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Cellular Physiology > Lecture 7 Cellular Organelles > Flashcards

Lecture 7 Cellular Organelles Flashcards

1
Q

Prokaryote do not have a true ____

A

-nucleus

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2
Q

Nucleoid =

A

region of condensed DNA

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3
Q

Exocytosis/endocytosis occurs in _______ but not in prokaryotes

A
  • eukaryotes
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4
Q

Mitosis and meiosis in ______

A
  • Eukaryotes
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5
Q

Binary fission in ________

A
  • prokaryotes
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6
Q

Surface Area/Volume ratio

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

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

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7
Q

Diffusion within the cell becomes problematic as the volume becomes _____

A
  • Larger
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8
Q

Potential for inadequate concentrations of _____ and ______

A
  • reactants and catalysts
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9
Q

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

A
  • 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)

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10
Q

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

A
  • Myonuclei
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11
Q

Where do myonuclei come from for hypertrophy of muscle cells?

A
  • 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
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12
Q

The nucleus is surrounded by the ______ ________

A
  • nuclear envelope
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13
Q

Nucleoplasm =

A

=inside of the nucleus (except for the nucleolus)

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14
Q

What are dissolved in the nucleoplasm (3)

A

Nucleotides, transcription factors, and enzymes

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15
Q

Heterochromatin is _______ packaged

A
  • Densely
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16
Q

Constitutive heterochromatin is ______ condensed

A

-always

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17
Q

Facultative heterochromatin is __ ___ condensed

A
  • not always
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18
Q

Euchromatin, as opposed to heterochrmation is packaged how?

- this allows for what?

A
  • loosely packed

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

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19
Q

Chromatin is a…..

A
  • material that makes up a chromosome
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20
Q

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

A
  • High/ euchromatin

- Very active

21
Q

Muscle Satellite Cell – nucleus

  • as opposed to a myonucleus, ___1__
    levels of ____2___, and higher levels of __3___
A
  1. Low
  2. euchromatin
  3. heterochromatin
22
Q

Nuclear pores are….

A
  • Large pores that allow for transport into and out of the nucleus through the nuclear envelope
23
Q

Nucleolus (nucleoli) is the site for

A
  • rRNA and ribosomal protein synthesis

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

24
Q

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

A
  • ribosome assembly (protein synthesis)

- physiological signals to regulate gene expression

25
Q

4 main structural components of nuclear pore

A
  1. Cytoplasmic Ring
  2. Nuclear ring and basket - regulation
  3. Lumenal rings – anchor (include anular ring)
  4. Transporter (central granule) – involved in physical transport
26
Q

The function of the nuclear pore is to (2)

A
  • 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
27
Q

Protein destined for the nucleus must have….

A
  • nuclear localizing signal (NLS)
28
Q

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

A
  • karyopherin

In this case an importin

29
Q

Karyopherins are a…

A

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

30
Q

Protiens that assist in nuclear import =

A
  • importins
31
Q

Proteins that assist in nuclear export =

A
  • exportins
32
Q

Importins have both an _____ and _____ complex

A

alpha/beta (will usually function together)

33
Q

Importin ____ can sometimes function alone

A
  • beta
34
Q

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

A
  • NLS (nuclear localization signal)/ adapter
35
Q

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

A

GEF, GAP

36
Q

Slide #27!!!!

A

Look at notes too

37
Q

mRNA rRNA are bound to protein to form _________ particles

A
  • ribonucleoprotein (RNP) particles
38
Q

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

A

-nuclear export signal (NES)

The NES interacts with an exportin, which facilitates nuclear export

39
Q

In the nucleus the exportin: (4)

A
  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
40
Q

Steps for cargo to exit the nucleus:

A
  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
  4. In the cytosol, GTP is hydrolyzed and the Cargo and exportin are released
  5. Exportin is then recycled back into the nucleus
41
Q

How does Ran get back into the nucleus?

A
  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
42
Q

NFAT is:

A

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

43
Q

The Nuclear lamina is:

A

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

44
Q

Nuclear lamina acts to (3)

A
  • 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
45
Q

The Nucleolus is the site of ______ synthesis and ________ proteins

A
  • rRNA/ ribosomal
46
Q

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

A
  • segments of DNA with repeated sequences that code for rRNA and ribosomal protein
47
Q

Why does nucleolus appear dark

A
  • Nucleolus appears dark due to a dense accumulation of rRNA and ribosomal protein
48
Q

Nucleolar fibrils=

A
  • DNA and rRNA
49
Q

Nucleolar granules=

A

-ribosomal subunits

Cellular Physiology (3 decks)

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