Internal Organization of Cells and Nuclear Import and Export

Question 1

all cells have…

Answer 1

a plasma membrane and contain genetic material

Question 2

prokaryotes

Answer 2

lack a nucleus

include bacteria and archaeons

Question 3

eukaryotes

Answer 3

have a nucleus

include animals, plants, fungi, and protists

Question 4

in mammals…

Answer 4

cholesterol is present in cell membranes

choleserol belongs to a group of chemical compounds known as sterols → molecules containing hydroxyl group attached to a gour-ringed structure

Question 5

from an evolutionary perspective…

Answer 5

archaeons and ukaryotes are more closely related to each other than either is to bacteria

Question 6

nucleoid

prokaryotes

Answer 6

a discrete region of cell interior where DNA is concentrated; contains multiple loops formed from supercoils of DNA

prokaryotes

Question 7

plasmids

prokaryotes → bacteria

Answer 7

additional, small, circular moelcules of DNA carrying a small number of genes

prokaryotes → bacteria

Question 8

pili

prokaryotes → bacteria

Answer 8

a hollow, threadlike structure that connects bacteria allowing the transfer of plasmids via conjugation

prokaryotes → bacteria

Question 9

nucleus

eukaryotes

Answer 9

the compartment of the cell that houses DNA in chromosomes

eukaryotes

Question 10

nuclear membrane

eukaryotes

Answer 10

allos for more complex regulation of gene expression than is possible in prokaryotes

eukaryotes

Question 11

organelles

eukaryotes

Answer 11

compartements that divide the cell contents into smaller spaces with specialized functions; defined by their membranes

eukaryotes

Question 12

mitochondria

typical features of an animal cell

Answer 12

produces most of the ATP that serves as the energy currency of the cell

typical features of an animal cell

Question 13

plasma membrane

typical features of an animal cell

Answer 13

composed of phospholipids and proteins; regulates the passage of material into and out of the cell

typical features of an animal cell

Question 14

cytoskeleton

typical features of an animal cell

Answer 14

a network of protein fillaments and other associated proteins that provide the cell with an interal structural framework

typical features of an animal cell

Question 15

endoplasmic reticulum

typical features of an animal cell

Answer 15

involved in both protein and lipid synthesis

typical features of an animal cell

Question 16

lysomes

typical features of an animal cell

Answer 16

contain enzymes that break down macromolecules such as proteins, nucleic acids, lipids, and carbohydrates

typical features of an animal cell

Question 17

golgi apparatus

typical features of an animal cell

Answer 17

modifies and sorts proteins and lipids as they move to their final destinations in or out of the cell

typical features of an animal cell

Question 18

peroxisomes

typical features of an animal cell

Answer 18

break down speciifc organic molecules, such as fatty acids, and synthesize other organic molecules, such as cholesterol and some types of phospholipids

typical features of an animal cell

Question 19

cell wall

typical features of a plant cell

Answer 19

rigid barrier composed of polusaccharides

typical features of a plant cell

Question 20

chloroplasts

typical features of a plant cell

Answer 20

enable plant cells to harness the enrgy of sunlight to synthesize sugars

typical features of a plant cell

Question 21

plasmodesmata

typical features of a plant cell

Answer 21

connect neighboring plant cells

typical features of a plant cell

Question 22

vacuoles

typical features of a plant cell

Answer 22

contribute to the structural rigidity of plants by absorbing water and contributing to turgor pressure

typical features of a plant cell

Question 23

cytoplasm

Answer 23

the entire contents of a cell other than the nucleus

Question 24

cytosol

Answer 24

jelly-like internal environment of the cell that surrounds the organelles inside the plasma membrane

Question 25

nuclear envelope

Answer 25

encloses nuclear DNA and defines the nuclear compartment; separates nucleus and cytoplasm; formed from the inner and outer nuclear membrane (the outer membrane is continuous with the membrane of the ER)

Question 26

inner nuclear membrane

Answer 26

contains some small proteins; acts as binding sites for chomosomes; provides anchorage for the nuclear lamina

Question 27

nuclear lamina

Answer 27

finely woven meshwork of protein filaments that lines the inner face of the membrane and provides structural support for the nuclear envalope

Question 28

nuclear pore ## Footnote figure C

Answer 28

perforates the nuclear envalope in all eukaryotic cells; forms the gates through which molecules enter or leave the nucleus ## Footnote figure C

Question 29

nuclear localization signal (NLS)

Answer 29

the signal sequence that directs a protein from the cytosol into the nucleus; ususally consists of one or two short sequences containing several positively charged lysines or arginines

Question 30

nuclear import receptors

Answer 30

cytosolic proteins which recognize NLS; help direct newly synthesized proteins to a nuclear pore by interacting with fibrils that extend from the rim of the nuclear pore into the cytosol

Question 31

import/export of nuclear proteins ## Footnote figure D

Answer 31

rewuires energy provided by the hydrolysis of GTP ## Footnote figure D

Question 32

thylakoid membrane

Answer 32

third membrane found in chloroplasts

Question 33

nuclear pore complex

Answer 33

the only place where small polar molecules, ions, and macromolecules (proteins and RNAs) can travel between the nucleus and the cytoplasm

Question 34

Ran-GTP (importins)

Answer 34

molecule which carries a molecule of GTP and binds to inportin → changing its conformation and forcing it to release its cargo protein into the nucleus → the importin-Ran complex is then re-exported out through the nuclear pore

Question 35

Ran GAP (GTPase-activating protein)

Answer 35

stimulates ran to hydrolize its GTP to GDP → this causes Ran to release the importin back into the cytoplasm

Question 36

NTF2

Answer 36

GDP-Ran protein receptor which binds to GDP-Ran and transports it back through the nuclear pore into the nucleus

Question 37

Ran GEF (guanine nucleotide exchange factor)

Answer 37

stimulates Ran-GDP in the nucleus to release its GDP and pick up new GTP

Question 38

nuclear export signals (NES)

Answer 38

proteins targeted for export from the nucleus by specific amino acid sequences

Question 39

exportins

Answer 39

receptors within the nucleus who recognize NES and direct protein transport through the nuclear pore complex to the cytoplasm

Question 40

Ran-GTP (exportins)

Answer 40

promotes the formation of stable complexes between exportins and their cargo proteins; does the opposite for importins that their cargo; once in the cytoplasm GTP hydrolysis and relese of Ran-GDP leads to dissociation of the cargo protein which is released into the cytoplasm

Question 41

Ran-GDP (exportin)

Answer 41

recycles exportins through the nuclear pore complex to the nucleus for reuse