S3.6 Practice

What is the primary function of the cell membrane?

• To produce energy

• To maintain the cell's shape

• To regulate what enters and exits the cell

• To synthesize proteins

Answer explanation

The primary function of the cell membrane is to regulate what enters and exits the cell, maintaining homeostasis and allowing communication with the environment.

What type of molecule primarily makes up the cell membrane?

• Carbohydrates

• Phospholipids

• Proteins

• Nucleic acids

Answer explanation

The cell membrane is primarily composed of phospholipids, which form a bilayer that provides structure and regulates the movement of substances in and out of the cell. Carbohydrates, proteins, and nucleic acids play supporting roles.

What does "selectively permeable" mean regarding the cell membrane?

• All substances can pass through

• No substances can pass through

• Only certain substances can pass through

• It is impermeable to water

Answer explanation

"Selectively permeable" means that the cell membrane allows only certain substances to pass through, while blocking others. This is crucial for maintaining the cell's internal environment, making "Only certain substances can pass through" the correct choice.

Which of the following is a type of passive transport?

• Protein pumps

• Diffusion

• Endocytosis

• Exocytosis

Answer explanation

Diffusion is a type of passive transport where molecules move from an area of higher concentration to an area of lower concentration without the use of energy. In contrast, protein pumps, endocytosis, and exocytosis require energy.

Diffusion occurs when particles move:

• Against the concentration gradient

• From high to low concentration

• Using cellular energy

• Through protein pumps

Answer explanation

Diffusion is the process where particles move from areas of high concentration to areas of low concentration, seeking to equalize their distribution. Thus, the correct answer is 'From high to low concentration'.

Tags

NGSS.MS-LS2-3

What type of diffusion requires the assistance of membrane proteins?

• Simple diffusion

• Facilitated diffusion

• Osmosis

• Active transport

Answer explanation

Facilitated diffusion requires the assistance of membrane proteins to help transport substances across the cell membrane, unlike simple diffusion which occurs without such assistance.

Which of these processes does not require energy?

• Facilitated diffusion

• Endocytosis

• Active transport

• Exocytosis

Answer explanation

Facilitated diffusion is a passive transport process that does not require energy, as it relies on the concentration gradient. In contrast, endocytosis, active transport, and exocytosis all require energy to move substances across the membrane.

What is the role of aquaporins in the cell membrane?

• Transport of glucose

• Allow water to pass through

• Pump ions across the membrane

• Synthesize ATP

Answer explanation

Aquaporins are specialized proteins in the cell membrane that facilitate the transport of water molecules. They allow water to pass through the membrane efficiently, which is crucial for maintaining cellular hydration and homeostasis.

Osmosis is the movement of:

• Solute molecules

• Water molecules

• Proteins

• Ions

Answer explanation

Osmosis specifically refers to the movement of water molecules across a semipermeable membrane, driven by differences in solute concentration. Therefore, the correct answer is water molecules.

Tags

NGSS.MS-LS1-6

A cell in a hypertonic solution will:

• Swell

• Shrink

• Burst

• Stay the same

Answer explanation

A cell in a hypertonic solution has a higher concentration of solutes outside than inside. Water moves out of the cell to balance the concentration, causing the cell to shrink.