e.g., carbohydrates), which are manufactured from carbon dioxide and water.

Question 68

Chloroplasts

Answer 68

Membranous organelles that are the sites of photosynthesis in eukaryotes; occur in some plant and algal cells.

Question 69

chlorophyll

Answer 69

A group of light-trapping green pigments found in most photosynthetic organisms

Question 70

carotenoids

Answer 70

A group of yellow to orange plant pigments synthesized from isoprene subunits; include carotenes and xanthophylls

Question 71

stroma

Answer 71

A fl uid space of the chloroplast, enclosed by the chloroplast inner membrane and surrounding the thylakoids; site of the reactions of the Calvin cycle

Question 72

thylakoids

Answer 72

An interconnected system of fl att ened, saclike, membranous structures inside the chloroplast.

Question 73

grana

Answer 73

A stack of thylakoids within a chloroplast.

Question 74

plastids

Answer 74

A family of membrane-enclosed organelles occurring in photosynthetic eukaryotic cells; include chloroplasts, chromoplasts, and amyloplasts and other leukoplasts.

Question 75

proplastids

Answer 75

Organelles that are plastid precursors; may mature into various specialized plastids, including chloroplasts, chromoplasts, or leukoplasts.

Question 76

Chromoplasts

Answer 76

Pigment-containing plastids; found mainly in fl owers and fruits.

Question 77

Leukoplasts

Answer 77

Colorless plastids; include amyloplasts, which are used for starch storage in cells of roots and tubers

Question 78

cytoskeleton

Answer 78

The dynamic internal network of protein fibers that includes microfilaments, intermediate filaments, and microtubules.

Question 79

Microtubules

Answer 79

Hollow, cylindrical fibers consisting of tubulin protein subunits; major components of the cytoskeleton and found in mitotic spindles, cilia, flagella, centrioles, and basal bodies.

Question 80

tubulin

Answer 80

proteins that make up microtubules in eukaryotic cells.

Question 81

Microtubule-associated proteins (MAPs)

Answer 81

Include structural proteins that help regulate microtubule assembly and cross-link microtubules to other cytoskeletal polymers; and motors, such as kinesin and dynein, that use ATP to produce movement.

Question 82

kinesin

Answer 82

Is a protein belonging to a class of motor proteins found in eukaryotic cells. Kinesins move along microtubule (MT) filaments, and are powered by the hydrolysis of adenosine triphosphate (ATP) (thus kinesins are ATPases).

Question 83

Dynein

Answer 83

a motor protein (also called molecular motor or motor molecule) in cells which converts the chemical energy contained in ATP into the mechanical energy of movement.

Question 84

microtubule-organizing centers | (MTOCs)

Answer 84

The region of the cell from which microtubules are anchored and possibly assembled. The MTOCs of many organisms (including animals, but not fl owering plants or most gymnosperms) contain a pair of centrioles.

Question 85

centrosome

Answer 85

An organelle in animal cells that is the main microtubule-organizing center; typically contains a pair of centrioles and is important in cell division.

Question 86

centrioles

Answer 86

* One of a pair of small, cylindrical organelles lying at right angles to each other near the nucleus in the cytoplasm of animal cells and certain protist and plant cells. * They are known as 9 × 3 structures because they consist of nine sets of three att ached microtubules arranged to form a hollow cylinder

Question 87

mitotic spindle

Answer 87

Structure consisting mainly of microtubules that provides the framework for chromosome movement during cell division.

Question 88

cilia

Answer 88

One of many short, hairlike structures that project from the surface of some eukaryotic cells and are used for locomotion or movement of materials across the cell surface.

Question 89

basal body

Answer 89

Structure involved in the organization and anchorage of a cilium or flagellum. Structurally similar to a centriole; each is in the form of a cylinder composed of nine triplets of microtubules (9 × 3 structure).

Question 90

primary cilium

Answer 90

primary cilia are found on nearly every cell in the body

Question 91

Microfilaments

Answer 91

Thin fibers consisting of actin protein subunits; form part of the cytoskeleton.

Question 92

cell cortex

Answer 92

is a specialized layer of cytoplasmic protein on the inner face of the plasma membrane of the cell periphery. It functions as a modulator of plasma membrane behavior and cell surface properties.

Question 93

myosin

Answer 93

A protein that together with actin is responsible for muscle contraction.

Question 94

pseudopodia

Answer 94

A temporary extension of an amoeboid cell that is used for feeding and locomotion.

Question 95

glycocalyx

Answer 95

A coating on the outside of an animal cell, formed by the polysaccharide portions of glycoproteins and glycolipids associated with the plasma membrane.

Question 96

extracellular matrix (ECM)

Answer 96

A network of proteins and carbohydrates that surrounds many animal cells.

Question 97

fibronectins

Answer 97

Glycoproteins of the extracellular matrix that bind to integrins (receptor proteins in the plasma membrane).

Question 98

Integrins

Answer 98

Receptor proteins that bind to specifi c proteins in the extracellular matrix and to membrane proteins on adjacent cells; transmit signals into the cell from the extracellular matrix.

Question 99

middle lamella

Answer 99

The layer composed of pectin polysaccharides that serves to cement together the primary cell walls of adjacent plant cells.