AP Bio membrane transport proteins practice questions

Define passive transport.

Movement of molecules across a membrane without energy input. - Examples: diffusion, osmosis.

Active transport requires what?

Energy, usually from ATP, to move substances against their concentration gradient.

True or False: Facilitated diffusion requires energy.

False. Facilitated diffusion uses transport proteins but does not require energy.

Compare simple diffusion and facilitated diffusion.

Simple diffusion: nonpolar molecules pass directly through lipid bilayer. Facilitated diffusion: polar/ionic substances use protein channels.

Fill in the blank: Osmosis is the diffusion of ___ across a selectively permeable membrane.

Water.

What is the primary function of channel proteins?

Facilitate the passage of specific ions or molecules across a membrane.

Primary active transport vs. secondary active transport.

Primary: directly uses ATP. Secondary: uses energy from primary transport to move other substances.

Name an example of osmosis in cells.

Red blood cells in hypertonic solutions shrink due to water loss.

True or False: Ion channels are specific to certain ions.

True. Ion channels allow specific ions to pass through, based on size and charge.

Describe the sodium-potassium pump.

An example of primary active transport that moves 3 Na⁺ out and 2 K⁺ into the cell per ATP.

Cause of endocytosis.

Cell membrane engulfs material, forming vesicles to bring substances into the cell.

What role do carrier proteins play?

Bind specific molecules and change shape to transport them across the membrane.

Define isotonic solution.

Solution with the same solute concentration as cell cytoplasm; no net water movement.

How does temperature affect membrane permeability?

Higher temperatures increase permeability due to increased fluidity of the lipid bilayer.

What is bulk transport?

Movement of large quantities of material across the cell membrane via vesicles.

Explain cotransport.

Simultaneous transport of two different molecules across a membrane via a single protein.

Define the role of carrier proteins.

Carrier proteins facilitate the passive or active transport of specific molecules across the membrane by changing shape.

True or False: Channel proteins require energy to function.

False - Channel proteins allow passive transport of ions and molecules without energy.

Compare carrier proteins and channel proteins.

Carrier proteins change shape to transport substances; channel proteins form openings allowing direct passage.

Fill in the blank: Aquaporins are specialized ___ for water transport.

proteins

What do transport proteins help maintain?

They help maintain concentration gradients across the cell membrane.

Describe the action of sodium-potassium pumps.

Sodium-potassium pumps actively transport 3 sodium ions out and 2 potassium ions into the cell, using ATP.

Implication of facilitated diffusion.

Facilitated diffusion allows polar molecules to cross membranes efficiently, driven by concentration gradients.

List two functions of membrane transport proteins.

- Transport nutrients - Maintain ion balance

What is the function of GLUT proteins?

GLUT proteins facilitate the transport of glucose across the plasma membrane via facilitated diffusion.

True or False: Active transport moves substances against their concentration gradient.

True - Active transport requires energy to move substances from low to high concentration.

Describe co-transport.

Co-transport uses the energy from one substance moving down its gradient to drive another substance against its gradient.

What is the role of ion channels?

Ion channels allow selective movement of ions like Na+, K+, Ca2+, or Cl- across the membrane.

Identify the energy source for active transport.

ATP is the primary energy source for active transport mechanisms.

Explain the importance of membrane potential.

Membrane potential is critical for nerve impulse conduction and muscle contraction, driven by ion transport proteins.

Facilitated diffusion example in cells?

Glucose transport into cells via GLUT proteins. - No energy required - Moves down concentration gradient

True or False: Aquaporins transport ions.

False. Aquaporins specifically facilitate water transport, not ions.

Compare active transport and passive transport.

Active transport requires energy (ATP) to move substances against their gradient, while passive transport does not and moves with the gradient.

Function of the sodium-potassium pump?

Moves 3 Na⁺ out and 2 K⁺ in. - Maintains cell potential - Uses ATP

Example of bulk transport?

Endocytosis allows cells to engulf large particles or fluids - Phagocytosis for solids - Pinocytosis for liquids

Fill in the blank: _____ transport does not require energy.

Passive transport

What drives osmosis?

The concentration gradient of water molecules - Water moves from low solute concentration to high.

Example of symport transport?

The sodium-glucose cotransporter uses Na⁺ concentration gradient to move glucose into the cell.

True or False: Ion channels are specific to their ions.

True. Ion channels selectively allow specific ions to pass based on size and charge.

What is secondary active transport?

Utilizes the energy from primary active transport to drive the movement of other substances against their gradient.

Example of exocytosis?

Neurotransmitter release from neurons. - Vesicles fuse with the membrane - Release signals to other neurons.

Cause → Effect: High glucose concentration outside the cell?

Glucose enters the cell via facilitated diffusion, increasing intracellular glucose levels.

What is the role of cholesterol in membranes?

Cholesterol maintains membrane fluidity, preventing it from becoming too rigid or too fluid.

Example of a transport protein involved in nutrient absorption?

Sodium-glucose symporter in intestinal cells facilitates glucose uptake with sodium.