LS7A WEEK 2

Which of the following molecules does NOT easily diffuse across a plasma membrane? a) both small and large polar molecules b) gases c) small polar molecules d) large polar molecules

d) large polar molecules

Phospholipase is an enzyme that cleaves the phosphate head group off a phospholipid molecule. The plasma membrane is not, however, permeable to the enzyme. Imagine a cell where phospholipid A is present in the layer of phospholipids facing the exterior of the cell, and phospholipid B is present in the layer of phospholipids facing the interior of the cell. After adding phospholipase to the medium in which the cell is growing, what would you expect to find in the fluid surrounding the cell? a) phosphate head groups from neither phospholipids A nor B b) the phosphate head group from phospholipid B only c) phosphate head groups from both phospholipids A and B d) the phosphate head group from phospholipid A only

d) the phosphate head group from phospholipid A only

The interior region of a phospholipid bilayer is characterized as:

hydrophobic

A protein that is temporarily associated with a biological membrane is a(n): a) peripheral membrane protein. b) transmembrane protein and an integral membrane protein. c) transmembrane protein. d) integral membrane protein.

peripheral membrane protein.

Why does active transport require ATP? a) An input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration. b) An input of energy is needed to speed up the rate of facilitated diffusion. c) An input of energy is needed to maintain the conformation of transport proteins. d) An input of energy is needed to both speed up the rate of facilitated diffusion and maintain the conformation of transport proteins.

a) An input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration.

Which one of the following molecules would MOST likely require a transport protein to cross the plasma membrane of a red blood cell? a) C6H12O6 b) O2 c) CO2 d) H2O

a) C6H12O6

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations (measured by molarity, M) and are separated by a membrane that is permeable to both salt and water. Side A has 0.2 M of Salt and Side B has 0.9 M of salt. Which of the following statements is TRUE? a) Side A is hypotonic relative to side B. b) Side A is isotonic relative to side B. c) Side A is hypertonic relative to side B.

a) Side A is hypotonic relative to side B.

In the figure below, the cell is _____ to the solution. If the membrane is permeable to water, but not to solutes, net movement of water will be _____ the cell. (Note that the units mM represent the total concentration of solute in the solution.) Inside the cell is 285 mM and outside the cell is 500 mM. a) hypotonic; out of b) hypertonic: out of c) hypotonic: into d) hypertonic: into

a) hypotonic; out of

Which eukaryotic organelle is associated with the breakdown of macromolecules? a) lysosome b) endoplasmic reticulum c) mitochondria d) the Golgi apparatus

a) lysosome

Which one of the following is NOT a component of an animal cell's plasma membrane? a) nucleic acid b) protein c) carbohydrate d) lipid

a) nucleic acid

Some plant cells take advantage of the high concentration of protons outside the cell to move solutes, such as sucrose, across the plasma membrane into the cell where the sucrose concentration is already relatively high. This type of transport is an example of: a) secondary active transport. b) osmosis. c) passive transport. d) facilitated diffusion.

a) secondary active transport.

Compared to when the Na+ channel is closed, how will the transport of Waste molecules change when the Na+ channel is open? The rate of Waste transport out of the cell will: a) Increase b) Decrease c) Not change

b) Decrease

The plasma membranes of some plant cells use transport proteins to move protons out of the cell against their concentration gradient (from areas of low proton concentration to areas of high proton concentration). This is an example of: a) simple diffusion b) active transport. c) endocytosis. d) facilitated diffusion. e) passive transport

b) active transport.

All cells have: a) a nucleus. b) genetic information. c) a cell wall. d) internal compartments.

b) genetic information.

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

c) Animal cells do not have chloroplasts and cell walls, and plant cells do.

During osmosis, water moves from a region of _____ to a region of _____. a) low solute concentration; high solute concentration b) high solvent concentration; low solvent concentration c) Both "high solvent concentration; low solvent concentration" AND "low solute concentration; high solute concentration" are correct answers. d) high solute concentration; low solute concentration

c) Both "high solvent concentration; low solvent concentration" AND "low solute concentration; high solute concentration" are correct answers.

The concentration of Waste molecules is ________ inside the cell compared to the outside. a) Higher b) About the same c) Lower

c) Lower

Why does a phospholipid on the cytoplasmic side of the cell membrane rarely flip to the extracellular side if both environments are polar? a) The cholesterol does not allow lipids to move. b) The two sides have different functions and thus the phospholipid would not function properly. c) The polar head group cannot pass through the nonpolar interior. d) The cytoplasmic phospholipid is too big to pass through the membrane.

c) The polar head group cannot pass through the nonpolar interior.

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations (measured by molarity, M) and are separated by a membrane that is permeable to salt. Side A has 0.2 M of Salt and Side B has 0.9 M of salt. Which of the following statements is TRUE? a) There will be a net movement of salt from side A to side B b) There will be no net movement of salt c) There will be a net movement of salt from side B to side A

c) There will be a net movement of salt from side B to side A

What will happen when the Na+ channel is open? a) There will be net movement of Na+ out of the cell through the channel b) There will be no net movement of Na+ through the channel c) There will be net movement of Na+ into the cell through the channel

c) There will be net movement of Na+ into the cell through the channel

A bacterial cell, a plant cell, and an animal cell have which of the following structures in common? a) cell wall b) nucleus c) cytoplasm d) nucleoid e) vacuole

c) cytoplasm

The random movement of molecules from areas of high concentration to low concentration is referred to as: a) osmosis. b) transport. c) diffusion. d) All of these choices are correct.

c) diffusion.

The lipid components of cellular membranes often include: a) fatty acids and cholesterol. b) phospholipids. c) phospholipids and cholesterol. d) phospholipids and fatty acids.

c) phospholipids and cholesterol.

Which of the following eukaryotic cell structures plays a role in protein trafficking and sorting? a) lysosomes b) mitochondria c) the Golgi apparatus d) the endoplasmic reticulum e) vacuoles

c) the Golgi apparatus

The beaker in the illustration below contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to both salt and water. Side A has 0.2 M of Salt and Side B has 0.9 M of salt. Which of the following will you observe immediately in this container? a) Net diffusion of water across the membrane, but not of salt. b) Net diffusion of water from B to A and of salt from A to B. c) No net diffusion of water or salt across the membrane. d) Diffusion of salt across the membrane, but not of water. e) Net diffusion of water from A to B and of salt from B to A. f) Net diffusion of salt from B to A, but no net diffusion of water

e) Net diffusion of water from A to B and of salt from B to A.

The diagram below shows a cell with three different membrane transport proteins. The Na+/K+ Pump is a primary active transporter and the Na+/Waste Co-transporter is a secondary active transporter. Arrows show the direction of net movement of molecules through the Pump and Co-transporter. The Na+ Channel can exist in either a closed state (no Na+ can pass through) or an open state (Na+ can pass through). Use this diagram to answer the questions below. What will happen to the net movement of Waste molecules if the Na+/K+ Pump stops working? a) Net movement of Waste out of the cell will continue indefinitely (nothing will change) b) Net movement of Waste out of the cell will continue for some time and then Waste will be transported into the cell c) All net movement of Waste in or out of the cell will stop immediately d) Net movement of Waste out of the cell will stop immediately and then Waste will be transported into the cell e) Net movement of Waste out of the cell will continue for some time and then all net movement of Waste in or out of the cell will stop

e) Net movement of Waste out of the cell will continue for some time and then all net movement of Waste in or out of the cell will stop

If cells had single-layer membranes like micelles, how would the structures of transmembrane proteins be affected? a) Transmembrane proteins would only possess hydrophilic regions. b) Transmembrane proteins would possess a hydrophilic region in the cell interior and a hydrophobic region in the extracellular space. c) Transmembrane proteins would only possess hydrophobic regions. d) The structures of transmembrane proteins would remain the same as if cells had lipid bilayers. e) Transmembrane proteins would possess a hydrophobic region in the cell interior and a hydrophilic region in the extracellular space.

e) Transmembrane proteins would possess a hydrophobic region in the cell interior and a hydrophilic region in the extracellular space.

The beaker in the illustration below contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to both salt and water. Side A has 0.2 M of Salt and Side B has 0.9 M of salt. Which of the following will you observe after a long time has passed? a) Net diffusion of water from A to B and of salt from B to A. b) Net diffusion of salt across the membrane, but not of water. c) Net diffusion of salt from B to A, but no net diffusion of water. d) Net diffusion of water across the membrane, but not of salt. e) Net diffusion of water from B to A and of salt from A to B. f) No net diffusion of water or salt across the membrane.

f) No net diffusion of water or salt across the membrane.