Lec. 8: Nucleus, Ribosomes, Endomembrane System

Question 1

Chromatin

Answer 1

DNA and associated proteins responsible for synthesis of mRNA

Question 2

Nucleolus

Answer 2

An area inside the nucleus responsible for the Formation of ribosomal subunits

Question 3

Structure of the nucleus

Answer 3

• Enclosed by a double membrane (Inner and outer membrane
• Nuclear pores mediate transport in and out of nucleus

Substances that travel thru pores have tags called nuclear localization signals allowing them to pass thru pore complexes

Question 4

Ribosome

Structure, function

Answer 4

• synthesize proteins
• composed of rRNA with cytosolic proteins
• 2 subunits, large and small
• free ribosomes synthesize cytosolic proteins
• bound ribosomes to the rough ER synthesize integral membrane proteins and secreted proteins out of the cell

Question 5

Endoplasmic reticulum

Answer 5

• Continuous with nuclear envelope
• Membranous tubules
• Cisternae= internal membrane stacks with lumen
• Smooth ER=no ribosomes, Rough ER=ribosomes attached to outer membrane of nucleus

Question 6

Smooth ER function

Answer 6

Smooth:
- rich in enzymes
- synthesis of lipids (ovary and testis) synthesis of steroid hormones
- metabolism of carbohydrates, drugs, poisons- liver breakdown of glycogen or toxins (detox)
- calcium removal in muscle and secretory

Question 7

Rough ER function

Answer 7

Rough: ribosome bound
- processing of proteins by ER bound ribosomes
- Secretory proteins
- Membrane proteins

Question 8

Golgi apparatus

Answer 8

Finishes, sorts, ships
- flattened membranous sacs
- cisternae is the inernal space
- cis face=recieves
- trans face=ships

Question 9

How does transport occur in the Golgi?

Answer 9

INTO GOLGI
- ER produced vesicles fuse with cis face
- Transit cis to trans via vesicles (cisterna contains specific enzymes)
- Modifies proteins and phospholipds
- manufacturing of polysaccharides
OUT OF GOLGI
- vesicle is formed from trans face
- targeting tags in the vesicles membrane
- move along micotubules to specific locations

Question 10

Lysosome

What are some of its functions

Answer 10

Digestive organelle
- lysosomal enzymes and membrane made in rER and activated in Golgi
- Lysosomes fuse and digest vacuoles and damaged organelles (autophagy)
- Works best at low PH to hydrolyze and break down molecules

Digest food particles, recycling cellular organelles, destroy bacteria

Question 11

Lysosomal storage disorders

Answer 11

results from lack of specific enzymes that break down lipids or carbohydrates (ie fats and sugars) in lysosomes
- if a person lacks these enzymes=body cannot break down molecules for recycling and accumulate in lysosomes
- LSD is an autosomal recessive disorder

Tay Sachs Disease is an LSD