Chapter 5 Launchpad

Which of the structures are part of the endomembrane system? A) the nuclear envelope B) The mitochondria or chloroplasts are not connected in any way to the endoplasmic reticulum, Golgi apparatus, or nucleus. C) peroxisomes D) mitochondria E) chloroplasts

A

During translation, the new polypeptides are often directed to specific parts of the cell by the presence or absence of short sequences of amino acids called signal sequences. Which peptides would you expect to find in the polypeptide that will eventually fold to become an ion channel protein? Select all that apply. A) a signal-anchor peptide B) an amino-terminal signal peptide C) no signal peptide D) an internal signal peptide

A, B

How do eukaryotic plant and animal cells differ from one another? A) Animal cells have mitochondria but not chloroplasts, and plant cells have chloroplasts but not mitochondria. B) Animal cells do not have chloroplasts and cell walls, and plant cells do. C) Animal cells have a plasma membrane, and plant cells have a cell wall. D) Animal cells have endoplasmic reticulum, and plant cells don't.

B

Imagine that you have two blades of grass. One is from a normal plant, and the other is from a mutant plant that cannot absorb water into its vacuoles. How will the structures of these two blades of grass compare? A) The grass blade from the mutant plant will appear taller than that from the normal plant. B) The grass blade from the mutant plant will appear limp compared to that from the normal plant. C) The grass blade from the mutant plant will be sturdier compared to that from the normal plant. D) The grass blades from the mutant and normal plant will appear identical.

B

Which of the substances would be an example of a peripheral membrane protein associated with the plasma membrane of a cell? A) MEK, an enzyme that activates other proteins in the cytoplasm B) Grb2, a protein that binds to the intracellular domain of the Epidermal Growth Factor Receptor when it is activated C) Myc, a transcription factor that binds to DNA and activates transcription of specific genes D) The Epidermal Growth Factor Receptor, which binds to signals outside the cell and phosphorylates proteins in the inside of the cell

B

A cell has a mutation that prevents it from breaking down unwanted proteins present in vesicles. Which cellular structure is most likely to be disrupted by this mutation? A) the endoplasmic reticulum B) the Golgi apparatus C) lysosomes D) the cytoskeleton

C

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations of salt (measured by molarity, M) and are separated by a membrane that is permeable to both salt and water. The salt and water will move through the membrane by diffusion. Which statement is true about the diffusion of these solutions? A) There will be a net movement of both salt and water from side B to side A. B) There will be a net movement of salt from side A to side B and no movement of water. C) There will be a net movement of salt from side B to side A and net movement of water from side A to side B. D) There will be a net movement of water from side A to side B and no movement of salt.

C. During diffusion, molecules move down their concentration gradient from regions of high concentration to those of low concentration. When salt is dissolved in water, the water dilutes the salt, but the salt also dilutes the water. The lowest water concentration would be where the salt concentration is highest.

Prokaryotes absorb their nutrients from the environment. However, many prokaryotes have cell walls. What can you conclude from this information? A) Prokaryotes produce all their own nutrients with enzymes in the cell wall. B) Prokaryotic cell walls do not need to allow nutrients to pass through them, because prokaryotes produce their own nutrients. C) Prokaryotes live in hypertonic environments. D) Cell walls are permeable, allowing nutrients to pass through.

D

In the kidney, glucose transport across the cell membrane is the result of a combination of two steps in active transport. The first step involves a primary active transport system performed by the sodium-potassium pump. It uses the energy from ATP hydrolysis to move sodium ions out of the cell and potassium ions into the cell. The second step involves a secondary active transport symporter that uses the energy in the sodium gradient created by the first step. This second step moves glucose, as well as sodium ions that move down their concentration gradient, into the cell. What would happen if the supply of ATP was depleted from the cell? What would happen if the rate of function of the sodium-potassium pump increased? A) The sodium-potassium pump would make less of a sodium gradient, but it would have no effect on the glucose transport. B) The sodium-potassium pump would be unaffected, and therefore, there would be no effect on glucose transport. C) The sodium-potassium pump would be unaffected, but the rate of glucose transport would increase. D) The sodium-potassium pump would make less of a sodium gradient, so less glucose could be transported across the membrane. E) The sodium-potassium pump would make a stronger sodium gradient, so more glucose could be transported across the membrane.

D, E

Which choice is considered an integral membrane protein? A) a protein attached to a transmembrane protein via hydrogen bonding B) a protein with its amino-terminus in the cytoplasm and its carboxy-terminus in the extracellular space. C) a protein attached to a phospholipid via ionic bonding with the head group of the lipid molecule D) a protein capable of diffusing throughout the cytoplasm of a cell

D. Integral membrane proteins are irreversibly embedded in the membrane. Some span the membrane with a hydrophobic bridge that connects the domains on either side of the membrane.

In intestinal epithelial cells, a transport protein moves the bulky, polar glucose molecules through the membrane into the cytoplasm, while simultaneously transporting Na+ through the membrane into the cell down its electrochemical gradient. Which example correctly describes this cotransport of glucose and sodium? A) primary active transport by a symporter B) primary active transport by an antiporter C) secondary active transport by an antiporter D) secondary active transport by a symporter

D. The gradient of sodium ions was formed by primary active transport and required energy. The energy stored in that gradient could then be used to get glucose through the membrane.

Researchers seldom find prokaryotic cells that are greater than 100 micrometers in diameter. Why would the size of prokaryotic cells be restricted? A) All of the answer choices are correct. B) Prokaryotic cells can exchange genetic information through pili, which are connections to nearby cells. C) Prokaryotic cells have multifunctional genes that can encode several proteins on a single mRNA. D) Prokaryotic cells do not have a phospholipid bilayer for a membrane. E) Prokaryotic cells must absorb all of their nutrients from their environment and therefore require a high surface area to volume ratio.

E

What would be found in the cells of a blade of grass but not in the cells of an insect feeding on that grass? A) endoplasmic reticulum B) cytoskeletal C) elements D) mitochondria E) chloroplasts F) nuclei

E

Which statement is true about the presence or absence of plasma membranes? A) Only animal cells have a plasma membrane. B) Plant cells and bacterial cells have a cell wall. C) Plant cells and animal cells have a plasma membrane, but bacterial cells do not. D) Plant cells and bacterial cells have a plasma membrane, but animal cells do not. E) All cells have a plasma membrane.

E

In order for phospholipids to form bilayers spontaneously in an aqueous environment, what should the pH be?

The pH should be approximately neutral so that the phospholipid heads remain charged and the molecules retain their amphipathic properties.

RNA molecules are transported from the nucleus to the cytoplasm in eukaryotes through:

nuclear pores