IB Biology Topic B2.1: Membranes and Membrane Transport Questionbank

Hydrophobic interactions minimize exposure of fatty acid tails to water

Hydrogen bonds link adjacent phospholipids into sheets

Their polar heads repel each other, forcing tails together

Water molecules actively pull phosphate groups into alignment

They are fully embedded in both membrane layers

They have a fixed pore size that allows only small polar molecules through

Their interior shape and chemical environment match specific transported substances

They are permanently open and allow all solutes to pass through

It passively allows sodium and potassium ions to diffuse down their concentration gradients to establish an equilibrium.

It actively transports sodium and potassium ions using ATP, creating an electrochemical gradient critical for membrane potential.

It transports sodium ions into the cell and potassium ions out of the cell without energy expenditure.

It creates a uniform ion distribution inside and outside the cell, thereby preventing depolarization events.

More bilayers form because every region becomes hydrophilic

Fewer bilayers form because amphipathic character is reduced

Bilayers remain unchanged because only proteins determine assembly

Bilayers invert so non-polar groups contact water