AP Biology : Understanding the Cell Membrane

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #128 : Ap Biology

When comparing two solutions with different solute concentrations, which of the following best defines the solution with the higher concentration of solute?

Possible Answers:

Isotonic

More soluble

Hypotonic

Hypertonic

Correct answer:

Hypertonic

Explanation:

Hypertonic is the correct answer for the solution with more solute in it. The root "hyper" means more; therefore, a hypertonic solution will have more solute. A hypotonic solution will have less solute in it. Isotonic solutions will have equal concentrations of solutes between the two solutions.

Example Question #129 : Ap Biology

When comparing two solutions with different solute concentrations, which of the following best defines the solution with the lower concentration of solute?

Possible Answers:

Hypotonic

Hypertonic

Less soluble

Isotonic

Correct answer:

Hypotonic

Explanation:

Hypotonic is the correct answer for the solution with less solute in it. The root "hypo" means less; therefore, a hypotonic solution will have less solute. A hypertonic solution will have more solute in it. Isotonic solutions will have equal concentrations of solutes between the two solutions.

Example Question #121 : Ap Biology

Which of the following terms is best defined as diffusion of water across a selectively permeable membrane?

Possible Answers:

Osmosis

Active transport

Concentration gradient

Membrane transfusion

Correct answer:

Osmosis

Explanation:

Osmosis is the process by which water will diffuse from the hypotonic side of the membrane to the hypertonic side. Water will naturally travel to areas with higher solute concentration in order to lower the concentration and make it equal to the concentration of its surroundings.

Example Question #61 : Cellular Biology

Which of the following best characterizes the process of osmosis?

Possible Answers:

Passive transport

Semi-active transport

ATP-driven transport

Active transport

Correct answer:

Passive transport

Explanation:

Osmosis is defined as a form of passive transport since it does not require an expenditure of energy. Osmosis follows a concentration gradient while active transport acts against the concentration gradient. Also, active transport requires energy and passive transport does not.

Example Question #62 : Cellular Biology

Which of the following terms is best defined as the tendency of molecules to spread out into available space?

Possible Answers:

Molecular motion 

Diffusion

Migration

Molecular spread

Correct answer:

Diffusion

Explanation:

Diffusion is defined as the spread of molecules into available space. The random nature of the movement of molecules in an open area means that molecules will seek to spread out—diffuse—evenly within a given area. This means that molecules will evenly distribute themselves when random assortment is permitted within a space.

Example Question #63 : Cellular Biology

Which of the following is best described as an example of a selective barrier in a cell?

Possible Answers:

Plasma membrane

Nucleus

Mitochondria

Cytoplasm

Correct answer:

Plasma membrane

Explanation:

The plasma membrane functions as a selective barrier to allow the flow of oxygen, nutrients, and wastes to and from the cell. The selectively permeable plasma membrane encloses the cytoplasm. The cytoplasm in turn contains the nucleus, mitochondria, and other organelles.

Example Question #64 : Cellular Biology

Cell membranes are permeable to ions and polar molecules. Which of the following enables the membrane to be permeable to these ions and molecules?

Possible Answers:

Ribosomes

Transport proteins

Desmosomes

Golgi apparatus 

Correct answer:

Transport proteins

Explanation:

Transport proteins span the exterior of the cell and allow substances to pass through the membrane. Some transport proteins are involved in facilitated diffusion, which is a type of passive transport. Other transport proteins are involved in active transport such as the sodium-potassium pump.

Example Question #65 : Cellular Biology

Which of the following is an example of passive transport?

Possible Answers:

Sodium-potassium pump

Electrogenic pump

Proton pump

Osmosis

Correct answer:

Osmosis

Explanation:

Osmosis is an example of passive transport. Osmosis does not use energy. Instead, it acts using the concentration gradient. The sodium-potassium pump, proton pump, and electrogenic pump are all examples of active transport. This means that they can pump solutes against their concentration gradients using cellular energy.

Example Question #66 : Cellular Biology

Which of the following is the term used for the model that describes the cell membrane as a mix of proteins bobbing about in a fluid bilayer of phospholipids?

Possible Answers:

Fluid protein model

Fluid membrane model

Fluid mosaic model

Mosaic membrane model

Correct answer:

Fluid mosaic model

Explanation:

The fluid mosaic model describes the mosaic structure of the cell membrane. According to this model, the cell membrane is composed of a variety of protein molecules randomly bobbing around in a sea of phospholipids. Due to phospholipid polarity, they naturally form a bilayer in accordance with their dual hydrophobic (tails) and hydrophilic (heads) natures.

Example Question #71 : Cellular Biology

Which of the following terms is used to describe the transmembrane proteins that span the hydrophobic interior of the cellular membrane?

Possible Answers:

Peripheral proteins

Transport proteins

Integral proteins

None of these

Correct answer:

Integral proteins

Explanation:

Integral proteins have both a hydrophobic region and hydrophilic region. The hydrophobic region allows them to sit within the cell membrane, while their hydrophilic regions face the aqueous solutions on either side of the membrane.

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