Intracellular Processes

Question 1

Where are proteins produced

Answer 1

One free ribosomes or ribosomes attached to ER

Question 2

Difference between free ribosomes and those attached to ER

Answer 2

Nothing apart from what protein they are producingq

Question 3

How do human ribosomes differ from bacterial ones

Answer 3

Have two components,

Humans have 60S + 40S to give total size 80S

Bacteria have 50S + 30S to give total size 70S

Question 4

How do ribosomes know to go to ER

Answer 4

Protein being produced contains a signal peptide on N terminal

Signal peptide binds to Signal Recognition Particles, floating around cytoplasm, which take it to SRP receptor on ER

Question 5

Proteins made in the cytoplasm are sent where?

Answer 5

Nucleus

Mitochondria

Peroxisomes

Question 6

Proteins made on the ER are sent where and for what

Answer 6

Golgi apparatus for protein sorting

Question 7

Describe how the golgi apparatus sends proteins to their correct destination

Answer 7

Different vesicles containing proteins from the ER merge and form the cis cisterna of the GA

Cis certerna moves through the GA, and proteins undergo enzymatic modification which tells them where to go

Once it reaches the end, it becomes the trans cisterna before vesicles bud off to their destination

Question 8

The addition of what molecule prescribes a protein for the lysosome

Answer 8

Mannose-6-Phosphate

Question 9

The addition of what molecule prescribes a protein for exocytosis

Answer 9

Stop translocation protein

Question 10

Apart from protein delivery, what other function does the GA have

Answer 10

Post-translational modification of proteins eg. glycosylation

Question 11

Glyoproteins vs proteoglycans

Answer 11

Proteoglycans contain a much larger sugar component

Question 12

Name four other post-translational modifications and their function

Answer 12

Phosphorylation which alters protein activity

Acetylation which alters gene expression in histones

Ubiquitination which targets protein for degradation

Farnesylation which targets protein for membrane

Question 13

What are the two types of protein degradation

Answer 13

Lysosomal and proteasomal

Question 14

When is lysosomal degradation used

Answer 14

For proteins with a long half life >20 hours

Extracellular proteins

Pathogenic proteins in phagocytosis

Membrane proteins via endocytosis

Question 15

How does endosome become lysosome

Answer 15

Early endosome matures into late endosome and eventually lysosome

Question 16

What is autophagy

Answer 16

The process of a cell destroying old, faulty components to make new fresh ones

Question 17

Describe the structure of a proteasome

Answer 17

A tube with proteases on the outside

Protein stopper controlling entry/exit

Question 18

Is proteasomal degradation ATP dependant?

Answer 18

Yes

Question 19

When is proteasomal degredation used

Answer 19

Proteins with short half-life <20 hours

Key metabolic proteins and defective proteins

Proteins tagged with ubiquitin

Question 20

What tag sends a protein for proteasomal degradation

Answer 20

Ubiquitination