Cell Bio Quiz set 4: Chap 16 and 18

Signal sequences that direct proteins to the correct compartment are _________. A) added to proteins through post-translational modification B) added to a protein by a protein translocator. C) encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination. D) always removed once a protein is at the correct destination

C) encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination. Signal sequences are found within the amino acid sequence of proteins. They are sometimes removed when the protein is at the correct destination [choice (d)], but not all are removed. For example, nuclear import signals are not removed once a protein is inside the nucleus. A protein translocator resides in the membrane and helps transport soluble proteins across the membrane [choice (b)], but does not add signal sequences to proteins.

Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels? A) lysosome -> endosome -> plasma membrane B) ER -> lysosome -> plasma membrane C) Golgi -> lysosome -> plasma membrane D) ER -> Golgi -> plasma membrane

D) ER --> Golgi --> plasma membrane

Which of the following statements about nuclear transport is true? A) mRNAs and proteins transit the nucleus through different types of nuclear pores. B) Nuclear import receptors bind to proteins in the cytosol and bring the proteins to the nuclear pores, where the proteins are released from the receptors into the pores for transit into the nucleus. C) Nuclear pores have water-filled passages that small, water-soluble molecules can pass through in a nonselective fashion. D) Nuclear pores are made up of many copies of a single protein.

Nuclear pores have water-filled passages that small, water-soluble molecules can pass through in a nonselective fashion. mRNAs and proteins can move through the same nuclear pore [choice (a)]. Nuclear import receptors bind to proteins in the cytosol and transit with them across the nuclear pore into the nucleus [choice (b)]. Nuclear pores are made up of many copies of multiple proteins [choice (d)].

Proteins that are fully translated in the cytosol and lack a sorting signal will end up in ____. A) Cytosol B) the mitochondria C) the interior of the nucleus D) the nuclear membrane.

The Cytosol Proteins produced in the cytosol that lack sorting signals remain in the cytosol. Proteins produced in the cytosol and destined for the mitochondria [choice (b)] or the interior of the nucleus [choice (c)] will have a sorting signal to direct the protein to its proper location. Proteins destined for the nuclear membrane [choice (d)] are not translated in the cytosol.

Testosterone functions inside a cell by _____.

binding with a receptor protein that enters the nucleus and activates specific genes

Receptors found in signal transduction A) are always found in the membranes B) are always found in the cytoplasm C) are always found in the nucleus D) can be found in either the membrane, cytoplasm, or nucleus

can be found in either the membrane, cytoplasm, or nucleus

Vesicles from the ER enter the Golgi at the ______.

cis golgi network

A G-protein receptor with GTP bound to it _____.

is in its active state

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

ligand-gated ion channel

In general, a signal transmitted via phosphorylation of a series of proteins _____.

results in a conformational change to each protein