Transport

All else being equal, which of the following cells would be most efficient at diffusing CO2 waste from their cytoplasm to the outside environment?

• A
• B
• C
• D

Microvilli are tiny projections that extend from the cell in areas of the body like the small intestine.  What purpose might they serve? 

• Increased surfaced area for absorption of nutrients

• Decrease the volume of the cell to decrease the loss of nutrients

• Increase the volume of the cell to increase the SA:V ratio

• Decrease the surface area of the cell to increase absorption of nutrients

Tags

NGSS.MS-LS1-2

The movement of molecules directly across the phospholipid bilayer down their respective concentration gradients is best known as which of the following? Select all that apply.

• Passive transport
• Simple diffusion
• Primary active transport
• Receptor mediated endocytosis
• Active transport

Which phrase best describes all types of passive transport?

• Movement of substances into or out of the cell that requires transport proteins.
• Movement of substances across the membrane that does not require energy expenditure by the cell.
• Movement of water across the membrane in an isotonic solution.
• Movement of substances against their concentration gradients by transporters using energy from the cell.

Which of the following would increase the rate of water transport in a kidney cell? Check all that apply.

• Decreasing the density of potassium channels in the membrane.
• Adding many folds to the membrane to increase the SA:V ratio of the cell..

• Increasing the density of water channels (aquaporins) in the membrane.
• Increasing the density of the phospholipid bilayer by adding more saturated fatty acids.
• Increasing the fluidity of the bilayer by adding more cholesterol and unsaturated fatty acids.

Which of these is true about how particle size and electric charge affects a molecule's transport across a cell membrane?

• Large, polar molecules can cross the cell membrane as long as they are uncharged.

• Small, uncharged molecules like CO2 and N2O require protein channels to move across the membrane.

• Charged molecules like ions move across the membrane without any additional help from membrane proteins.

• Small, uncharged molecules like O2 and N2 cross the bilayer along their concentration gradients without assistance.

In the model below, how could the cell bring more of molecule A into the cytoplasm from the extracellular fluid?

• Gated protein channels specific to molecule A
• Molecule A will cross the membrane into the cell by simple diffusion.
• By a pump specific to molecule A, powered by ATP
• Molecule A will cross the membrane by osmosis.

In which situation would passive transport NOT need to use a protein for entry into a cell?

• K⁺ ions moving into the cell through a channel

• glucose being absorbed from the blood
• an ion flowing into a nerve cell to create an electrical potential
• oxygen moving into a cell after oxygen deprivation

Which of the following is an example of active transport.

• The movement of H+ ions through channels along their concentration gradient

• The transport of 3 Na+ ions out of the cell and 2 K+ ions into the cell by the sodium potassium pump against both of their gradients.
• The movement of glucose along its concentration gradient into the cell by glucose transporters.
• The movement of water out of the cell in a hypertonic environment

Proton pump inhibitors (PPI) irreversibly block the functioning of proton pumps in the cell membrane that use ATP to move H+ into the extracellular fluid from the cytoplasm. Which of the following would you expect to observe in a cell that has been treated with PPI?

• A decrease in the consumption of ATP by the cell.
• An increase in the size of the H+ concentration gradient across the membrane.
• An increase in the activity of secondary active transporters that are powered by an H+ concentration gradient.

• A decrease in the number of H+ ions inside the cell.