The Plasma Membrane Review

What are the two parts of an oil molecule?

• Glycerol head and hydrophobic tail

• Glycerol tail and fatty acid head

• Hydrophobic tail and hydrophilic head

• Hydrophilic tail and hydrophobic head

Answer explanation

The correct answer is 'Glycerol tail and fatty acid head' because these are the two parts that make up a molecule of oil.

Imagine you're a scientist studying cell structures, and you come across the findings of Gorter and Grendel. What major discovery about cell membranes would you learn from their experiment?

• They are composed of a carbohydrate layer

• They are composed of a single layer of lipids

• They are composed of a lipid bilayer

• They are composed of a protein layer

Answer explanation

The Gorter and Grendel experiment revealed that cell membranes are composed of a lipid bilayer.

Imagine a hot summer day, how do cholesterol molecules help our cell membranes cope with the heat?

• Stabilize the membrane in high temperatures

• Facilitate cellular communication

• Stabilize the membrane in low temperatures

• Make the membrane more rigid

Answer explanation

Cholesterol molecules stabilize the cell membrane in high temperatures by preventing the fatty acid tails from packing too closely together, thus maintaining membrane fluidity.

Imagine a busy airport terminal. What is the function of the security checkpoints (analogous to protein channels) in the terminal's operation?

• Stabilize the structure of the terminal

• Facilitate communication between passengers and staff

• Provide entry ways for passengers and their luggage

• Act as customer service desks

Answer explanation

Protein channels in the cell membrane provide entry ways for molecules by allowing specific substances to pass through.

What is the function of glycoproteins in the cell membrane?

• Act as enzymes

• Provide entry ways for molecules

• Stabilize the membrane

• Facilitate cellular communication

Answer explanation

Glycoproteins in the cell membrane facilitate cellular communication by serving as recognition sites for other cells and molecules.

Imagine a cell in the human body. What allows its phospholipid membrane to maintain a stable yet fluid structure that is selectively permeable?

• Amphipathic nature

• Hydrophilic heads

• Glycerol backbone

• Hydrophobic tails

Answer explanation

Phospholipids have an amphipathic nature, with hydrophilic heads and hydrophobic tails, allowing them to form a stable bilayer that is fluid yet selectively permeable.

Imagine a bustling city where the cell membrane functions similarly to various city operations. What roles do proteins play in this urban landscape?

• Facilitating communication between buildings, connecting different structures, anchoring buildings to the ground

• Transportation services, functioning as city workers, transmitting signals for operations

• All of the above

• None of the above

Answer explanation

Proteins in the cell membrane have various functions including cell-cell recognition, intercellular joining, attachment to the cytoskeleton, transport, acting as enzymes, and signal transduction, so the correct answer is 'All of the above'.

What prevents the phospholipids from packing too closely together, maintaining the fluidity of the membrane?

• Unsaturated fatty acid tails

• Protein channels

• Cholesterol molecules

• Saturated fatty acid tails

Answer explanation

Unsaturated fatty acid tails prevent the phospholipids from packing too closely together, maintaining the fluidity of the membrane by introducing kinks in the tails.

Which molecules can diffuse across the cell membrane due to their size and nonpolar nature?

• Large, polar molecules

• Small, nonpolar molecules

• Large, nonpolar molecules

• Small, polar molecules

Answer explanation

Small, nonpolar molecules can diffuse across the cell membrane due to their size and nonpolar nature, making them the correct choice.

Imagine a plant absorbing water from the soil. How does this water pass through the cell membrane of the plant's root cells?

• Via aquaporins

• Through facilitated diffusion

• By simple diffusion

• Through protein channels

Answer explanation

Water passes through the cell membrane via aquaporins, which are specialized protein channels that facilitate the movement of water molecules.