Chapter 6: A Tour of the Cell

Question 1

Cytosol

Answer 1

semifluid, jellylike substance which subcellular components are suspended

Question 2

Eukaryotic Cell

Answer 2

most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane

Question 3

Prokaryotic Cell

Answer 3

DNA is concentrated in a region that is not membrane-enclosed aka nucleoid

Question 4

Cytoplasm

Answer 4

region between the nucleus and the plasma membrane; suspended in cytosol are a variety of organelles of specialized form and function

Question 5

Plasma Membrane

Answer 5

a selective barrier that allows passage of enough oxygen, nutrients, and wastes to service entire cell; bilayer of phospholipids

Question 6

Nucleus

Answer 6

contains most of the genes (some genes are located in mitochondria and chloroplasts)

Question 7

Nuclear Envelope

Answer 7

double membrane (each a lipid bilayer with associated proteins), are separated by a space of 20-40 nm

Question 8

Pore Complex

Answer 8

large protein assembly that spans nucleur envelop and plays an important role in the cell by regulating the entry and exit of molecules from nucleus

Question 9

Nuclear Lamina

Answer 9

a netlike array of protein filaments that maintains shape of the nucleus by mechanically supporting nuclear envelope

Question 10

Chromatin

Answer 10

the complex of DNA and proteins making up chromosomes

Question 11

Nucleolus

Answer 11

structure within nucleus where ribosomal RNA (rRNA) is synthesized from instructions of DNA; proteins from cytoplasm are assembled with rRNA into large and small subunits of ribosomes

Question 12

Ribosomes

Answer 12

complexes made of ribosomal RNAs and proteins; the cellular components that carry out protein synthesis

Question 13

Free Ribosomes

Answer 13

make proteins that function within the cytosol

Question 14

Bound Ribosomes

Answer 14

make proteins that are destined for insertion into membranes, for packaging within certain organelles such as lysosomes or for export from the cell

Question 15

Endomembrane System

Answer 15

different membrane-bound organelles (nuclear envelope, the endoplasmic reticulum, Golgi apparatus, lysosomes, various kinds of vesicles and vacuoles, and plasma membrane) that are related through direct physical continuity or by transfer of membrane segments as tiny vesicles

Question 16

Vesicles

Answer 16

sacs made of membranes

Question 17

Endoplasmic Reticulum (ER)

Answer 17

cisternae = tubules and sacs reservoir for liquid; ER lumen = cisternal space separate from cytosol; continuous with nuclear envelope = continuous with lumen; smooth/rough ER

Question 18

Smooth ER Function

Answer 18

enzymes of smooth ER: synthesize lipids i.e. oils & steroids), and new membrane phospholipids

Question 19

Rough ER (secretory proteins)

Answer 19

1. polypeptide chain grows from bound ribosome;
2. chain thread into ER lumen through pore formed by protein complex in ER membrane and chain folds into functional shape as it enters ER
3. carbohydrates are attached to proteins (glycoproteins) in ER lumen by enzymes built in membrane; ER keeps separate from proteins in cytosol
4. secretory proteins depart from ER wrapped in membranes through transitional ER

Question 20

Glycoprotein

Answer 20

proteins with carbohydrates covalently bond to them

Question 21

Rough ER Membrane Factory

Answer 21

1. polypeptides destined to be membrane proteins grow from ribosomes
2. chains are inserted into the ER membrane itself and enzymes built into ER membrane assemble phospholipids from precursors in the cytosol
3. ER membrane expands, and portions of it are transferred in transport vesicles to other components of endomembrane system

Question 22

Golgi Apparatus Function

Answer 22

1. “receive” vesicles to the cis face (on the same side) from ER [vesicle from ER can add its membrane w/contents by fusing with Golgi membrane]
2. “sort” products of ER are modified (i.e. glycoproteins have carbohydrates modified) and targeted for various parts of cell
3. “ship” trans face (on the opposite side) gives rise to vesicles that pinch off and travel to other sites

Question 23

Lysosome

Answer 23

membranous sac of hydrolytic enzymes that are used to digest (hydrolyze) macromolecules; made by rough ER and transferred to Golgi apparatus for further processing

Question 24

Phagocytosis

Answer 24

1. a type of endocytosis in which large particulate substances or small organisms are taken up by a cell (i.e. amoeba engulfing smaller organisms or food particles)
2. lysosomes digest (hydrolyze) materials taken into the cell

Question 25

Autophagy

Answer 25

1. a damaged organelle or small amount of cytosol becomes surrounded by a double membrane 2. lysosome fuses with the outer membrane of this vesicle 3. lysosomal enzymes dismantle the inner membrane with enclosed material 4. remaining small organic compounds are released to cytosol for reuse (cell continually renews itself)

Question 26

Vacuole

Answer 26

large vesicles derived from ER and Golgi apparatus selective in transporting solutes/differs in composition from the cytosol; integral part of a cell's endomembrane system

Question 27

Food Vacuole

Answer 27

a membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell

Question 28

Contractile Vacuoles

Answer 28

a membranous sac that helps move excess water out of certain freshwater protists

Question 29

Central Vacuole

Answer 29

mature plant cells develop by the coalescence of smaller vacuoles; solution inside is plan cell's main repository of inorganic ions

Question 30

Endosymbiont Theory

Answer 30

Early ancestor of eukaryotic cell engulfed an oxygen using non-photosynthetic/photosynthetic prokaryotic cell; formed a relation with the host cell --->host cell and its endosymbiont (cell within a cell) merged into a single organism

Question 31

Mitochondria

Answer 31

cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, and other fuels

Question 32

Cristae

Answer 32

convoluted inner membrane with foldings of mitochondrion that increase surface area of inner membrane for increase ATP production

Question 33

Mitochondrial Matrix

Answer 33

enclosed by the inner membrane; contains many different enzymes and mitochondrial DNA and ribosomes; enzymes catalyze some steps of cellular respiration (ATP)

Question 34

Chloroplasts

Answer 34

converts solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from CO2

Question 35

Thylakoids

Answer 35

another membranous system flattened and interconnected sacs inside chloroplast

Question 36

Granum

Answer 36

thylakoids stacked like poker chips

Question 37

Stroma

Answer 37

fluid outside the thylakoids which contains the chloroplast DNA, ribosomes and enzymes

Question 38

Peroxisome

Answer 38

bounded by a single membrane that remove hydrogen atoms from various substrates and transfer them to oxygen (function example = break fatty acids down into smaller molecules for mitochondria to use as fuel in cellular respiration)

Question 39

Cytoskeleton

Answer 39

network of fibers extending through the cytoplasm

Question 40

Cytoskeleton Function

Answer 40

1. mechanical support to the cell and maintain its shape 2. cell motility: works together with motor proteins and plasma membrane to allow cells to move along fibers 3. manipulates the plasma membrane, bending it inward to form food vacuoles or other phagocytic vesicles

Question 41

Microtubules

Answer 41

hollow tubes; tubulin (globular proteins), maintenance of cell shape/compression resistant girders; cell motility (i.e. cilia or flagella);chromosome movements in cell division; organelle movements; guide vesicles ER to Golgi to plasma membrane

Question 42

Centrosome

Answer 42

area near nucleus where microtubules grow out

Question 43

Centrioles

Answer 43

pair made of nine sets of three microtubules each with non-tubulin proteins that connect; set at right angle from each other

Question 44

Flagella

Answer 44

microtubule containing extensions that project from some cells sheathed in an extension of plasma membrane; undulating motion like tail of a fish

Question 45

Cilia

Answer 45

microtubule containing extensions that project from some cells sheathed in an extension of plasma membrane; alternating power and recovery strokes like oars; signal receiving antenna for cell

Question 46

Basal Body

Answer 46

structurally very similar to a centriole within flagella/cilia

Question 47

Dyneins

Answer 47

large motor proteins that are attached along each outer microtubule doublet that has two feet that walk using ATP for energy

Question 48

Microfilaments

Answer 48

2 intertwined strands of actin (globular protein); maintenance of shape/tension bearing elements of pulling forces; changes in cell shape; muscle contraction; cytoplasmic streaming in plant cells; cell motility (amoeboid movement); division of animal cells

Question 49

Cortex

Answer 49

microfilaments gives the outer cytoplasmic layer of a cell the semisolid consistency of a gel in contrast with the more fluid state of interior cytoplasm

Question 50

Myosin

Answer 50

protein that interacts with microfilament interact to cause muscle contractions

Question 51

Pseudopodia

Answer 51

cell crawls along a surface by extending cellular extension and moving toward them

Question 52

Cytoplasmic Streaming

Answer 52

actin protein interaction contribute to a circular flow of cytoplasm within cells

Question 53

Intermediate Filaments

Answer 53

fibrous proteins coiled into cables (made of several different proteins); cell shape/tension bearing elements of pulling forces; anchorage of nucleus and certain other organelles; formation of nuclear lamina

Question 54

Extracellular Matrix

Answer 54

1. Collage fibers (glycoproteins) 2. Proteoglycans molecules attached to noncovalently to single long polysaccharide molecule 3. Integrins bind to ECM on outside and attached to microfilaments on inside; transmit signals from cell exterior to interior resulting changes in cell behavior

Question 55

Plant Cell Wall

Answer 55

1. Primary cell wall = microfibrils made of polysaccharide cellulose/thin and flexible 2. Secondary cell wall between primary and plasma membrane (deposited in several laminated layers; very durable)

Question 56

Plasmodesmata (Plants)

Answer 56

cell walls are perforated with channels that connect cells so water and small solutes pass freely

Question 57

Junctions (Animal)

Answer 57

Tight: plasma membranes tightly pressed together = water tight seal Desmosomes: like rivets fastening cells together (anchored to intermediate filaments) Gap: cytoplasmic channels from cell to another -- membrane proteins surrounding pores which ions, sugars, amino acids and other small molecules pass (important in heart muscle)