lectures 5-6

Question 1

properties of nuclear envelope

Answer 1

double membraned
interacts with endoplasmic reticulum
contains nuclear pores

Question 2

euchromatin

Answer 2

transcriptionally active
mRNA made by RNA polymerase II
‘lighter’ areas

Question 3

heterochromatin

Answer 3

remains packed after mitosis - more condensed

transcriptionally inactive - no mRNA made

Question 4

nuclear lamina

Answer 4

• net of fibres
• prevent clustering of nuclear pores
• disassembles/falls apart with the nuclear envelope during mitosis by phosphorylation of the lamins by kinases (lamins form intermediate filaments)
• only found in animal cells
• provide mechanical support and stability

Question 5

nuclear pores

Answer 5

• 8-fold symmetry – 8-subunit protein complex
• highly organised and equally distributed
• control nuclear transport – act as a gate and restrict transport of large proteins
• 30 different nucleoporins in a pore form the selective gates

Question 6

nucleolus

Answer 6

• assembles ribosomal subunits from proteins and exports them to cytoplasm
• fibrillar components – rRNA transcription
• granular components – ribosome assembly site

Question 7

what are the compartments of the endomembrane system

Answer 7

Nucleus - Endoplasmic Reticulum - Golgi Apparatus - Lysosome/Vacuole - Endosomal compartment - Transport vesicles - Peroxisomes

Question 8

what are the 3 vesicular trafficking pathways

Answer 8

1. secretory
2. endocytic
3. retrieval-recycling

Question 9

what ‘cargo’ do transport vesicles carry

Answer 9

integral proteins
phospholipids
cholesterol

Question 10

how are transport vesicles moved

Answer 10

molecular motors

Question 11

endoplasmic reticulum

Answer 11

• consists of membranous sacs and branched tubules
• Proteins can diffuse and migrate within the motile tubules
• extension of nuclear envelope

Question 12

differences between SER and RER

Answer 12

smooth:
-	calcium storage for cell signalling
-	lipid synthesis
-	detoxification of drugs/poisons
-	metabolism of carbohydrates
rough:
-	processing of secretory proteins

Question 13

golgi apparatus

Answer 13

Disc-shaped stack of membranes
Each golgi receives information at the Cis site from ER and processes it in golgi network
Sends information to plasma membrane or lysosomes from Trans site by vesicles
Some vesicles are sent back to ER by maturation of the golgi cisterna – retrieval-recycling pathway
Double membranes fold around forming compartments
involved in membrane trafficking

Question 14

functions of oligosaccharide

Answer 14

1. provide protection against pathogens (e.g. mucus coat on epithelia)
2. serves in cell-cell recognition and signalling
3. marks progression of the protein
4. helps folding and interaction with other proteins

Question 15

where are oligosaccharide chains processed

Answer 15

golgi cisterna

Question 16

how are oligosaccharides linked to proteins

Answer 16

1. glycosylated - sugar attached

2. linked to asparagine by N or O

Question 17

what are the 3 types of endosome involved in processing

Answer 17

• Early endosome
• Recycling endosome
• Late endosomes

Question 18

membrane trafficking along endocytic pathway

Answer 18

vesicle formed at plasma membrane
fusion of vesicle with early endosome
EITHER:
1. recycling of early endosome
2. degradation/maturation to late endosome and that goes to golgi and matures to lysosome