MCB 410 Exam 1 Lecture Questions

Compared to the normal situation in which actin monomers carry ATP what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments?

Actin filaments would grow longer.

Which of the following statements about gap junctions is FALSE?

Because gap junctions only allow uncharged molecules to pass through, they are not used for electrically coupling cells.

Which of the following statements about clathrin-coated vesicle budding is FALSE?

Clathrin molecules directly bind to and select cargoes for transport.

Given what you know about the differences between prokaryotic cells, and eukaryotic cells which of the following biological processes is suitable for study using E. coli as the model organism?

DNA replication

Which of the following statements about membrane-enclosed organelles is TRUE?

In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane.

Active transport requires the input of energy into a system to move solutes against their electrochemical and concentration gradients. Which of the following is NOT one of the common ways to perform active transport?

K+ -coupled

The bond energies associated with noncovalent attractions in the cell are too weak to resist disruption by thermal motion. However, cellular macromolecules can interact specifically AND strongly with each other (or fold by themselves) merely via such interactions. How is this possible?

Many weak bonds together in a complementary geometry can afford a strong binding.

Which of the following statements is TRUE?

Membrane lipids diffuse within the plane of the membrane.

Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport?

Nuclear transport receptors would be unable to release their cargo in the nucleus

Which of the following statements about vesicular membrane fusion is FALSE?

The GTP hydrolysis of the Rab proteins provides the energy for membrane fusion.

Which of the following statements about secretion is TRUE?

The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior.

Which of the situations below will enhance microtubule shrinkage?

addition of a drug that inhibits GDP to GTP exchange on free tubulin dimers

Which of the following could potentially affect the polarity of cell?

all the above

Tight junctions

are formed from claudins and occludins.

Lysozyme is an enzyme that specifically recognizes and hydrolyzes bacterial polysaccharides, which renders it an effective antibacterial agent. Which of the following mechanisms best describes the manner by which lysozyme lowers the energy required for its substrate to reach the transition-state conformation?

by altering the shape of the substrate to mimic the conformation of the transition state

Cholera toxin, a multi-subunit protein secreted by the bacterium Vibrio cholerae, gains entry to gut epithelial cells by binding to the glycolipid, GM1 ganglioside (diagrammed above). Cholera toxin most likely binds to the ___________ portion of GM1 ganglioside that was assembled In the ______________ and is present in the ______________ layer of the plasma membrane.

carbohydrate, lumen of the Golgi, non-cytosolic

Some proteins have α helices, some have β sheets, and still others have a combination of both. What makes it possible for proteins to have these common structural elements?

hydrogen bonds between atoms along the protein backbone

A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: Unfortunately, the grape juice is contaminated with proteases that attack some of the transport proteins in the yeast cell membrane, and the yeast cell dies. Which of the following is the most likely cause of the yeast cell's demise?

inability to import sugar into the cell

What unit of length would you generally use to measure a typical plant or animal cell?

micrometers

The γ-tubulin ring complex is to microtubules what _____ is to actin filaments.

the Arp 2/3 complex