Final Exam

Question 1

Cytosol compartment function

Answer 1

contains many metabolic pathway; protein synthesis; the cytoskeleton

Question 2

Nucleus compartment function

Answer 2

contains main genome; DNA and RNA synthesis

Question 3

Endoplasmic Reticulum (ER) compartment function

Answer 3

synthesis of most lipids; synthesis of proteins for distribution to many organelles and to the plasma membrane

Question 4

Golgi Apparatus compartment function

Answer 4

modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another oganelle

Question 5

Lysosomes compartment function

Answer 5

intracellular degradation

Question 6

Endosomes compartment function

Answer 6

sorting of endocytosed material

Question 7

Mitochondria compartment function

Answer 7

ATP synthesis by oxidative phosphorylation

Question 8

Chloroplasts (in plant cells) compartment function

Answer 8

ATP synthesis and carbon fixation by photosynthesis

Question 9

Peroxisomes compartment function

Answer 9

oxidative breakdown of toxic molecules

Question 10

what is the fate of each protein after synthesis?

Answer 10

Protein Sorting

Question 11

Protein Sorting

Answer 11

Energy-dependent mechanisms for protein entry into an organelle from the cytosol

Question 12

Proteins are transported into organelles by three mechanisms

Answer 12

1. Transport through nuclear pores
2. Transport across membranes
3. Transport by vesicles

Question 13

What do Signal sequences do?

Answer 13

The signal sequence is a “flag” bound to an amino acid terminus and directs proteins to the correct compartment

Question 14

Signal sequences are ___________________ to direct a
protein to an organelle

Answer 14

necessary and sufficient

Question 15

Necessary (signal sequences)

Answer 15

removing a signal peptide from a protein that should go to the ER, the
protein remains in the cytosol (default location)

Question 16

Sufficient (Signal Sequences)

Answer 16

adding an ER signal peptide to a cytosolic protein, makes it move to
the ER

Question 17

Small molecules can freely diffuse through the nuclear pore but large
molecules like proteins cannot pass without _________________________

Answer 17

an appropriate sorting signal

Question 18

To pass through the nuclear pore
_________ need to present

Answer 18

proteins

Question 19

nuclear localization signal

Answer 19

(short stretch of lysines/arginines,
positive charges)

Question 20

nuclear transport receptors

Answer 20

recognize the nuclear transport
signal and help the protein
through by disrupting the gel-like
meshwork of nuclear fibrils

Question 21

Proteins remain in their fully
folded conformation (as they were in the ribosome)
throughout the _________ _________

Answer 21

transport process

Question 22

What drives nuclear transport?

Answer 22

Energy supplied by GTP hydrolysis

Question 23

Ran-GTP

Answer 23

high affinity for Nuclear Import Receptor; Nuclear

Question 24

Ran-GDP

Answer 24

low affinity for Nuclear Import Receptor; Cytoplasmic

Question 25

True or False: Proteins must be unfolded during transport.

Answer 25

true

Question 26

What helps re-fold the protein after transport

Answer 26

Chaperone Protiens

Question 27

What do N terminal signal sequences target?

Answer 27

proteins to specific site within the organelle

Question 28

What is the most extensive membrane in the cell that is also the entry point for proteins destined for several other organelles and the cell exterior?

Answer 28

The ER

Question 29

What kinds of proteins are transferred by the cytosol to the ER?

Answer 29

1. Soluble Protein 2. Transmembrane Protein

Question 30

Soluble Proteins

Answer 30

-Transferred completely to the ER lumen -Destined for secretion out of the cell or to the lumen of another organelle (not mitochondria or plastid)

Question 31

Transmembrane Proteins

Answer 31

-Partly translocated into ER, embedded in the membrane -Destined to reside in ER or the membrane of another organelle or plasma membrane

Question 32

What is happening while the proteins enter the ER?

Answer 32

While being synthesized

Question 33

What do the Membrane-bound ribosomes do?

Answer 33

make proteins that are translocated to the ER

Question 34

What makes all the other proteins?

Answer 34

Free ribosomes

Question 35

Steps of Signal Recognition in the cytosol

Answer 35

1. ER signal sequence on the growing polypeptide chain 2. Signal Recognition Particle (SRP) 3. SRP receptor in the ER membrane 4. Translocation channel