Cell Membrane Quiz
Questions: 16 · 10 minutes
1. A researcher can remove a membrane protein only after disrupting the hydrophobic interior of the bilayer with detergent. What does this suggest?
The protein is attached only to carbohydrate chains outside the cell
The protein is freely dissolved in the cytoplasm
The protein is integral and embedded in the lipid bilayer
The protein is a peripheral protein held only by weak surface interactions
2. A white blood cell surrounds and takes in a bacterium by forming a membrane-bound vesicle. Which process is occurring?
Facilitated diffusion
Phagocytosis, a form of endocytosis
Osmosis
Exocytosis
3. Why do phospholipids spontaneously form a bilayer in water?
Their phosphate heads avoid water while their fatty acid tails attract it
Their hydrophilic heads face water while their hydrophobic tails cluster away from it
Their heads and tails are both hydrophobic, so water compresses them into two layers
Covalent bonds form between every phospholipid and the surrounding water
4. A hormone cannot cross the lipid bilayer but still changes activity inside its target cell. What most likely begins this response?
The hormone dissolves the membrane around the target cell
The hormone is converted into a phospholipid outside the cell
The hormone enters through any open ion channel
The hormone binds to a specific membrane receptor that triggers intracellular signaling
5. A permeable molecule reaches dynamic equilibrium across a membrane. What happens at equilibrium?
Molecules continue moving in both directions at equal overall rates
Every molecule stops moving across the membrane
The membrane becomes permanently closed to that molecule
All molecules gather on one side while maintaining equal pressure
6. What is the cell membrane's main role?
Regulating movement into and out of the cell while separating it from its surroundings
Storing most of the cell's hereditary information
Producing nearly all of the cell's ATP
Assembling amino acids into proteins
7. Some intestinal cells have many membrane folds called microvilli. How do these folds support absorption?
They decrease membrane fluidity so substances cannot escape
They eliminate the need for membrane transport proteins
They increase membrane surface area available for transport
They reduce the distance between the nucleus and mitochondria
8. Which substance would generally cross a pure phospholipid bilayer most easily without a transport protein?
A small nonpolar molecule such as oxygen
A sodium ion
A large polar glucose molecule
A charged amino acid
9. A gland cell packages a protein into a vesicle, which fuses with the plasma membrane and releases the protein outside. What is this process?
Pinocytosis
Exocytosis
Receptor-mediated endocytosis
Simple diffusion
10. In an animal cell membrane, what is one effect of cholesterol at relatively high temperatures?
It converts unsaturated fatty acids into saturated fatty acids
It makes the membrane freely permeable to ions
It removes membrane proteins to prevent denaturation
It restrains phospholipid movement and helps limit excessive fluidity
11. An animal cell is transferred to a solution with a higher concentration of nonpenetrating solute than the cytoplasm. What will most likely happen?
Solute rapidly enters until the cell bursts
Water leaves the cell, causing it to shrink
The cell stays unchanged because solute cannot cross
Water enters because the external solution is hypotonic
12. A sodium-potassium pump moves ions against their concentration gradients. What directly supplies the energy for this transport?
ATP hydrolysis
Water moving through aquaporins
The random motion of phospholipids
Oxygen diffusing across the membrane
13. An animal cell is placed in a solution with a lower solute concentration than its cytoplasm. What is the most likely immediate effect?
Solute leaves the cell, causing it to shrink
Water leaves the cell, causing it to shrink
Water movement stops because animal cells are isotonic by default
Water enters the cell, causing it to swell
14. Oxygen concentration is higher outside a cell than inside it. If the membrane is permeable to oxygen, what will most oxygen molecules do?
Enter only if a carrier protein uses ATP
Remain outside because gases cannot cross the phospholipid bilayer
Move out of the cell by osmosis
Diffuse into the cell down the concentration gradient
15. Two otherwise similar membranes are cooled. One contains more phospholipids with unsaturated fatty acid tails. How will that membrane generally respond?
It will become impermeable because unsaturated tails carry electric charges
It will become less fluid because double bonds form cross-links between phospholipids
It will remain more fluid because tail bends prevent tight packing
It will lose its bilayer structure because unsaturated tails dissolve in water
16. A glucose molecule moves into a cell through a carrier protein, down its concentration gradient, without ATP being used. Which process is this?
Endocytosis
Primary active transport
Facilitated diffusion
Simple diffusion through the lipid bilayer