3.1 Cellular compartments and protein sorting

Question 1

What does this organelle do?

Answer 1

• Fatty acid break down
• Phospholipid synthesis
• Pentose PO₄ pathway

Question 2

What does this organelle do?

Answer 2

• Breakdown of protein, nucleic acids, cell debris, carbohydrates, lipids
• Signalling
• membrane repair

Question 3

What is the organelle lumen equivalent to?

Answer 3

Organelle lumen is equivalent to the extracellular space

Question 4

How does the nucleus and mitochondria differ from its lumen being equivalent to the extracellular space?

Answer 4

Nucleus and mitochondria have two membranes

Question 5

What is the interior of the nucleus equivalent to?

Answer 5

• Nuclear envelope is a double membrane
• Interior of nucleus is equivalent to and continuous with the cytosol

Question 6

How does the evolution of the nucleus explain why the interior of the nucleus and cytosol are equivalent?

Answer 6

• DNA in the cytosol of the prokaryotic cell had the membrane infold and circle around it
• As part of invagination the ER was formed
• While the nucleus matrix and cytosol are topologically equivalent - there is still a gate that allows only certain molecules to pass between the 2 compartments

Question 7

How did mitochondria and chloroplasts evolve?

Answer 7

• By the engulfment of prokaryotic cell, Endosymbiosis theory
• Two membranes, one from invagiation and one its original membrane
• To get into mitochondria, proteins must pass ONE or TWO membranes and an intermembrane space

Question 8

Which organelles are topologically equivalent?

Answer 8

Question 9

WHich proteins play a key role in the ER?

Answer 9

Question 10

Where do proteins begin synthesis?

Answer 10

All proteins begin synthesis on free ribosoems in the cytosol

Question 11

What are the challenges of protein traffic in the cell?

Answer 11

• Getting from cytosol into various compartments - access (topology)
• Getting to the right compartment (targeting)

Question 12

What are the three mechanisms for getting across the compartments in a cell?

Answer 12

Question 13

What is gated transport?

Answer 13

Movement between the cytosol and the nucleus (topologically equivalent)

Question 14

What is transmembrane transport as a mechanism for getting access to compartments?

Answer 14

• Movement to lumen of mitochondria, plastids, peroxisomes and ER (not topologically equivalent)
• Protein translocators

Question 15

What is vesicular transport as a mechanism for getting access to compartments?

Answer 15

• Movement between ER and other organells plus cell surface (topologically equivalent)
• Getting to the right compartment (targetting)