Lecture 5- eukaryotic cell structure

Question 1

origin of eukaryotes = the _____ hypothesis

Answer 1

endosymbiotic

good roommate

Question 2

describe the ‘good roommate’ hypothesis

Answer 2

• heterotrophic bacteria are sensitive to increasing [O2]
• eukaryotes evolved O2 neutralizing enzymes
• bacteria ingested but not digested… these became organelles mitochondria and chloroplast

Question 3

endomembrane system=

Answer 3

membrane-bound organelles that arose from infoldings of membrane and are connected via vesicles

Question 4

vesicle=

Answer 4

membrane-bound compartment that contains cargo

Question 5

list the 4 organelles in endomembrane system

Answer 5

• outer nuclear membrane
• ER
• golgi
• lysosome

Question 6

nucleus/ nucleolus city analogy:
____ is the whole city, ____ is downtown
(they are not physically separate)

Answer 6

nucleus

nucleolus

Question 7

the nucleus stores ___ and is the site of ___ _____

Answer 7

DNA

gene expression

Question 8

the ___ is double-membrane bound with the outer membrane continuous with the ___

Answer 8

nucleus

ER

Question 9

What does the NPC (nuclear pore complex) do?

Answer 9

transmembrane complexes that span both bilayers

- allows nonspecific transport

Question 10

____ is the site of ribosomal subunit assembly

- subunits associate with their rRNAs at the ____

Answer 10

nucleolus

nucleolus

Question 11

ribosomal subunits leave the nucleus as independent subunits and come together in the ____ during ____

Answer 11

cytoplasm

translation

Question 12

the nuclear envelope includes both nuclear membranes

• function:
• structure:

Answer 12

fxn= protects DNA
structure = 2 lipid bilayers plus nuclear lamina

Question 13

chromatin=

Answer 13

DNA associated with protein

- within a chromosome

Question 14

why package DNA?

Answer 14

organize it and protect it from damage

Question 15

what are the 4 orders of DNA packaging?

Answer 15

1. nucleosome
2. solenoid/ 30nm fiber
3. looped domains
4. mitotic chromosome

Question 16

describe the 1st order of packaging

Answer 16

nucleosome:

- DNA wrapped around a histone octamer

Question 17

describe the 2nd order of packaging

Answer 17

solenoid/ 30nm fiber

- nucleosomes stack with the help of histone H1

Question 18

describe the 3rd order of packaging

Answer 18

looped domains

• 30nm fiber loops off a non-histone protein scaffold
• found in all cell stages

Question 19

describe the 4th order of packaging

Answer 19

mitotic chromosome

• fully condensed chromosome only appears during cell division
• so tightly wound that you can’t get any info/ gene expression off it

Question 20

histone =

Answer 20

pos charged proteins

Question 21

the rough ER is covered in ___ which are the enzymes of____

Answer 21

ribosomes

translation

Question 22

The ____ ___ is associated with translation of proteins destined for within the endomembrane system. They’re called ___ ribosomes (___ribosomes are free floating in cytoplasm)

Answer 22

rough ER
bound
free

Question 23

function of rough ER?

Answer 23

• site of protein quality control (lots of chaperones, folding)
• site of protein synthesis for proteins that fxn within the endomembrane system

Question 24

Proteins destined for the cytoplasm or nucleoplasm are synthesized on ____ ribosomes

Answer 24

free

Question 25

proteins destined for the plasma membrane or are exported/ secreted are synthesized on ___ ribosomes

Answer 25

bound

Question 26

the smooth ER has no ___

Answer 26

ribosomes

Question 27

List 4 examples of functions of the smooth ER

Answer 27

- ion storage (Ca2+) - phospholipid synthesis - steroid synthesis - detoxification of drugs and alcohol

Question 28

The _____ _____ receives cargo from the ER (everything the ER makes) and sorts cargo to 3 different destinations: 1. 2. 3.

Answer 28

Golgi apparatus 1. lysosome 2. plasma membrane 3. back to ER

Question 29

The golgi packages cargo into ___ | it's like the FedEx of the cell

Answer 29

vesicles

Question 30

The structure of the golgi is a set of flattened membranous sacs called ____

Answer 30

cisternae

Question 31

2 models of golgi trafficking

Answer 31

1. Vesicle Trafficking: - cargo from ER moves through CIS, medial, and trans (vesicle containing cargo comes out of the shipping side- trans) 2. Cisternal Maturation - cargo from ER enters CIS and stays there; the CIS moves, not the cargo (escalator analogy) - New CIS cisternae forms by fusion of vesicles from ER - trans golgi turns into vesicles

Question 32

Evidence for Vesicle trafficking model (Golgi)

Answer 32

- small vesicles are associated w/ golgi | - there are cisternal- specific enzymes

Question 33

Evidence for Cisternal Maturation model (Golgi)

Answer 33

- molecules too big to fit in the golgi- associated vesicles can move through golgi

Question 34

lysosomes can ___ anything

Answer 34

digest

Question 35

____ contain many hydrolytic enzymes that fxn best @pH=5

Answer 35

lysosomes

Question 36

How to lysosomes maintain low pH? Why is it important to maintain low ph?

Answer 36

- they actively pump in H+ | - low pH protects the cells from accidental autophagy (eating itself)

Question 37

example of lysosomal storage disorder?

Answer 37

Tay Sachs- lack an enzyme to digest a particular lipid | - therefore the lipid accumulated and causes neuronal death

Question 38

Vacuoles have different fxns depending on cell type. List 3

Answer 38

- food vacuoles - contractive vacuoles: pump excess water out of the cell - cenrtal vacuole: specific organelle of plants - fxns in storage and part of plant endomembrane system

Question 39

List 3 organelles not in the endomembrane system. | Why aren't they in the endomembrane system?

Answer 39

- mitochondria and chloroplasts - peroxisomes (involved in detox of alcohol, metabolism of fats- dangerous rxns happen here) - cytoskeleton (fxn in support, motility and cell shape) Because they have a different evolutionary origin

Question 40

what are the 3 different fibers that make up the cytoskeleton?

Answer 40

- microtubules (MT) - microfilaments - intermediate filaments

Question 41

Microtubules are composed of ___ ___

Answer 41

tubulin dimers

Question 42

Function of microtubules:

Answer 42

compression resistance (rods prevent squish)

Question 43

tubulin (the monomer of microtubules) is a diamer of ___;___ tubulin monomers

Answer 43

alpha; beta

Question 44

motor protein=

Answer 44

protein that change shape with ATP hydrolysis that generates force

Question 45

2 motor proteins associated with microtubules

Answer 45

1. Kinesin: (+) end directed MT motor; uses monkeybar movement 2. Dynein: (-) end directed MT motor mechanism of dynein movement unclear * note: (-) end is on the left of the MT, (+) on right

Question 46

example of MT function

Answer 46

eukaryote flagellum | - movement is generated by dynein (kinesin moves vesicles)

Question 47

microfilaments (MF) or "actin filaments" are composed of ____ monomers and is a double twisted chain of ____ ____

Answer 47

actin | actin subunits

Question 48

fxn of microfilaments

Answer 48

tension resistance | - movement: cytokinesis and muscular contraction

Question 49

what's the 'motor' of microfilaments?

Answer 49

myosin | eg. in muscles, pulling of myosin shortens the muscle

Question 50

Intermediate filaments function in ____ ___ (like MFs)

Answer 50

tension bearing

Question 51

structure of intermediate filaments

Answer 51

many different subunit types that form rope-like filaments

Question 52

do intermediate filaments have any associated motor proteins?

Answer 52

no

Question 53

give 2 examples of intermediate filaments

Answer 53

- laminin (intermediate filament forming nuclear lamina) provides support - keratin- in hair and nails