Lecture 7 Cellular Organelles

Question 1

Prokaryote do not have a true ____

Answer 1

-nucleus

Question 2

Nucleoid =

Answer 2

region of condensed DNA

Question 3

Exocytosis/endocytosis occurs in _______ but not in prokaryotes

Answer 3

• eukaryotes

Question 4

Mitosis and meiosis in ______

Answer 4

• Eukaryotes

Question 5

Binary fission in ________

Answer 5

• prokaryotes

Question 6

Surface Area/Volume ratio

• *Need adequate surface area for nutrient/waste exchange
• > As cells get larger, the surface area to volume ratio ________

Answer 6

• decreases

Therefore, nutrient/waste exchange becomes more problematic due to insufficient surface area for a large volume cell

Question 7

Diffusion within the cell becomes problematic as the volume becomes _____

Answer 7

• Larger

Question 8

Potential for inadequate concentrations of _____ and ______

Answer 8

• reactants and catalysts

Question 9

How do some large cells overcome these limitations? An example would be muscle fibers…

Answer 9

• Each fiber has hundreds of nuclei (myonuclei) to support synthesis of RNA and proteins

Each fiber not really an individual cell – syncitium
Syncitium = large cell formed via the fusion of many smaller cells (myoblasts)

Question 10

In order for a fiber to grow (hypertrophy), it must add additional ______

Answer 10

• Myonuclei

Question 11

Where do myonuclei come from for hypertrophy of muscle cells?

Answer 11

• Additional myonuclei come from satellite cells that reside just outside of the muscle fiber
• The additional nuclei are required to support the increased level of RNA and protein synthesis

Question 12

The nucleus is surrounded by the ______ ________

Answer 12

• nuclear envelope

Question 13

Nucleoplasm =

Answer 13

=inside of the nucleus (except for the nucleolus)

Question 14

What are dissolved in the nucleoplasm (3)

Answer 14

Nucleotides, transcription factors, and enzymes

Question 15

Heterochromatin is _______ packaged

Answer 15

• Densely

Question 16

Constitutive heterochromatin is ______ condensed

Answer 16

-always

Question 17

Facultative heterochromatin is __ ___ condensed

Answer 17

• not always

Question 18

Euchromatin, as opposed to heterochrmation is packaged how?

- this allows for what?

Answer 18

• loosely packed

- > Allows for proteins to interact with the DNA- gene transcription

Question 19

Chromatin is a…..

Answer 19

• material that makes up a chromosome

Question 20

Muscle Fiber – myonucleus (the nuclei of a muscle fiber or cell)
…. have a very _____ level of ______, and is ______ in gene transcription

Answer 20

• High/ euchromatin

- Very active

Question 21

Muscle Satellite Cell – nucleus

• as opposed to a myonucleus, ___1__
  levels of ____2___, and higher levels of __3___

Answer 21

1. Low
2. euchromatin
3. heterochromatin

Question 22

Nuclear pores are….

Answer 22

• Large pores that allow for transport into and out of the nucleus through the nuclear envelope

Question 23

Nucleolus (nucleoli) is the site for

Answer 23

• rRNA and ribosomal protein synthesis

* Cells with high amounts of protein synthesis generally have large distinct nucleoli (neurons)

Question 24

Movement of proteins and rRNA through the nuclear pores is necessary for:

Answer 24

• ribosome assembly (protein synthesis)

- physiological signals to regulate gene expression

Question 25

4 main structural components of nuclear pore

Answer 25

1. Cytoplasmic Ring 2. Nuclear ring and basket - regulation 3. Lumenal rings – anchor (include anular ring) 4. Transporter (central granule) – involved in physical transport

Question 26

The function of the nuclear pore is to (2)

Answer 26

- mediate the energy dependent (GTP) transport of nuclear proteins, mRNA, and rRNA into and out of the nucleus - Allows passive diffusion of small molecules and ions, even some small proteins up to ~30,000 daltons

Question 27

Protein destined for the nucleus must have....

Answer 27

- nuclear localizing signal (NLS)

Question 28

NLS must be recognized by a ______ in order to get into the nucleus

Answer 28

- karyopherin In this case an importin

Question 29

Karyopherins are a...

Answer 29

....Class of proteins that assist in shuttling proteins across the nuclear envelope

Question 30

Protiens that assist in nuclear import =

Answer 30

- importins

Question 31

Proteins that assist in nuclear export =

Answer 31

- exportins

Question 32

Importins have both an _____ and _____ complex

Answer 32

alpha/beta (will usually function together)

Question 33

Importin ____ can sometimes function alone

Answer 33

- beta

Question 34

Importin α binds to the target protein at its _____ and to importin β. Thus, Importin α acts as an _____ protein between the cargo protein and importin β

Answer 34

- NLS (nuclear localization signal)/ adapter

Question 35

For nuclear export, there will be high ____ in the nucleus, and high _____ outside the nucleus

Answer 35

GEF, GAP

Question 36

Slide #27!!!!

Answer 36

Look at notes too

Question 37

mRNA rRNA are bound to protein to form _________ particles

Answer 37

- ribonucleoprotein (RNP) particles

Question 38

The proteins to be exported (including a protein in the RNP) must have a ____ ____ _____

Answer 38

-nuclear export signal (NES) The NES interacts with an exportin, which facilitates nuclear export

Question 39

In the nucleus the exportin: (4)

Answer 39

1. Bind with ran-GTP (ran-GTP is high in nucleus) 2. This allows it to bind its cargo (which must have a protein with an NES, except for tRNA) 3. Exportin then interacts with the NPC 4. And moves cargo out of nucleus

Question 40

Steps for cargo to exit the nucleus:

Answer 40

1. Exportin binds to Ran-GTP 2. Exportin-Ran-GTP binds to the cargo (at NES of Cargo) 3. Entire complex is exported via exportin interation with the nucleoporins of the NPC 3. In the cytosol, GTP is hydrolyzed and the Cargo and exportin are released 4. Exportin is then recycled back into the nucleus

Question 41

How does Ran get back into the nucleus?

Answer 41

1. In the cytosol, Ran-GDP associates with NTF2 (nuclear translocation factor 2) 2. Ran-GDP-NTF2 complex interacts with the NPC and translocates into the nucleus 3. The NTF2 releases Ran in the nucleus where Ran interacts with the GEF which binds a new GTP to Ran 4. Thus Ran-GTP levels are high in the nucleus providing the concentration gradient that helps to drive import and export

Question 42

NFAT is:

Answer 42

Transcription factor protein involved in many cellular processes... Along with calcineurin, NFAT transduces cellular signals (changes in Ca2+ concentration) into molecular signals (changes in gene expression) NFAT translocates into the nucleus upon dephosphorylation by calcineurin -Binds to DNA and alters transcription of specific genes

Question 43

The Nuclear lamina is:

Answer 43

Meshwork of fibrous proteins that line the inner surface of the nuclear envelope

Question 44

Nuclear lamina acts to (3)

Answer 44

- Form a supporting network of proteins that maintains the 3-D shape of the nucleus - Anchor and organize the chromatin - Act to transmit mechanical signals to the genes

Question 45

The Nucleolus is the site of ______ synthesis and ________ proteins

Answer 45

- rRNA/ ribosomal

Question 46

Core of nucleolus = Nucleolus Organizing Region (NOR), NOR is:

Answer 46

- segments of DNA with repeated sequences that code for rRNA and ribosomal protein

Question 47

Why does nucleolus appear dark

Answer 47

- Nucleolus appears dark due to a dense accumulation of rRNA and ribosomal protein

Question 48

Nucleolar fibrils=

Answer 48

- DNA and rRNA

Question 49

Nucleolar granules=

Answer 49

-ribosomal subunits