lecture 3-4 nuclear envelope

Question 1

eukaryotic ribosomes consist of 2 sections …

Answer 1

Large subunit and small subunit

Question 2

Function of ribosomes

Answer 2

a. Make proteins

b. Either free in the cytosol or attached to membranes

Question 3

Function of Nuclear envelope

Answer 3

The nuclear envelope (NE) is a highly regulated membrane barrier that separates the nucleus from the cytoplasm in eukaryotic cells. It contains a large number of different proteins that have been implicated in chromatin organization and gene regulation.

Question 4

b. Continuous plasma membrane (long board walk, no gap)

i. Why the double membrane: to protect DNA

Answer 4

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Question 5

c. Ribosomes stuck to surface: generate protein, protein will leave and will go into nuclear membrane: efficiency
i. One chromosome = one piece of DNA in its shape
ii. No relationship between chromosome number and species complexity

Answer 5

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Question 6

d. Chromatin

i. Chromatin is a substance within a chromosome consisting of DNA and protei

Answer 6

hhj

Question 7

e. Nuclear pore complex:

Answer 7

i. Job of npc. Let certain molecules in but be more selective, around 4000 of them on the surface
ii. Largest protein complex in the cell: exchanges molecules between nucleus and cytoplasm, prevents trasncport of molecules not supposed to cross the nuclear membrane
iii. Nuclear pore: path for assisted exchange of large molecules with the cytoplasm, small molecules pass through unassisted
iv. Why 4000? Turn style in a sports arena, funnel so you can view the crowd (aka moelcule0 only ones with tickets can get in (must have special protein that reacts with reactor to get in)
v. Protein complexes can direct molecules to certain areas
vi. Basket-like area: things generated on the inside can get out (protein involved with letting molecules in, is the same that tells which molecules they can leave)

Question 8

f. Space inside nucleus: filled with chromatin: combo of DNA and proteins

Answer 8

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Question 9

g. Condensed region of DNA:

Answer 9

i. RE: birthplace of ribosomes (ribosome part ran molecule)
ii. Ribosome forms one complex in nucleus, exits into RE, forms the next and then enters the cytoplasm
iii. Each DNA molecule with its associated proteins = eukaryotic chromosome

Question 10

h. Chromatin vs chromosome

Answer 10

i. Chromatin: collection of eukaryotic DNA molecules and associated proteins
ii. Chromosome: complete DNA with associated proteins

Question 11

ribosomes

Answer 11

a. Make proteins

b. Either free in the cytosol or attached to membranes

Question 12

ribosomes:

Answer 12

c. Bacteria and Archaea also have ribosomes, but different structure All life uses ribosomes, evidence of common ancestor

Question 13

d. Contain a large subunit and a small subunit

Answer 13

i. Comprised of RNA and protein
ii. Large subunit: involved in synthesis of proteins
iii. Small subunit: involved in coding of RNA
iv. Once in nuclear envelop, mature, and come out, could stay in cytosol and make proteins or enter the nuclear membrane
v. Proteins made on free ribosomes may remain in the cytosol, pass into the nucleus, or become parts of mitochondria, chloroplasts, cytoskeleton, or other cytoplasmic structures Proteins made on ribosomes attached to the endoplasmic reticulum (ER) follow a special path to other organelles in the cell
vi. Some ribosomes are attached to membranes others nuclear envelope, most: ER