lecture 2 - part I - NUCLEUS

Question 1

what is a nucleus?

Answer 1

The nucleus is the most prominent membrane bounded organelle. It is found in eukaryotes and it contains linear DNA molecules. Moreover it is the controlling center of the cell. Just very few cells do not have a nucleus, for example RBC, which is red blood cell. Some cells have multiple nuclei.

Question 2

write the different structures of the nucleus

Answer 2

nuclear envelope
nuclear pore complex
nuclear lamina
nucleoplasm

Question 3

the nuclear envelope is:

Answer 3

highly regulated - not all substances can pass through it; some things can enter, some things can not
double layered - there is an outer (external) and an inner (internal) layer of the nuclear envelope
complex - it is complex because it has so many different structures attached to it; like carbohydrates, proteins, fats or a combination of them

Question 4

the nuclear pore complex

Answer 4

the nuclear pore complex
is a protein complex, a structure mainly made up of proteins
it forms a channel for different things to pass through it or enter and exit the nucleus
the proteins of NPC are called nucleoporins (Nups)

responsible for the protected exhange of components = this means that things inside the nucleus and outside or in the cytoplams enter and exit the nucleus through the NPC; this entrance and exit is the exchange and this must be protected by the NPC
density = how compact or how many NPCs there are = depends on the cells’ functions = 30-50 pores per 1 mm sqd

Question 5

The nuclear lamina is involved in most nuclear activities:

Answer 5

DNA replication, transcription, nuclear and chromatin organization, cell cycle regulation, cell development and differentiation, nuclear migration, apoptosis.

Question 6

five major classes of histones

Answer 6

H1, H2A, H2B, H3, H4

Question 7

Histones contribute to…

Answer 7

histones contribute to packing of DNA

Question 8

Histones can be changed by enzymes

Answer 8

Histones can be changed by enzymes

Question 9

Positively charged amino acids of histones will form ionic bounds with negatively charged DNA

Answer 9

Positively charged amino acids of histones will form ionic bounds with negatively charged DNA

Question 10

Histones are called to be acetylated if an acetyl group is added to histones by enzymes

Answer 10

Histones are called to be acetylated if an acetyl group is added to histones by enzymes

Question 11

Histones are called to be methylated if a methyl group is added to histones by enzymes

Answer 11

Histones are called to be methylated if a methyl group is added to histones by enzymes

Question 12

what is non-histones

Answer 12

they are small acidic proteins

Question 13

examples of non-histones

Answer 13

phosphoproteins, enzymes, for example DNA polymerase and RNA polymerase

Question 14

nucleoproteins

Answer 14

are the proteins that are found in or associated with the nucleus

Question 15

what is nucleoprotein made up?

Answer 15

proteins and nucleic acids

Question 16

proteins can be of two types

Answer 16

histones and non-histones

Question 17

nucleic acids are of two types

Answer 17

DNA and RNA

Question 18

what is nucleoplasm and karyoplasm

Answer 18

the protoplasm of the nucleus of a cell is called nucleoplasm (karyoplasm)

Question 19

nucleoplasm/karyoplasm

Answer 19

is the fluid or gel-like substance of the nucleus with suspended chromatin material, nucleolus, and other particulate elements (such as proteins and nucleic acids), of the nucleus.

Question 20

the major component of nucleoplasm are

Answer 20

nucleoproteins

Question 21

lamina consist of proteins

Answer 21

nuclear lamins