organelles part 1

Question 1

what is the purpose of centrifugation

Answer 1

to separate cellular components based on density or sediment coefficiant

Question 2

what is the endosymbiont theory

Answer 2

theory that mitochondria arose from an aerobic prokaryotic cell bacterium being taken up by an anerobic pre-eukaryotic cell (explains why mitochondria is double membraned and has own set of DNA and replication cycles)

Question 3

what is the interior space of most organelles made of

Answer 3

similar to the extracellular space

Question 4

nucleus general characetristics

Answer 4

contains almost all of DNA in eukaryotic cell
site of DNA replication, RNA transcription, RNA processing and ribosome assembly
surrounded by nuclear envelope that is continuous with ER

Question 5

histones and nucleosomes

Answer 5

“beads on a string”
compact DNA, help it fit in smaller space
nucleosome is bead
histone is string

Question 6

DNA from smallest to largest

Answer 6

1. DNA double helix
2. nucleosomes (beads on a string)
3. chromatin fiber
4. looped domains
5. heterochromatin
6. chromosome

Question 7

what is heterochromatin

Answer 7

tightly packed DNA, proteins less accessible and less likely to be expressed

Question 8

euchromatin

Answer 8

lightly packed DNA, proteins more accessible and more likely to be expressed

Question 9

what is epigenetic?

Answer 9

heritable traits but no genetic mutations

ex. you can’t inherit cancer but you can inherit predispositions that make cancer more likely

Question 10

how does the nuclear pore complex affect permeability of the nucleus

Answer 10

small molecules can move freely in and out but larger molecules must be actively transported (gated transport)

Question 11

nuclear transport: import cycle

Answer 11

1. importin binds cargo
2. importin/cargo exits through NPC
3. GTP bound ran binds to importin
4. cargo pops off into the nucleus
5. GTP/ran/importin exits nucleus
6. GAP hydrolyses GTP/Ran to GDP and leaves importin

Question 12

nuclear transport: export cycle

Answer 12

1. exportin binds Ran/GTP
2. exportin/Ran/GTP binds to cargo
3. exportin/ran/gtp/cargo exits nucleus
4. GAP hydrolyses GTP/ran to GDP and cargo pops off into cytosol

Question 13

when is Ran considered”on” and “off” ?

Answer 13

ON–> when bound to GTP
OFF–> when bound to GDP
converted by GAP

Question 14

what is the nuclear lamina

Answer 14

gives nuclear envelope structure and shape
anchored to nuclear protein complex and integral membrane proteins
made up of nuclear lamins (intermediate filaments)

Question 15

how does the nucleus know where to reform during mitosis?

Answer 15

it can sense the cloud of GTP bound ran surrounding the nucleus
DNA associates with GEF

Question 16

general characteristics of ER

Answer 16

continuous with nucleus
important for intracellular Ca2 storage
production of transmembrane proteins/lipids
makes proteins destined for secretion

Question 17

rough ER

Answer 17

contains ribosomes embedded in ER
site of protein production, modification and lipid synthesis
(proteins are able to be translocated as they are translated)

Question 18

smooth ER

Answer 18

not associated with ribosomes
involved in lipid metabolism and detoxification of lipid soluble drugs
important for intracellular Ca2 storage

Question 19

what are the ways proteins can be imported

Answer 19

co translational translocation
- protein built as it is being moved across ER
post translational translocation
- protein is built and then moved across membrane

Question 20

general characteristics of Golgi body

Answer 20

series of separate flattened sacs
major site of carbohydrate synthesis
sorts and dispatches proteins from the ER
attaches carbohydrates to proteins and lipids
modifies proteins
important for tracking and directing

Question 21

how does Golgi transport work

Answer 21

pinches off vesicles from Golgi in order to ensure protein is not exposed to hydrophilic cytosol and fuses with membrane to release contents