Plasma Membrane and Passive Diffusion

TRUE OR FALSE: The phospholipid bilayers in cell membranes are formed by phospholipid molecules that self-arrange head-to-head.

• True

• False

Answer explanation

The phospholipid bilayer self-arrange tail-to-tail.

Which cell organelle determines what molecules can enter and leave the cell?

• Cytoplasm

• Nucleus

• Plasma membrane

• Vacuole

All of the following are principal components of the plasma membrane EXCEPT for:

• Carbohydrate

• Lipids

• Nucleic acids

• Proteins

Answer explanation

The principal components of the plama membrane are lipids, proteins, and carbohydrates.

Passive transport involves the movement of particles from an area of _____ concentration to an area of ______ concentration.

• HIGH, LOW

• LOW, HIGH

• LOW, LOW

• HIGH, HIGH

This image is an example of a phospholipid. Which describes the part of a phospholipid that is HYDROPHILIC?

• the lipid "tails"

• the phosphate "tails"

• the lipid "heads"

• the phosphate "head"

Which molecules are most likely to cross a cell's phospholipid bilayer by simple diffusion?

• Sugar molecules

• Water

• Carbon dioxide (CO2)

• Oxygen (O2)

• Potassium Ions

Which of the following accurately describes the end goal of diffusion?

• Molecules stop moving through the cell membrane

• Molecules move into a cell at the same rate as molecules move out of the cell.

• Molecules move into a cell faster than they move out of a cell.

• Molecules move out of a cell faster than they move into the cell.

Which of the following describes the difference between simple diffusion and facilitated diffusion through a cellular membrane?

• Simple diffusion moves particles from an area of low concentration to high concentration; facilitated diffusion moves particles in the opposite direction.

• Simple diffusion moves particles in the direction of the concentration gradient; facilitated diffusion moves particles against the concentration gradient.

• Simple diffusion moves particles through the phospholipid bilayer; facilitated diffusion moves only water across the phospholipid bilayer.

• Simple diffusion moves particles through the phospholipid bilayer of a cell membrane; facilitated diffusion moves particles through transport proteins.

Passive transport is called "passive" because it occurs WITHOUT

• cause.

• energy.

• a concentration gradient.

• a cell wall.

TRUE OR FALSE: Channel proteins are different from carrier proteins because channel proteins change their shape to transport the molecules to the other side of the plasma membrane.

• TRUE

• FALSE

Answer explanation

Carrier proteins change shape, after binding to their passenger molecule, to transport the molecule across the cell membrane.