Which of the following is NOT a membrane-enclosed organelle in plant or animal cells?

a. Peroxisome

b. Nucleus

c. Endosome

d. Chloroplast

e. All of the above are membrane enclosed organelles

E. All of the above are membrane enclosed organelles

It is thought that eukaryotic cells developed membrane-enclosed organelles due to their:

a. High plasma membrane surface area to cellular volume ratio

b. Low plasma membrane surface area to cellular volume ratio

c. Neither A nor B

B. Low plasma membrane surface area to cellular volume ratio

In the Ran-GTP/GDP nuclear transport system, which of the following statements is NOT true:

a. The nuclear localization signal is located on the cargo protein destined for the nucleus

b. Hydrolysis of GTP results in Ran-GDP dissociation from the nuclear transport receptor

c. Binding of Ran-GTP to the nuclear transport receptor occurs in the cytosol

d. Hydrolysis of GTP occurs in the cytosol

e. All of the above are true

C. Binding of Ran-GTP to the nuclear transport receptor occurs in the cytosol

Suppose attaching GFP to a protein of interest is a popular method to study the localization, either cytosolic or 

nuclear, of that protein within a cell (it is). What does this method assume?

a. The GFP sequence itself does not contain a nuclear localization signal

b. GFP alone is a small enough protein to diffuse freely through nuclear pores

c. GFP alone is a large enough protein to require active localization into the membrane

d. A and B

e. A and C

D. A & B

Start transfer sequences and stop transfer sequences are similar in that:

a. Both are hydrophobic

b. Both are hydrophilic

c. Both are cleaved by signal peptidase

d. A and C

e. B and C

A. Both are hydrophobic

In the process of translocating a polypeptide across the membrane of the endoplasmic reticulum, a stop transfer 

sequence halts the process. What eventually becomes of the stop transfer sequence?

a. It forms an α-helical membrane-spanning segment of the protein.

b. It forms a β-barrel membrane-spanning segment of the protein

c. It is cleaved from the protein.

d. It is translocated into the lumen of the endoplasmic reticulum.

A. It forms an α-helical membrane-spanning segment of the protein.

Proteins in the cytosol that are destined for other organelles must first enter the:

a. The nucleus

b. The endoplasmic reticulum 

c. The Golgi apparatus

d. The lysosomes

e. The plasma membrane

B. The endoplasmic reticulum

Clathrin is a protein that:

a. Coats vesicles budding from the golgi apparatus on the outward secretory pathway

b. Coats vesicles from the plasma membrane on the inward endocytic pathway

c. Both A and B

d. Neither A nor B

C. Both A & B

SNARE proteins are located on:

a. Transport vesicles

b. Target membranes

c. Both transport vesicles and target membranes

d. Neither transport vesicles nor target membranes

C. Both transport vesicles and target membranes

In the endoplasmic reticulum, individual sugars are added one by one to a protein to create an oligosaccharide 

side chain.

a. True

b. False – oligosaccharides are added as a whole via a specialized lipid

c. False – oligosaccharides are added as a whole via a specialized protein

B. False – oligosaccharides are added as a whole via a specialized lipid

Which type of protein binds to improperly folded or improperly assembled proteins in the ER, holding them there until proper folding occurs?

a. Tethering proteins

b. Glycosylating proteins

c. Antibody proteins

d. SNARE proteins

e. Chaperone proteins

E. Chaperone proteins

Which mechanism is used for degrading entire organelles of a cell, such as a defective mitochondrion?

a. Autophagy

b. Apoptosis

c. Phagocytosis

d. Endocytosis

e. Ubiquitination

A. Autophagy

Which of these forms of cell-cell communication typically travels the longest distance from the originating cell to 

the target cell?

a. Contact-dependent communication

b. Paracrine communication

c. Endocrine communication

d. Neuronal communication

C. Endocrine communication

Which of the following statements about steroid hormones is NOT correct?

a. Steroid hormones include cortisol, estradiol, testosterone, and thyroxine

b. The majority of steroid hormones pass through the plasma membrane due to their hydrophobic nature

c. Steroid hormones bind intracellular hormone receptors which directly regulate transcriptional gene 

activation and repression

d. Each hormone binds a different hormone receptor and, in turn, activates and represses a unique set of 

target genes

e. All of the above are correct

E. All of the above are correct

Nitric oxide (NO) acts only on neighboring cells (as a local mediator in paracrine signaling) because:

a. So little is produced by the signaling cell.

b. It is rapidly washed away by the blood stream.

c. It is rapidly converted to nitrates and nitrites in the target cell.

d. It is rapidly converted to nitrates and nitrites in the extracellular fluid.

D. It is rapidly converted to nitrates and nitrites in the extracellular fluid.

Which of the following is NOT one of the basic classes of cell-surface receptors?

a. Hormone receptors

b. G-protein-coupled receptors

c. Ion-channel-coupled receptors

d. Enzyme-coupled receptors

A. Hormone receptor

Which of the following statements about the inositol phospholipid signaling pathway is NOT true? 

a. The inositol phospholipid pathway is activated by GPCRs which activate the phospholipase C, a signaling molecule that also happens to be a phospholipid

b. Phospholipase C cleaves the sugar-phosphate head off inositol phospholipid to generate IP3 and diacylglycerol (DAG)

c. DAG remains embedded in the plasma membrane where it recruits protein kinase C (PKC)

d. IP3 is released into the cytosol where it binds to and opens Ca2+

channels in the ER membrane

e. Binding of DAG to PKC requires cytosolic Ca2+

f. All of the above are true

A. The inositol phospholipid pathway is activated by GPCRs which activate the phospholipase C, a signaling 

molecule that also happens to be a phospholipid

The concentration of free Ca2+

in the cytosol of an unstimulated cell is kept low compared with its concentration in both the extracellular fluid and the endoplasmic reticulum. Which of the following does not help maintain this difference? 

a. Membrane-bound Ca2+

pumps in the plasma membrane

b. Ca2+ destroying enzymes in the cytosol

c. Membrane-bound Ca 2+ pumps in the ER membrane

d. Ca2+ binding proteins in the cytosol

e. All of the above maintain the concentration difference

B. Ca2+ destroying enzymes in the cytosol

Adaptation in signaling pathways allow a cell to remain sensitive to signals despite:

a. Having mutant downstream adaptor proteins that may or may not bind the signaling receptor

b. The slow speed of signal propagation upon stimulation

c. The rapid speed of signal propagation upon stimulation

d. The absence of second messengers

e. Experiencing a wide range of background levels of stimulation

E. Experiencing a wide range of background levels of stimulation

Mutant Ras genes, which are found in approximately ____ of cancers, code for Ras proteins that are ______. 

a. 30%; constitutively active

b. 30%; constitutively inactive

c. 80%; constitutively active

d. 80%; constitutively inactive

e. 80%; misfolded

A. 30%; constitutively active