Chapter 6 - A Tour of the Cell

Question 1

define cell theory

Answer 1

all living things are composed of cells and the products of cells; all cells come only from pre-existing cells via cell division

Question 2

list three types of microscopes

Answer 2

light, transmission, and scanning electron microscopes

Question 3

prokaryotic cell size vs eukaryotic cell size

Answer 3

prokaryotic cells are significantly smaller than eukaryotic cells

Question 4

why are cells so small?

Answer 4

surface area becomes a limiting factor

Question 5

describe prokaryotic cells

Answer 5

“small and simple”; lack a nucleus, ribosomes and cell wall differ from those of eukaryotes; capsule: sticky outer coat; fimbriae projections

Question 6

describe eukaryotic cells

Answer 6

(eukaryotes: animals, plants, fungi, protists) cells contain membrane-bounded organelles and membranous structures; most cells are small

Question 7

define organelles

Answer 7

the site of cellular metabolism; they increases membrane area

Question 8

what is the role of the nucleus?

Answer 8

stores, protects, replicates, and expresses genetic information - often the largest organelle

Question 9

define nuclear envelope

Answer 9

double membrane around the nucleus (the space between membranes is the perinuclear space)

Question 10

define nucleoplasm

Answer 10

contains chromatin (DNA and protein) and one or more nucleoli (for ribosome synthesis)

Question 11

define nuclear lamina

Answer 11

near the inner nuclear membrane; gives shape to the nucleus; consists of proteins called lamins

Question 12

define nuclear matrix

Answer 12

framework of fibres throughout the nucleus

Question 13

describe ribosomes

Answer 13

one of the required components necessary for the synthesis of protein; two subunits, composed of proteins and ribosomal RNA (rRNA); not surrounded by membrane; may be free or bound to ER

Question 14

what do free ribosomes do?

Answer 14

located in cytosol; make proteins that will be active in cytosol, chloroplast, mitochondrion, nucleoplasm, peroxisomes

Question 15

what do bound ribosomes do?

Answer 15

bound to the ER, make proteins that will be active in endomembrane system and extracellular areas

Question 16

define the endomembrane system

Answer 16

a system of membranes whose members are in direct contact with one another or which engage in vesicular traffic with one another

Question 17

what is part of the endomembrane system?

Answer 17

nuclear envelope, ER, golgi apparatus, vesicles, lysosomes, vacuoles, plasma membrane

Question 18

define endoplasmic reticulum (ER)

Answer 18

a network of tubes and sacs

Question 19

define smooth ER and its role

Answer 19

lacks bound ribosomes, functions include: lipid synthesis, carbohydrate metabolism, detoxifies many drugs and poisons

Question 20

define rough ER and its role

Answer 20

has bound ribosomes, functions include: protein synthesis, protein sorting, protein modification, membrane biogenesis

Question 21

define golgi apparatus

Answer 21

a series of flattened sacs and associated vesicles; contains cis and trans cisternae (cis golgi network is receiving; trans golgi network is shipping)

Question 22

golgi apparatus roles

Answer 22

protein sorting, protein processing, addition and modification of olgiosaccharides to glycoproteins and glycolipids, biogenesis of lysosomes

Question 23

define vesicles and their role

Answer 23

transport substances from one part of the endomembrane system to another; arise as part of the endomembrane system; motor proteins move vesicles along microtubule tracks

Question 24

define lysosomes

Answer 24

compartments in animal cells that contain acid hydrolases; maintain and acidic pH of 5

Question 25

define heterophagy

Answer 25

digestion of material brought into the cell from the environment

Question 26

define autophagy

Answer 26

digestion of the cells own materials

Question 27

list the functions of vacuoles

Answer 27

occupies space (holds water and provides cheap growth to the plant); performs hydrolytic functions; important in maintaining cell turgor pressure; stores various substances

Question 28

define central vacuole

Answer 28

quite large, occupying most of the volume of mature plant cells and many fungal cells

Question 29

define mitochondria

Answer 29

sites of cellular respiration: perform most of the oxidations that provide energy in the form of ATP for the cell

Question 30

describe mitochondria and their functions

Answer 30

double membrane; inner mitochondrial membrane; mitochondrial matrix (site of the citric acid cycle); its own circular DNA; multiply by binary fission; incapable of independent existence

Question 31

define and describe chloroplasts

Answer 31

types of plastids that perform photosynthesis in plants and algae - green due to chlorophyll; double membrane; thylakoids may be stacked; circular DNA; multiply by binary fission

Question 32

define thylakoid membrane

Answer 32

site of light absorption and light-induced electron transport that produces ATP and NADPH

Question 33

define stroma

Answer 33

site of the Calvin cycle

Question 34

define chemiosmosis

Answer 34

energy coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP

Question 35

what is the endosymbiotic theory?

Answer 35

chloroplasts and mitochondria arose two billion years ago from bacteria that were engulfed by early eukaryotic cells

Question 36

define peroxisomes and their roles

Answer 36

belong to a group of organelles collectively called microbodies; single membrane; involved in various catabolic oxidative processes that remove hydrogen from organic molecules and transfer it to O2, forming hydrogen peroxide; not part of the endomembrane system

Question 37

define the cytoskeleton

Answer 37

contitutes the "bones and muscles" of the cell; extensive, dynamic network of protein filaments and associated proteins in eukaryotic cells

Question 38

list the functions of the cytoskeleton

Answer 38

support, organization, motility (holds organelles in place, maintains and changes cell shape, transmits signals from cell surface to cell interior)

Question 39

list the components of the cytoskeleton

Answer 39

microtubules, microfilaments, intermediate filaments (all made of proteins)

Question 40

describe microtubules (MTs)

Answer 40

hollow fibres 25nm in diameter; dynamic: can polymerize, depolymerize, or remain stable

Question 41

define microtubule organizing centers (MTOCs)

Answer 41

nucleation sites for polymerization

Question 42

what motor proteins are associated with MTs?

Answer 42

dyneins and kinesins (they "walk" along MTs in an ATP-dependent manner, which can generate "sliding" effects between adjacent MTs, and can carry cargo along MTs)

Question 43

where do dyneins move their cargo along MTs?

Answer 43

toward the cell center

Question 44

where do kinesins move their cargo along MTs?

Answer 44

away from the cell center

Question 45

define microfilaments

Answer 45

polymerized actin molecules (solid rods of 7nm diameter) - the associated motor proteins are myosins

Question 46

list the roles if microfilaments

Answer 46

structural support of cells and cell extensions, cell crawling, cycloisis (movement of cytoplasm in the cell)

Question 47

define intermediate filaments

Answer 47

a diverse group of filaments 8-12nm in diameter; tough, durable fibres involved in support function only, extensive network in cytosol

Question 48

define plant cell walls

Answer 48

cellulose microfibrils in a matrix of other polysaccharides and proteins

Question 49

list the functions of cell walls

Answer 49

protection, maintenance of shape, prevention of excess water uptake

Question 50

describe the animal cell surface

Answer 50

intercellular junctions; tight junctions (diffusion barrier), desmosomes (anchoring junctions), gap junctions (communication junctions)

Question 51

describe the extracellular matrix (ECM)

Answer 51

glycoproteins, proteoglycans, and other proteins cross-linked to one-another by extracellular adhesion proteins

Question 52

how is the ECM connected to the plasma membrane

Answer 52

linked via cell adhesion molecules (CAMs)

Question 53

list the functions of the ECM

Answer 53

anchorage, support, tissue formation, gene expression