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Eukaryotic Cell Biology > The Nucleus > Flashcards

The Nucleus Flashcards

1
Q

How much of the cell’s cytoplasm is, roughly, occupied by the nucleus?

A

10%

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2
Q

What is the range of sizes that a nucleus can be?

A

2-10μm

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3
Q

What is the average size of the nucleus?

A

6μm

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4
Q

How would you describe the relationship between the volume of the cytoplasm and the size of the nucleus?

A

A linear relationship

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5
Q

When was the nucleus first discovered by Antonie Van Leeuwenhoek?

A

1719

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6
Q

In 1804, when drawing the nuclei of orchid cells, who first described the nucleus?

A

Franz Bauer

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7
Q

When was the nucleus described by Jan Purkyne as ‘vesicular germanitiva’ when studying chicken oocytes?

A

1825

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8
Q

When was the nucleus given it’s name by Robin Brown?

A

1831

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9
Q

The initial function of the nucleus was proposed in 1838. It was originally suggested to be involved in cell synthesis. What was it initially called?

A

A cytoblast

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10
Q

Between 1877 and 1884, scientists studied the nuclei of plant and animal cells. What did they believe the nucleus to be involved in?

A

Inheritance

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11
Q

When was the function of the nucleus finalised, thanks to the discovery of Mendelian genetics & the chromosome theory of heredity?

A

The 20th century

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12
Q

What is the shape of the nuclei in most cells?

A

Spherical

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13
Q

What type of cell has multi-lobed nuclei?

A

Neutrophils

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14
Q

What type of cells are multi-nucleated?

A

Skeletal muscle cells

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15
Q

What type of cells are binucleate?

A

Liver (hepatocyte) cells

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16
Q

What is the function of the nucleolus?

A

The site of ribosome synthesis

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17
Q

What is the function of the nucleoplasm?

A

The viscous, jelly-like part of the nucleus that holds all of the parts

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18
Q

What is the function of chromatin?

A

Areas of condensed DNA that hold genetic information

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19
Q

What is the function of the chromosomes?

A

Extremely condensed DNA that is ready for cell division

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20
Q

What is the function of the nuclear envelope?

A

It is the membrane barrier between the nucleus and the cytoplasm

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21
Q

What is the function of the nuclear pore complex?

A

It is a protein complex that allows import/export of material

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22
Q

How many membranes does the nuclear envelope have?

A

Two

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23
Q

What is the space between the two membranes of the nuclear envelope called?

A

The perinuclear space

24
Q

The inner membrane of the nuclear envelope has a protein lining. What is this called?

A

The nuclear lamina

25
Q

What does the outer membrane of the nuclear envelope connect to?

A

The rough Endoplasmic Reticulum

26
Q

What are the functions of the nuclear lamina (there are four)?

A
  1. To provide mechanical support and maintain nucleus shape.
  2. To regulate DNA replication and cell division.
  3. To organise chromatin.
  4. To anchor and stabilise the pores in the nuclear envelope
27
Q

How many different types of protein make up the nuclear pore complex?

A

30

28
Q

How many proteins in total make up the nuclear pore complex?

A

500

29
Q

What is the function of the cytosolic filaments of the NPC??

A

To provide stability, interact with cargo proteins and protect cells from external forces

30
Q

What is the function of the cytosolic and nuclear ring of the NPC?

A

They contain scaffold nuclear porins to stabilise the complex

31
Q

What is the function of the nuclear basket of the NPC?

A

To aid gene tethering and maintain membrane curvature

32
Q

Do products required for translation enter or exit the nucleus through the NPC?

A

Exit

33
Q

Do products required for transcription enter or exit the nucleus through the NPC?

A

Enter

34
Q

What is the width of a DNA double helix?

A

2nm

35
Q

What type of proteins does the DNA wrap itself around in nucleosomes?

A

Histone proteins

36
Q

What is the width of a chromosome?

A

1400nm

37
Q

What is a nucleosome?

A

A ‘beads on string’ structure that consists of DNA wrapped tightly around histone proteins

38
Q

How many nucleoli can a nucleus contain?

A

Any number between 1-4

39
Q

What three components make up the nucleolus?

A

Chromatin, fibrils, and granules

40
Q

What are fibrils in the nucleolus?

A

Parts of the DNA that is actively being transcribed into rRNA

41
Q

What are granules in the nucleolus?

A

rRNA molecules being packaged with cytoplasmic proteins

42
Q

What are the four functions of the nucleus?

A
  1. Compartmentalisation
  2. Pre-mRNA processing
  3. Gene expression
  4. Nuclear transport
43
Q

What is the purpose of pre-mRNA processing?

A

This allows introns within mRNA to be removed before translation, so that functional proteins can be synthesised

44
Q

What is splicing?

A

The removal of introns from mRNA

45
Q

What is passive nuclear transport?

A

Free diffusion of small molecules through the NPC, such as proteins and ions

46
Q

What is active nuclear transport?

A

The selective movement of larger proteins or RNA through the NPC. Requires energy and helper molecules

47
Q

What are the two helper molecules in active nuclear transport?

A

Importins and exportins

48
Q

How many histone proteins are transported through each NPC each minute?

A

100

49
Q

Proteins destined for the nucleus contain a specific amino acid sequence known as?

A

Nuclear localisation signal (NLS)

50
Q

Proteins destined for the cytoplasm contain a specific amino acid sequence known as?

A

Nuclear export signal (NES)

51
Q

In the nucleus, there is a high concentration of Ran-GTP due to the presence of what protein?

A

Ran-GEF

52
Q

In the cytoplasm, there is a high concentration of Ran-GDP due to the presence of what protein?

A

Ran-GAP

53
Q

What protein is responsible for exchanging GDP to GTP on the Ran protein found within the nucleus?

A

Ran-GEF

54
Q

Ran-GDP is brought back to the nucleus to be recycled by what protein?

A

NTF2

55
Q

In the cytoplasm, what protein hydrolyses Ran-GTP into GDP + Pi to trigger the dissociation of all components?

A

Ran-GAP

Eukaryotic Cell Biology (15 decks)

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