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Module 2 Notes 2023-24 CA$12.23   Add to cart

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Module 2 Notes 2023-24

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Enriched module 2 notes.

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  • October 26, 2023
  • 24
  • 2023/2024
  • Class notes
  • Dr. chris ward
  • All classes
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cassandranono
Section 1: Nucleus and DNA packaging

The Nucleus:

➔ Functions:

◆ Protect cell’s DNA

● Double layered membrane (nuclear envelope)

● Very selective nuclear pores

● Unique fluid called the nucleoplasm

◆ Allows DNA to be replicated and transcribed to mRNA when needed

◆ Regulates which molecules can access the DNA and separates the DNA from

other cell components

◆ Keeps all DNA organized since DNA is fragile

,DNA packaging:

➔ Cells are only microns in size, it has to carefully package DNA




Level 2: DNA is wrapped twice around proteins called histones to create nucleosomes (shortens DNA 7 fold)

(200bp of DNA are wrapped around one octamer (core DNA))

Level 3: String of nucleosomes coiled in a spiralling chromatin fibre (shortens DNA by 42 fold)

Level 4: chromatin fibres formed into chromatin looped domains (shortens DNA by 750 fold)

Level 5: chromatin looped domain further compressed and folded into heterochromatin of 700nm - highly

condensed DNA - further condensed into chromosomes during cell division

Level 1-4 = Euchromatin - active DNA - replication of chromosomes, reading a strand of DNA to make

mRNA)

, Section 2: The endomembrane system

The linked machinery that processes transporting cargo throughout the cell

➔ The nucleus is connected to the ER cisternae by the outer layer nuclear envelope -

nuclear pores connect ER and nucleus so molecules can freely pass through

➔ Vesicle transport - vesicles used to shuttle material between organelles

◆ Small vesicles bud off of the lipid membrane of organelles or the cell, with the

purpose of transporting e.g soluble or membrane-bound proteins

◆ Once reaching their final destination, they fuse with other lipid membranes

➔ Golgi network




◆ Trans Golgi addition:

● Each cell has different requirements for their trans Golgi network

(different cell type, different proteins needed)

● Retrograde transport: Some proteins have an ER retention signal so the

trans Golgi network packs them with COPI coating proteins so they are

recycled back to the ER

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