AP Bio-Chapter 7

Multiple Choice

Which best describes a biological membrane?

• two layers of phospholipids with proteins embedded between the two layers

• a mixture of covalently linked phospholipids and proteins that determines which solutes can cross the membrane and which cannot

• two layers of phospholipids with proteins either spanning the layers or on the surface of the layers

• a fluid structure in which phospholipids and proteins move freely between sides of the membrane

• two layers of phospholipids (with opposite orientations of the phospholipids in each layer) with each layer covered on the outside with proteins

Multiple Choice

Which amino acid would most likely be present in the outer side of a transmembrane domain of an integral membrane protein?

• a charged amino acid like lysine

• a polar amino acid like serine

• a special amino acid like proline

• a hydrophobic amino acid like valine

• any of the above, with no preference

Multiple Choice

At a cocktail party with people moving around a large room, the doors to the room are like ______.

• energy

• membrane proteins

• DNA

• phospholipids

• none of the above

Multiple Choice

Which molecule will diffuse most quickly across a lipid bilayer membrane?

• H2O

• O2

• H2PO4-

• glucose

• Na+

Multiple Choice

Which part of the cell is most crucial for getting membrane proteins to their proper location?

• plasma membrane

• mitochondrion

• chloroplast

• Golgi Apparatus

• lysosome

Multiple Choice

Which statement about osmosis is correct?

• If a cell is place in an isotonic solution, more water will enter the cell than leaves the cell.

• Osmotic movement of water into a cell would likely occur if the cell accumulates water from its environment.

• The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis.

• If a solution outside the cell is hypertonic compared to the cytoplasm, water will move into the cell by osmosis.

• Osmosis is the diffusion of water from a region of lower water concentration to a region of higher water concentration.

Multiple Choice

A cell that has a contractile vacuole is likely, at times, to have

• too much membrane.

• too much water.

• too much salt.

• too little pigment.

• none of the above.

Multiple Choice

An artificial liposome, whose membrane contains no proteins, is loaded with a 0.03 M sucrose solution and put into pure water. Which best describes what will quickly happen?

• Since there are no membrane proteins, nothing will cross the membrane.

• Sucrose will diffuse out of the liposome.

• Water will diffuse down its concentration gradient into the liposome, causing it to burst.

• Water will enter the liposome, diluting the sucrose concentration there down to 0 M.

• The pressure of the surrounding solution will push water out of the liposome, causing it to shrink over time.

Multiple Choice

Two solutions with similar solute concentrations are separated by a membrane that only water can pass through. One solution (B) is of greater volume than the other (A). What will happen next?

• The pressure gradient will drive water to A, which will cause the solute concentration of B to increase.

• Water will pass to B, increasing its volume.

• Any water that passes to A will create tension on B, pulling the water back.

• The water will flow to A, down its pressure gradient, until the two sides achieve equal height.

• Since there is no concentration gradient present, there will be no net movement of water.

Multiple Choice

After an hour, a freshwater unicellular eukaryote dropped into seawater will be

• plasmolyzed

• swollen

• unchanged

• a or b; you can't tell from the question

• a or c; you can't tell from the question

Multiple Choice

How is a brick starting to fall from the fourth floor of a building most like a glucose molecule in a cell containing lots of glucose that is about to exit the cell?

• The brick needs a carrier.

• Both are moving down a potential energy gradient.

• Both are needed to build things.

• Both have mass.

Multiple Choice

Based on our model of the membrane, which statement would lose points on an exam?

• Glycoproteins tend to have oligosaccharides on their outward-facing side.

• Transmembrane proteins often bind with cytoplasmic proteins, but not with extracellular molecules.

• The combinations of phospholipids in the two faces of the membrane often differ.

• Phospholipids tend to move faster laterally along the membrane than do the proteins.

• Some transmembrane proteins function as active transport systems.

Multiple Choice

You are studying a pump protein in the lab. What should you order to make sure that the pump will operate?

• salt

• glucose

• DNA

• pure water

• ATP

Multiple Choice

A correct distinction between facilitated diffusion and active transport is that

• active transport requires conformational changes in the transport protein associated with the transport process, and facilitated diffusion does not.

• active transport requires an integral membrane protein to carry out the transport, and facilitated diffusion does not.

• facilitated diffusion requires a protein-lined pore in the membrane, and active transport does not.

• facilitated diffusion depends on an existing energy gradient working on the transported substance, while active transport makes such a gradient.

• facilitated diffusion requires cellular energy (often from ATP hydrolysis), but active transport does not.

Multiple Choice

Cells such as bacteria are taken up by other cells such as white blood cells by which mechanism?

• pinocytosis

• exocytosis

• receptor-mediated endocytosis

• phagocytosis

• facilitated diffusion

Multiple Choice

Receptor-mediated endocytosis produces vesicles that

• typically deliver the items they take up to the nucleus of the cell.

• carry macromolecules and cells for delivery to the lysosomal compartment.

• assist in the removal of certain items from the cytosol of the cell.

• when formed, cause there to be more total surface area available in the plasma membrane.

• have receptors that can indicated at their cytosolic side whether ligands are bound or not on their extracellular/lumen side.

Multiple Choice

You are studying a unicellular eukaryote recently discovered in pond water, and you notice that it contains many coated vesicles. Immunological studies show that the vesicles mostly lack transmembrane proteins. These cells probably do a lot of

• pumping

• pinocytosis

• receptor-mediated endocytosis

• phagocytosis

• b and c