Biochem Exam 2 - protein sorting

Question 1

What are the major intracellular components of an animal cell?

Answer 1

• cytosol
• lysosome
• golgi appartur
• mitochondria
• endosome
• peroxisome
• nucleus
• plasma membrae
• ER with membrane bound polyribosomes
• free polyribosomes

Question 2

Can protein re-cross membrane to get back inside a cell?

Answer 2

Yes, proteins that have crossed a membrane are no longer topologically inside the cell. They must re-cross the membrane to get back inside the cell.

Question 3

How do vesicles move?

Answer 3

Vesicles move from compartment to compartment within a cell by budding off and membrane fusion

Question 4

Where do proteins have their signal sequences?

Answer 4

Many proteins have signal sequences at their amino terminus that direct the proteins to cross the membrane. Fewer proteins have internal signal sequences.

Question 5

Does the nucleus allow molecules to pass through?

Answer 5

The nucleus is surrounded by a double lipid membrane bilayer however nuclear pores allow molecules, including proteins to pass from the cytosol into the nucleus and back.

Question 6

How do larger proteins pass through the nucleus pore?

Answer 6

By active transport

Question 7

What do nucleus import receptors do?

Answer 7

They bind to nucleus transport signals found on some nucleus bound proteins and facilitate transport into the nucleus.

Question 8

Does it require signals to transport protein from cytosol into lumen of mitochondria?

Answer 8

yes, it generally requires multiple signals to transport proteins from the cytosol into the lumen of the mitochondria.

Question 9

How many protein translators are there in the mitochondrial membrane?

Answer 9

There are multiple protein translators in the mitochondrial membrane. Each translator interacts with a specific set of proteins.

Question 10

Does transporting of protein into the mitochondria require energy?

Answer 10

YAS

Question 11

How to proteins enter peroxisomes?

Answer 11

They do it using a mechanism similar to mitochondrial entry

Question 12

How do proteins travel from ER?

Answer 12

Proteins travel from the ER through the Golgi to many sites.

Question 13

What does a signal recognition protein (SRP) do?

Answer 13

It binds to the signal sequence during translation and directs the nascent (freshly generated) peptide to the ER membrane

Question 14

Is ATP required to transport protein through mitochondrial membrane?

Answer 14

Proteins bound for the mitochondria are translated in the cytosol and then transported through the mitochondrial membrane - and YEA this requires ATP

Question 15

Is energy required for proteins to head through the ER membrane?

Answer 15

Proteins that are headed into or through the ER are transported through the ER membrane during translation. so NO this doesn’t require any additional energy

Question 16

What does carbohydrate modification of proteins in ER do?

Answer 16

carbohydrate modification of proteins in the ER helps direct them to their ultimate location

Question 17

What is the default pathway?

Answer 17

if there are no other signals directing the proteins to other locations, this send the protein to the cell surface.

Question 18

What happens in regulated secretory pathway?

Answer 18

In regulated secretory pathway cells store proteins in secretory vesicles until they are signaled to release them from the cell by fusion of the vesicle with the cellular membrane.