CELS-4-revision3

The presence of aquaporins in the plasma membrane is essential because:

Water requires ATP to pass through the lipid bilayer

The membrane is fully permeable to water without them

The hydrophobic core of the membrane restricts the movement of water molecules

Aquaporins actively pump water across the membrane

None

Which of the following statements about membrane proteins is true?

They only interact with the extracellular environment and do not contribute to intracellular processes

They are responsible for functions such as cell recognition, signal transduction, and structural support

They are embedded randomly within the plasma membrane and do not have specific orientations

They only function as transporters and do not participate in signal transduction

None

The ______ is a selectively permeable barrier separating the cell, primarily composed of a ______ bilayer with proteins that facilitate ______ transport.

Plasma membrane; lipid; active

Nuclear envelope; carbohydrate; passive

Cell wall; protein; facilitated

Plasma membrane; phospholipid; selective

None

Which of the following best describes the relationship between membrane proteins, transport mechanisms, and intracellular organization?

Membrane proteins involved in co-transport require ATP to move molecules across the membrane, utilizing the electrochemical gradient established by active transport to drive the simultaneous movement of two molecules in the same direction

Integral membrane proteins function solely in passive transport, allowing unrestricted movement of all small molecules across the plasma membrane, ensuring a balance between extracellular and intracellular environments

Membrane proteins are crucial for transport, cell signaling, and structural integrity, with specialized proteins functioning in passive diffusion, active transport, and receptor-mediated signaling, depending on cellular needs

Facilitated diffusion and active transport both require membrane proteins; however, facilitated diffusion can move molecules against their concentration gradient without ATP by leveraging channel proteins that undergo conformational changes

None

Which of the following is false about plasma membrane proteins?

Link the cytoskeleton and the extracellular matrix is what allows the cell to physically connect with the protein structure outside the cell

They are specific to cell type

Intercellular joining often occurs with the aid of glycoproteins (proteins with added sugars)

In signal transduction, some of the relay messages include grow and divide

None

Which of the following best explains why large polar molecules require transport proteins to cross the membrane?

The high permeability of the bilayer to water-soluble molecules prevents their uncontrolled entry

The membrane actively repels all molecules unless transport proteins are present

Polar molecules interact strongly with the lipid tails, making passive diffusion more efficient

The hydrophobic core of the bilayer prevents direct diffusion of polar molecules

None

The plasma membrane’s ability to regulate molecular traffic is primarily due to:

Its rigid and inflexible lipid composition

The presence of selective transport proteins

The exclusive role of carrier proteins in passive transport

The impermeability of the phospholipid bilayer to all molecules

None

Cholesterol within the plasma membrane plays a crucial role by:

Regulating fluidity by preventing solidification at low temperatures and excessive motion at high temperatures

Disrupting the bilayer to increase permeability to hydrophilic molecules

Preventing membrane proteins from functioning at high temperatures

Forming rigid structures that reduce all molecular movement

None

The hydrophilic regions of the membrane are oriented ______, while the hydrophobic regions face ______ due to the properties of phospholipid bilayer.

Toward the extracellular fluid; inward toward the bilayer’s core

Inward; outward

Outward; each other

Toward the cytoplasm; toward the extracellular matrix and cytoplasm

None

10.

Which of the following about membrane transport is false?

Passive diffusion requires no energy input and moves molecules down their concentration gradient

Active transport requires ATP to move molecules against their concentration gradient

Co-transport moves molecules passively without relying on another molecule’s gradient

Facilitated diffusion requires carrier proteins for transport

None