Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOL 201 > Topic 2: Organelles and the Nucleus > Flashcards

Topic 2: Organelles and the Nucleus Flashcards

1
Q

What is the function of eukaryotic organelles?

A

eukaryotic cells are composed of many different membrane bound compartments called organelles each of distinct functions

larger eukaryotic cells need a way of maintaining adequate concentrations of reactants (substrates) and catalysts (enzymes) for proper functioning of cellular activities

internal membranes allowed more space and seperation

specificity of function is achieved by differential localization of proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is compartmentalization?

A

organelles provide specificity of function and also concentration of reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the mitochondria?

A

double-membrane bound: one membrane is eukaryotic in origin, inner membrane is prokaryotic

contains own DNA: encodes some mitochondrial genes, most mitochondrial genes are nuclear encoded

mitochondrial genes are stored in the nucleus for protection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the endoplasmic reticulum?

A

a complex network of tubular membranes and flattened sacs (cisternae)

internal space of the ER is called the lumen

continuous with the other membrane of the nuclear envelope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is rough endoplasmic reticulum?

A

covered in ribosomes that sit on cytoplasmic face

bound ribosomes translate proteins destined for within endomembrane system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is smooth endoplasmic reticulum?

A

no association of ribosomes

involved in synthesis of lipids, detoxification, Ca++ storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the golgi body?

A

processing and packaging of proteins

site of secretory protein packaging and synthesis of polysaccharides

receives protein from the ER in vesicles (budded compartments)

once produced in the golgi, these proteins can then be passed along to other cellular compartments and including the plasma membrane

modifies cargo by glycosylation and other methods

ships cargo to other destinations within endomembrane system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are lysosomes?

A

digestive organelle of the cell

contains hydrolytic enzymes that digest only macromolecules (peptidase, DNAse, lipase, sucrase)

enzymes are highly specific to lysosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are ribsosomes?

A

protein synthesis

smallest organelle found in cells (30 nm in diameter)

composed of two subunits that differ in both size and shape

most numerous cell organelle

all translation begins in cytoplasm on free ribosomes (except the few mitochondrially translated proteins)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the plasma membrane?

A

semipermeable phospholipid bilayer

two membranes (or lipid bilayer) surrounds the cell and its organelles

defines the boundaries of the cell and retains its intracellular contents

consists of phospholipids, other lipids, proteins, and carbohydrates

each phospholipid consists of two hydrophobic tails (hydrocarbon) and a hydrophilic head (phosphate containing); amphipathic

phospholipids spontaneously form a bilayer due to: geometry (columnar shaped) and chemistry (amphipathic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is centrifugation?

A

when a particle is subject to centrifugal force, its rate of movement through a solution depends on the particles size and density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is sedimentation rate?

A

rate of movement through a solution, larger or denser particles have a higher sedimentation rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is subcellular fractionation?

A

using centrifugation to isolate and purify organelles and macromolecules based on their sedimentation rates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a centrifuge?

A

consists of a rotor that can be spun rapidly by a motor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How are sample prepared?

A

tissues/cells are first homogenized or disrupted to separate contents

sample forced through narrow orifice, ultrasonic vibration, osmotic shock, enzymatic treatment, manual grinding

important to keep organelles and macromolecules intact (often homogenization is performed in cold isotonic solutions)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is differential centrifugation?

A

supernatant is saved and spun again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is equilibrium or density gradient centrifugation?

A

add homogenate to a pre-established gradient, you get refined and pure fractions

18
Q

What are the different parts of the nucleus?

A
  1. Nucleoplasm: fluid of nucleus
  2. Nuclear Envelope: 2 lipid membranes, outer membrane is continuous with the ER
  3. Euchromatin: loosely packed DNA
  4. Heterochromatin: tightly packaged DNA
  5. Nucleolus: site of RNA transcription and ribosomal assembly
19
Q

What are nuclear pores (NPC)?

A

nuclear pores span the nuclear double membrane

composed of proteins called nucleoporins arranged in a very large complex

small ions, metabolites and small globular proteins can diffuse freely

other molecules must be actively imported/exported through nuclear pore

20
Q

What is the structure of the nuclear pores?

A

composed of 465 individual proteins

cytoplasmic side contains cytoplasmic filaments

pore complex spans both bilayer (octagonal pore)

transport is non-selective for anything smaller than 40 kDa

nuclear basket faces nucleoplasm

21
Q

What is nuclear import?

A

all proteins start translation in the cytoplasm therefore they must be imported into the nucleus

nuclear proteins such as: ribosomes, DNA polymerase, RNA polymerases, histones, etc. must all be imported into the nucleus by a specific mechanism

all nuclear-destined proteins contain a nuclear localization signal (NLS)

22
Q

How are proteins targeted in the nucleus?

A

the nucleus requires many proteins that are all synthesized in the cytoplasm to enter and exit in a regulated fashion

most of the molecules needed inside the nucleus are impermeable to the double membrane and must pass through nuclear pores

23
Q

How does a protein “know” it is supposed to go to the nucleus?

A

NLS = Lys-Lys-Lys or Arg-Lys-Lys/Arg

24
Q

What is the necessity experiment for NLS?

A

take it away and see if it still works

SV40T antigen = normally nuclear b/c has NLS

NLS was genetically deleted

reintroduced into cell culture

stained with immunofluorescence

protein was not nuclear localized

NLS is necessary for nuclear localization

25
Q

What is the sufficiency experiment for NLS?

A

pyruvate kinase is an enzyme that normally localizes to the cytoplasm

genetically engineered an NLS into a normally cytoplasmic protein

NLS-PK fusion protein localizes to nucleus

therefore NLS is sufficient for localization

26
Q

What is the mechanism of import into the nucleus?

A

cytoplasmic proteins called importins are responsible for recognizing and binding the NLS

importins are dimers of alpha and beta subunits forming a heterodimeric nuclear-import receptor

alpha subunit binds NLS, beta subunit binds NPC (cytoplasmic filaments of nuclear pore complex

entire nuclear import receptor: cargo (NLS containing protein) is moved across NPC into nucleus

inside nucleoplasm the NIR cargo complex interacts with Ran-GTP and allows dissociation

G proteins: a large class of small proteins that reversibly bind to GTP

27
Q

What are the steps of import into the nucleus?

A
  1. NLS containing protein = fully folded, translated
  2. NIR (receptor) binds NLS protein
  3. Translocation into nucleus (localization of Ran-GEF in nucleus allows formation of Ran GTP)
  4. Cargo Dissociation (Ran GTP binds NIR and causes release of cargo into nucleus)
  5. NIR and Ran GTP leave nucleus
  6. Ran GTPase activity in cytoplasm causes Ran GTP –> Rand GDP (Ran hydrolyzes it bound GTP, Ran GDP dissociates from receptor)
28
Q

What is nuclear export?

A

similar to import except now a group of exportins is used

proteins that shuttle in and out of the nucleus must have a Nuclear Export Signal (NES)

ribosomes would have both NLS and NES

29
Q

What are the steps of nuclear export?

A

exportin recognizes and binds NES

entire exportin-Ran-NES complex leaves through NPC

Ran GAP in cytoplasmic filaments hydrolyzes Ran GTP –> Ran GDP therefore causes exportin to release cargo

30
Q

What is the differences between import and export to the nucleus?

A

in export the Ran GTP is part of the cargo complex that is transported

31
Q

Why doesn’t import and export to the nucleus get mixed up?

A

same Ran protein

exportin and importin are differentially regulated by Ran
Ran GDP = in cytoplasm, Ran GTP = in nucleus

exportin works if bound to cargo AND Ran GTP
importin works if bound to cargo OR Ran GTP

32
Q

What is DNA packaging?

A

nuclear genetic material of eukaryotic exists in two states:
interphase chromosome: cell is not dividing, majority of the time
condensed chromosome: during cell division

33
Q

What is euchromatin?

A

loosely packaged DNA that is transcriptionally active, light staining regions

34
Q

What is heterochromatin?

A

tightly packages DNA that is inaccessible to transcription, dark staining regions

35
Q

What are nucleosomes?

A

1st order of chromatin packaging

a nucleosome consists of: histone octamer of H2A, H2B, H3, and H4

positive charge on histone interacts with the negative of the DNA backbone, therefore not sequence specific interactions

36
Q

What are histones?

A

highly conserved

histone H1 is less conserved but not part of core nucleosome

histone H3 has a tail of amino acids = site of regulation

histone tails can be reversibly phosphorylated, methylated or acetylated which changes degree of packaging methylation

methylation = closes chromatin = less transcriptionally active = heterochromatin

acetylation = opens chromatin = more transcriptionally active = euchromatin

37
Q

What is higher order packaging?

A

solenoid or 30 nm filament

coiling of nucleosome filament into higher-order, thicker filament

zig-zag ribbon structure that is wound into a helix

38
Q

What are non-histone scaffolding proteins?

A

the 30 nm fiber is then packaged further into looped domains by some DNA associating with non-histone scaffolding proteins

highly organized with regions of DNA associating together in a predictable way

39
Q

What are mitotic chromosomes?

A

fully condensed therefore transcriptionally active

40
Q

What is nuclease?

A

an enzyme that digests DNA by breaking phosphodiester bonds

2 types: exonuclease (pac-man), endonuclease (scissors)

endonuclease can only digest DNA in linker regions because the DNA is associated with histones

41
Q

What is an experiment with endonuclease?

A

uncoil DNA

expose to low concentrations of endonuclease )ensures random cuts)

run DNA on a DNA gel (separates DNA based on size)

low concentrations of endonuclease gives pattern of band sizes that represent multiples of nucleosome + linker length therefore linker is short

at higher concentrations only DNA protected in nucleosome is intact

BIOL 201 (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions