Biology: Chapter 5 Flashcards

All of the following are functions of the cell membrane EXCEPT:

1. transmitting signals.
2. participating in energy transfer.
3. being freely permeable to all substances.
4. regulating the passage of materials.
5. serving as surfaces for chemical reactions.

Which of the following statements concerning phospholipids is FALSE?

1. They have two distinct regions, one strongly hydrophobic and the other strongly hydrophilic.
2. They are amphipathic molecules.
3. They have cylindrical shapes that allow them to associate with water most easily as a bilayer structure.
4. They contain a polar organic group attached to a phosphate group.
5. They contain three fatty acids chains.

In a lipid bilayer, __________ fatty acid tails face each other within the bilayer and form a region that excludes water.

1. hypertonic
2. hyperosmotic
3. hypotonic
4. hydrophilic
5. hydrophobic

If phospholipids form a spherical structure when placed in water, then which of the following is the most logical conclusion about those phosopholipid molecules?

1. They are not amphipathic.
   They contain two fatty acid chains.
2. They are cone-shaped.
3. They form a bilayer.
4. Both their ends are hydrophilic.

A key discovery that weakened the Davson-Danielle "sandwich" model of cell membranes was that:

1. membrane proteins form a solid sheet on either side of the phospholipid bilayer.
2. membrane proteins form a solid sheet separating the phospholipid layer.
3. the phospholipids do not associate with each other in the hydrophobic region of membranes.
4. membrane proteins were not uniform and did not form flattened sheets.
5. membrane proteins occurred in regular organized patterns on the surface of membranes.

Who proposed the fluid mosaic model of cell membrane structure in 1972?

1. Davson and Singer.
2. Frye and Edidin.
3. Brown and Goldstein.
4. Singer and Nicholson.
5. Davson and Danielli.

What is meant by the term “fluid mosaic model”?

1. It is the diffusion of lipid-soluble substances through the lipid bilayer.
2. It is the movement of proteins within the phospholipid bilayer.
3. It is the solubility of water in the membrane.
4. It is the method of substance transport across the membrane.
5. It is the movement of proteins from the inner surface to the outer surface of the membrane.

In the experiment in which Frye and Edidin fused the plasma membranes of a mouse and a human cell, what happened to the membrane proteins?

1. They formed a spherical structure.
2. They formed a bilayer.
3. They moved laterally across the cell surface.
4. They flip-flopped from one layer to the other.
5. They reacted with cholesterol molecules on the membrane surface.

Vegetable oil is different from animal fat in that the phospholipids in vegetable oil have fatty acid tails that:

1. forms solids at room temperature.
2. lack double bonds.
3. are saturated.
4. interact via van der Waals forces.
5. bend at each double bond.

Cholesterol within membranes functions as a(n) __________ through its interactions with both hydrophobic and hydrophilic parts of phospholipids.

1. water blocker
2. pH buffer
3. energy source
4. temperature controller
5. fluidity buffer

Which of the following statements about lipid bilayers is FALSE?

1. They are self-sealing.
2. They are inflexible.
3. They spontaneously form closed vesicles.
4. They can fuse with other bilayers.
5. They resist forming free ends.

Integral proteins:

1. are weakly bound to the surface of the membrane.
2. are strongly bound to the cytosolic surface of the membrane.
3. have no hydrophobic portions.
4. are completely embedded within the lipid bilayer.
5. are amphipathic.

A transmembrane protein differs from other membrane proteins because it:

1. is covalently linked to the outer surface of the plasma membrane.
2. is a glycoprotein with carbohydrates attached.
3. is attached to the inside of the membrane by an ionic bond.
4. completely extends through the membrane.
5. is completely embedded within the membrane.

Peripheral proteins are linked to either surface of the plasma membrane by:

1. covalent disulfide bonds.
2. associating with fatty acids through hydrophobic interactions.
3. embedding in one side of the membrane and, thus, not extending through to the other side.
4. associating with glycoproteins on the inner membrane surface.
5. bonding to integral proteins through noncovalent interactions.

Integral proteins are:

1. manufactured in nucleus.
2. manufactured by the nucleolus.
3. made by ribosomes floating free in the cytoplasm.
4. made by ribosomes located on the rough endoplasmic reticulum.
5. made by ribosomes in the vesicles.

Biological membranes are normally permeable to:

1. large, hydrophilic molecules.
2. small, hydrophilic molecules.
3. large, hydrophobic molecules.
4. small, hydrophobic molecules.
5. ABC transporters.

Which of the following molecules is least likely to cross a cellular membrane by simple diffusion?

1. carbon dioxide
2. nitrogen
3. oxygen
4. potassium ion
5. water

An ABC transporter:

1. is a type of water channel.
2. uses the energy of ATP to transport solutes.
3. uses gated channels to transport ADP.
4. is present in kidney tubules and prevents dehydration.
5. is a type of porin.

Which of the following is not a characteristic of aquaporins?

1. They are transmembrane proteins.
2. They facilitate the rapid transport of water through the plasma membrane.
3. They are located in mammalian kidney tubules.
4. They respond to specific hormones.
5. They cause dehydration.

A bottle of perfume is opened on the opposite side of the room and within minutes you begin to smell the perfume. This phenomenon is a classic example of:

1. dialysis.
2. osmosis.
3. active transport.
4. facilitated diffusion.
5. simple diffusion.

The passive movement of a substance along its concentration gradient is termed:

1. active transport.
2. dialysis.
3. diffusion.
4. exocytosis.
5. osmosis.

Simple diffusion may involve the movement of __________ through the plasma membrane down a concentration gradient.

1. small polar molecules
2. small nonpolar molecules
3. large polar molecules
4. large nonpolar molecules
5. water

Which of the following membrane activities does NOT require the expenditure of energy by the cell?

1. active transport
2. osmosis
3. endocytosis
4. exocytosis
5. synthesis of more membrane

If the concentration of solutes in a cell is less than the concentration of solutes in the surrounding fluid, then the extracellular fluid is said to be:

1. hypertonic.
2. hypotonic.
3. isotonic.
4. stable.
5. amphipathic.