Week 2

The random movement of molecules within a solution is referred to as: osmosis. transport. translation. diffusion.

diffusion

Week 2 Cell Membrane The beaker in the illustration contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to water but not to salt. What will occur in this container? diffusion of water from A to B but no diffusion of salt diffusion of salt from B to A, but not of water diffusion of water from B to A and of salt from A to B diffusion of both water and salt from B to A

diffusion of water from A to B but no diffusion of salt

The interior region of a phospholipid bilayer is characterized as: hydrophilic and polar. hydrophilic. hydrophobic. polar.

hydrophobic

Molecules that are _____________ and _____________ are able to move across the cell membrane via simple diffusion. hydrophilic; small hydrophilic; large hydrophobic; small hydrophobic; large

hydrophobic; small

As molecules move down their concentration gradient, from a more ordered state to a less ordered state, entropy: is decreasing. remains the same. is increasing.

is increasing.

Which eukaryotic organelle is associated with the breakdown of macromolecules? the Golgi apparatus mitochondria lysosome endoplasmic reticulum

lysosome

The lipid components of cellular membranes often include: phospholipids and cholesterol. fatty acids and cholesterol. phospholipids. phospholipids and fatty acids.

phospholipids and cholesterol.

A beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as shown below. Initially, the liquid levels on both sides are the same. After the system described above reaches equilibrium, what will be the concentration of glucose on side B? 1.0 M 0.5 M The answer cannot be determined from the information provided. 0.75 M

0.75M

Why does active transport of molecules across a membrane require ATP? An input of energy is needed to move all molecules across a membrane. An input of energy is needed to speed up the rate of facilitated diffusion. An input of energy is needed because the movement of molecules requires the synthesis of additional membrane. An input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration.

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

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

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

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

Which molecule would most likely require a transport protein to cross the plasma membrane of a red blood cell? O2 C6H12O6 H2O CO2

C6H12O6

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: Not change Increase Decrease

Decrease

Which of the answer choices correctly describes the movement of water across a selectively permeable membrane during osmosis? Either of these descriptions is correct and equivalent. The water will move from high water concentration to low water concentration. The water will move from low solute concentration to high solute concentration.

Either of these descriptions is correct and equivalent.

The image illustrates our understanding of how typical cell membranes are structured. Which line is pointing at a protein? line B line D line A line C

Line A

The image illustrates our understanding of how typical cell membranes are structured. Which arrow is pointing at the hydrophilic head group of a phospholipid? line D line A line C line B

Line B

The image illustrates our understanding of how typical cell membranes are structured. Which arrow is pointing at a cholesterol? line B line C line D line A

Line D

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

Lower

Week 2 Membrane Transport 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? Net movement of Waste out of the cell will continue indefinitely (nothing will change) Net movement of Waste out of the cell will stop immediately and then Waste will be transported into the cell Net movement of Waste out of the cell will continue for some time and then Waste will be transported into the cell 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 All net movement of Waste in or out of the cell will stop immediately

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

A container is divided into two compartments by a membrane that is fully permeable to water and small ions. Water is added to one side of the membrane (side A), and a 5% solution of sodium chloride (NaCl) is added to the other (side B). If allowed to reach equilibrium, which of the answer choices would you predict? The level of solution on side A will be higher than side B. The NaCl concentration on side A and side B will each be 5%. The NaCl concentration on side A and side B will each be 2.5%. The level of solution on side B will be higher than side A.

The NaCl concentration on side A and side B will each be 2.5%.

Although the phospholipid molecules can be in constant lateral movement, they very rarely flip from one side of the bilayer to the other. Which of the answer choices could explain this? The head groups are too large to fit between the interior fatty acid tails. The molecular attraction between the fatty acid tails is too strong. The cholesterol keeps the phospholipids on the correct side. The head groups are repelled by the hydrophobic membrane interior.

The head groups are repelled by the hydrophobic membrane interior.

Which of the types of molecules depicted in the figure is amphipathic? The molecular attraction between the fatty acid tails is too strong. The head groups are too large to fit between the interior fatty acid tails. The cholesterol keeps the phospholipids on the correct side. The head groups are repelled by the hydrophobic membrane interior.

The head groups are repelled by the hydrophobic membrane interior.

In the experiment that showed membrane fluidity, what was the purpose of shining a laser on the membrane? The laser light allows the dye to be seen with the microscope. The laser light makes the proteins fluorescent. The laser light destroys the dye fluorescence.

The laser light destroys the dye fluorescence.

A container is divided into two compartments by a membrane that is fully permeable to water but not to larger molecules. Water is added to one side of the membrane (side A), and an equal volume of a 5% solution of glucose is added to the other (side B). What would you predict will happen? The water level on side A will increase and on side B will decrease. Glucose will diffuse from side A to side B. Glucose will diffuse from side B to side A. The water level on side B will increase and on side A will decrease.

The water level on side B will increase and on side A will decrease.

Week 2: Osmosis A beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as shown below. Initially, the liquid levels on both sides are the same. After the system described above reaches equilibrium, what can you predict about the water levels? The water will be higher on side B than on side A. The water will be higher on side A than on side B. The water level will be the same on both sides.

The water will be higher on side A than on side B.

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? There will be a net movement of water from side A to side B and no movement of salt. There will be a net movement of both salt and water from side B to side A. There will be a net movement of salt from side A to side B and no movement of water. 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.

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.

Week 2 Review Questions 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? There will be a net movement of water from side A to side B and no movement of salt. There will be a net movement of both salt and water from side B to side A. 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. There will be a net movement of salt from side A to side B and no movement of water.

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.

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

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

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

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

A bacterial cell, a plant cell, and an animal cell have which structure in common? a vacuole a cell wall a cytoplasm a nucleoid a nucleus

a cytoplasm

The plasma membranes of some plant cells use transport proteins to move protons out of the cell against their concentration gradient. This is an example of: active transport. simple diffusion. passive transport. endocytosis. facilitated diffusion.

active transport.

The plasma membrane is composed of a phospholipid bilayer and associated proteins. What else is commonly found in the plasma membranes of animal cells? amino acids ethanol nucleic acids cholesterol

cholesterol

Simple diffusion of a molecule down its concentration gradient requires an input of energy to the system. true false

false

Which molecules can easily diffuse across a plasma membrane? proteins gases like O2 and CO2. large polar molecules small charged molecules, such as ions

gases like O2 and CO2.

All cells have: internal compartments. genetic information. a cell wall. a nucleus.

genetic information.

Some plant cells create a 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: passive transport. facilitated diffusion. osmosis. secondary active transport.

secondary active transport.

Which eukaryotic cell structure plays a role in protein trafficking and sorting? mitochondria vacuoles peroxisomes lysosomes the Golgi apparatus

the Golgi apparatus

Diffusion is best described as the random movement of molecules influenced by: the thermal energy of the environment and energy transferred from molecular collisions in the cell. the thermal energy of the environment and the width of the plasma membrane. the width of the plasma membrane of the cell.the thermal energy of the environment. energy transferred from molecular collisions in the cell.

the thermal energy of the environment and energy transferred from molecular collisions in the cell.

At equilibrium, there will be no net movement of molecules across the cell membrane. false true

true